Hydraulic dampener for use on mine shovels

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.

BACKGROUND

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.

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.

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.

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

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.

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.

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.

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.

DESCRIPTION OF THE INVENTION

FIG. 7is a cross-sectional view of the right hand dampener assembly2taken along the line7-7inFIG. 3. Referring toFIG. 7, a rotatable actuator arm6R 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.

FIG. 1is a perspective schematic view of the right hand dampener2and the left hand dampener1wherein the dampeners are pinned (connected) to mounting structures on top of the bucket (not shown). The dampener arms6L,6R are connected to the bucket door linkage4L,4R and the linkage attaches to a door pivot arm5L,5R.FIG. 1illustrates a typical mounting configuration for the hydraulic dampeners. Pins3P,3P secure the dampener to the bucket structure3L,3R as illustrated inFIGS. 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's seat and when viewingFIG. 1from the left most part of the drawing sheet. Dampener assemblies1,2are attached to the top of the bucket utilizing existing mounting structures3L,3R on the bucket.

Dampener arm6L is connected to door linkage4L. Movement of the door creates rotational movement about the door pivot5A. The same movement also imposes a compression/tensile load through the door linkage4L. Door linkage4L loading is transmitted to the dampener arm6L and causes a rotational movement of the arm6L at the dampener1.

In reference to dampener2, dampener arm6R is connected to door linkage4R. Movement of the door creates rotational movement about the door pivot5A. The same movement also imposes a compression/tensile load through the door linkage4R. Door linkage4R loading is transmitted to the dampener arm6R and causes a rotational movement of the arm6R at the dampener2.

FIG. 1Ais a schematic view of the right hand dampener2mounted on top of the bucket3R with vertical and horizontal orientations shown from the perspective of lines1A-1A ofFIG. 1and with the bucket at rest or in the loading position with the door closed. Bucket door linkage5R is illustrated.

FIG. 1Bis a schematic view of the right hand dampener2mounted on top of the bucket with vertical and horizontal orientations shown from the perspective of lines1B-1B ofFIG. 1and with the bucket rotated in the dumping position and the door closed.

FIG. 1Cis a schematic view of the right hand dampener2mounted on top of the bucket, with vertical and horizontal orientations shown from the perspective of lines1C-1C ofFIG. 1, with the bucket rotated in the dumping position, and with the door open. Dampener arm6R is illustrated rotated counter clockwise to the door open position when viewingFIG. 1C. Also seeFIG. 7wherein dampener arm6R rotates counter clockwise to open the bucket door.

FIG. 2is a side view of a right hand dampener assembly from the perspective of line2-2inFIG. 1. Referring toFIG. 2, each dampener has a large bottom base plate7. Pins are slid through the large holes in the base plate to secure the dampener to the bucket structure3R,3L.

FIG. 3is a top view of a right hand dampener assembly from the perspective of line3-3inFIG. 1.FIG. 5is a top view of a right hand dampener similar toFIG. 3without the protective armor and dampener arm from the perspective of line5-5inFIG. 4. Referring toFIGS. 3 and 5, the dampener arm6R has a mechanical spline connection on shaft12to transmit torque from one component to the other. Referring toFIG. 3, a shaft end plate6A prevents the dampener arm6from sliding off the end of the shaft12.

Referring toFIGS. 2 and 3, the dampener has a couple pieces of armor8,9to protect various hydraulic fluid management components to be described later from damage during use. The primary manifold armor8has relief cut-outs to access fluid fill ports11as well as a removable cover plate10to access flow control valve14necessary for arm6positioning during installation of the dampener and which will be described later.

FIG. 4is a rear view of the right hand dampener assembly similar toFIG. 3without the protective armor and arm shown. Referring toFIGS. 4 and 5, under the armor8,9, the dampener has a primary hydraulic manifold13housing two pressure relief valves15,16, a flow control valve14, and a fluid diverter valve17. A hose21connects the top/primary manifold to a secondary accumulator manifold18. The accumulator manifold houses a manual flow control valve19and a pressure relief valve20. A second hose22connects the accumulator manifold18to the accumulator reservoir23. Both the accumulator manifold18and accumulator reservoir23are held in place via the protective armor9.

FIG. 6is a perspective view of the right hand dampener2from the perspective of line6-6inFIG. 5without one head24B, the protective armor8,9, and the dampener arm6R shown. Referring toFIGS. 5 and 6, the main dampener housing is composed of two heads24A,24B, a central body25, the shaft12, and an internal shoe28. Only one head is shown inFIG. 6.FIGS. 4 and 5illustrate heads24A,24B and the central body25. Shaft12is axially and radially held in place by the heads24A,24B but is free to rotate. As shaft12rotates, shaft vane12A rotates within the central body25. Shaft12and shaft vane12A are embodied within a single component. Shoe28, shoe seals28A, vane12A, and vane seals12B divide the central body25into two pressure-tight cavities29,30. Reference numeral29denotes the first central cavity and reference numeral30denotes the second central cavity.

The opening of the bucket door causes the shaft12to rotate in a clockwise (CW) direction as seen inFIG. 6and in a counter-clockwise (CCW) direction as viewed inFIG. 7. Referring toFIG. 7, a CCW rotation will cause a pressure increase in the first central cavity29and a decrease in pressure in the second central cavity30. High pressure in the first central cavity29will be transmitted to the first body port31leading to the primary manifold13.

FIG. 8Ais a cross-sectional view of the primary manifold13taken along the line8-8inFIG. 4and illustrates the door-opening condition. Referring toFIG. 8A, high pressure at the first body port31will pressurize second manifold passageway34. At this point, pressure and the majority of flow are blocked by pressure relief valves15,16. A small regulated amount of fluid is able to flow through the flow control needle valve14and into the first manifold passageway33where it can reenter the dampener second central cavity30via second body port32. However, the flow rate is negligible and pressure continues to increase in the second manifold passage34.

Referring toFIG. 8A, primary flow path50is indicated by a solid line in the door opening cycle. Primary flow path50extends during the door open cycle from the first body port31, through the door open pressure relief valve15, first manifold passage33, and into the second body port32. Dashed line51indicates a secondary minimal flow path from first body port31, second manifold passage34, across the exterior of pressure relief valve16, through needle valve14and into second body port32. Dashed line52indicates a tertiary minimal flow path through diverter valve17, manifold13, fitting35, and into the accumulator manifold18and accumulator reservoir23.

Fluid pressure acts against all internal surfaces on the high pressure side of the dampener including the shaft vane12A. Pressure multiplied by vane surface area multiplied by the average radial distance between the shaft vane12A and the shaft rotation axis equates to a “dampening” or counter-torque that works against the rotation of arm6and shaft12. Internal pressure will continue to rise until the opening pressure of relief valve15is reached. At that point, fluid can flow from the second manifold passageway34to the first manifold passageway33by traveling through the door open relief valve15. Fluid flows from the first manifold passageway33, through the second body port32, and into the dampener housing second internal cavity30. 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.

The developed torque from the dampener can be adjusted. Referring toFIG. 8A, the opening pressure of the door open pressure relief valve15and the opening pressure of the door close pressure relief valve16directly 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 valve15,16are increased by turning the valve15,16adjustment screw CW and reduced by turning the adjustment screw CCW. The valves15,16and their adjustment screws are easily accessed by removing the primary manifold armor8. This feature increases the flexibility of the dampeners. The same dampener can be used on multiple bucket platforms with the resistance torque adjusted accordingly.

FIG. 8Bis a cross-sectional view of the primary manifold13taken along the line8-8inFIG. 4which illustrates the door closing condition. The closing of the bucket door creates a CCW rotation of the shaft as seen inFIG. 6and CW as seen inFIG. 7. Referring toFIGS. 7 and 8B, this creates high pressure in the second central cavity30and low pressure in the first central cavity29. High pressure in second central cavity30pressurizes second body port32and first manifold passageway33. Referring toFIG. 8B, at this point fluid pressure and the bulk of fluid flow are stopped by the door close pressure relief valve16and the door open pressure relief valve15. A small quantity of hydraulic fluid is able to flow61through the flow control needle valve14where it can reenter the dampener via first body port31and then into first central cavity29which is at relatively low pressure. In addition, a small quantity of fluid can also pass through the diverter valve17, manifold13, and fitting35where it can then travel to the accumulator manifold18and accumulator reservoir23. However, fluid loss through the flow control valve14and diverter valve17is negligible and fluid pressure continues to rise in the first manifold passageway33. Fluid pressure acts on all internal surfaces on the high pressure side of the dampener including the shaft vane12A. Fluid pressure multiplied by the shaft vane12A surface area multiplied by the average radial distance from the shaft vane12A 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 cavities30,32, and33until the opening pressure of the door close pressure relief valve16is reached. At that point fluid is able to flow from second body port32, into first manifold passageway33, through relief valve16, through second manifold passageway34which is at low pressure, through the first body port31, and into the first central cavity29which is at low pressure. Arm6, shaft12, and shaft vane12A rotation as well as the dampening torque continue until the door comes to a stop.

Referring toFIG. 8B, primary flow path60is indicated by a solid line in the door close cycle. Primary flow path60extends through second body port32, first manifold passageway33, door close relief valve16, second manifold passageway34, and first body port31. Dashed line61indicates a secondary minimal flow path through needle valve14, across the exterior of door close relief valve16and into the first body port31. Dashed line62indicates a tertiary minimal flow path through diverter valve17, manifold13, and fitting35to the accumulator manifold18and accumulator reservoir23.

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 valves26have been installed in either face of the shaft vane12A. SeeFIGS. 6, 7, 12, 12A, and 12B.FIG. 12is an illustration of the dampener shaft12such its overall design can be seen.FIG. 12Ais a section view of the shaft vane12A along the line12A-12A inFIG. 12.FIG. 12Bis a section view of the shaft vane12A along the line12B-12B inFIG. 12. The pressure valves26sense pressure on the opposite sides of vane12A from which they are installed. Once pressure reaches the opening pressure of the valves26, fluid is able to flow into the valves26, through the vane passageways27, and out the opposite side of the vane to the low pressure cavity. In this way, fluid is able to bypass the external primary manifold13and 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 manifold13described previously. The added flow capacity reduces internal pressure and related over-pressurization damage. The shaft vane12A pressure relief valves26are installed in opposite faces of the vane such that the dampener has protection from pressure spikes in either shaft rotation direction.

The pressure relief valves26opening pressure is factory-set near the maximum recommended pressure and is not accessible or adjustable in the field. Because of this, the shaft vane valves26also help to protect the dampener from excessive pressure adjustment of the primary manifold13pressure relief valves15,16. The primary manifold13pressure relief valves15,16can 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 valves15,16will cause an increasing amount of fluid to be diverted through the shaft vane valves26thereby reducing potential damage from maladjustment of the external valves15,16.

Referring toFIG. 7, channels28B,28C are illustrated in shoe28and these facilitate flow through the first body port31and second body port32. Shoe stop28D engages vane12A preventing over travel of vane12A and pressure relief valves26. In this way relief valves26do not engage the shoe28.

The invention incorporates structure to prevent over-pressurization from heat. As the dampeners are cycled, heat is generated as fluid flows across the relief valves15,16, and26, seeFIGS. 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.

The dampeners transform the kinetic energy removed from the swinging door into heat at the dampener pressure relief valves15,16, and26. 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 vane12A. 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.

The invention moves small quantities of oil to an external accumulator reservoir23, seeFIGS. 4, 6, 7, 10A, and 10B. Referring toFIGS. 8A and 8B, whenever first manifold passageway33is suitably pressurized (pressure higher than that found in accumulator reservoir23), diverter valve17allows fluid to move to and through the fitting35where it travels by way of conduit21(hose) to a secondary accumulator manifold18, through a second conduit22(hose), and then to the external accumulator reservoir23. The diverter valve17is adjusted such that when the manifold first passageway33is suitably pressurized, a small metered stream of fluid is allowed to pass into the manifold fitting35. The accumulator downstream from manifold fitting35, will not experience large pressure variations in the dampener. In addition, the diverter valve17prevents 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 passageway33will be pressurized for a longer period of time and more fluid will be diverted to the accumulator reservoir23. Proper dampener fluid level is maintained by the constant metering-out of fluid to the accumulator reservoir23, and return of fluid from the accumulator to the dampener.

It is specifically envisioned that conduits other than hoses may be used to interconnect the fittings35,36,37, and23E. For instance, and without limitation, the conduit could be metal tubing, a metal reinforced hose, or braided metal conduit.

FIG. 10Ais a cross-sectional view of the accumulator reservoir23taken along the line10-10inFIG. 5as it appears upon initial start-up when the dampener is at ambient temperature. The accumulator23is composed of a central cylindrical body with heads23H,23H on both sides thereof The interior of the accumulator is separated into two pressure tight cavities by a moveable/sliding piston23D. One side of the piston23D the accumulator is full of compressed gas23B. On the other side of the piston, the accumulator is full of hydraulic oil23A. The gas23B is pressurized nitrogen gas which is introduced through the gas charge fitting23C 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 piston23D, and, to pressurize the hydraulic oil23A 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 valves15,16,26opening 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 piston23D 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 conduits21,22and the accumulator manifold18.

FIG. 10Bis a cross-sectional view of the accumulator reservoir23taken along the line10-10inFIG. 5as 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-side23A of the accumulator. Due to reduction of volume and higher temperature, the gas23B pressure rises and imposes a larger force on the piston than on initial start-up. The piston23D in turn transmits this force to the hydraulic fluid23A. The pressure imposed on the fluid23A will attempt to force it to a lower pressure area. As such, some of the fluid in the accumulator23flows 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 valves15,16,23pressure 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.

FIG. 9is a cross-sectional view of the accumulator manifold18taken along the line9-9inFIG. 7. Referring toFIGS. 9 and 11, hydraulic fluid leaves the dampener via fitting35on the primary manifold13. From there it travels down conduit21where it enters the accumulator manifold18via fitting36. Inside the manifold18, the fluid travels through passageway34A and then out again via fitting37where it then travels down conduit22and into the accumulator reservoir23. As discussed previously, as the dampener works, heat is generated and the hydraulic fluid expands into the accumulator reservoir23, 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 manifold18. 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 valve19is installed in the accumulator manifold18. The valve19can 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 fitting38thereby reducing internal pressure and making the dampener safer to service. In addition, the invention incorporates another pressure relief valve20into the accumulator manifold18. The valve20senses the difference in fluid pressure between the accumulator side of the system, specifically in passage34A in the accumulator manifold, and compares it to atmospheric pressure. If the pressure differential exceeds that of the open pressure of the relief valve20, fluid will automatically be sent out of the dampener via fitting38until 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.

Referring toFIG. 1, the invention incorporates a feature to aid attachment of the arm6to the door linkage4. The manifold armor8has a removable cover10as seen inFIG. 3. Removing the cover plate10allows the installer access to the flow control valve14as seen inFIG. 5, 8A, and 8Bwhich is adjustable. Backing-off the adjustment screw allows fluid to travel freely between manifold passages33,34without building pressure, and counter-torque, referenceFIGS. 8A and 8B. As a result the shaft12and arm6are able to freely rotate and allows the installer to line-up the arm6with the door linkage4. After installation, the adjustment screw is fully tightened and then backed-off a specified fraction of a turn.

The invention allows door travel even when dampener internal pressures are not sufficient to open relief valves15,16, and26. 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 toFIGS. 8A and 8B, in this scenario, the pressure inside the manifold13lowers to a point below the opening pressure of the relief valves15,16, and26and flow through them is stopped. However, the flow control valve14when 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 shaft12, dampener arm6, 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.

1left hand dampener2right hand dampener3L bucket structure to mount dampener3R bucket structure to mount dampener3P pins securing the dampener to the bucket structure3L,3R4L bucket linkage arm to connect dampener arm6L to bucket door mounting arm5L4R bucket linkage arm to connect dampener arm6R to bucket door mounting arm5R4P pin to connect dampener arm to bucket linkage arm5A door pivot5L bucket door mounting arm5R bucket door mounting arm5P pin to connect door mounting arm to bucket linkage arm6A dampener arm end plate6L dampener arm6R dampener arm7dampener mounting base8primary manifold and valve armor9accumulator reservoir and accumulator manifold mounting and protective armor10arm position valve access plate11dampener oil fill ports12vane shaft one piece assembly12A shaft vane12B shaft vane seal13primary manifold14arm position valve15door open pressure relief valve16door close pressure relief valve17fluid diverter valve18accumulator manifold19manual pressure relief valve20accumulator system pressure relief valve21primary manifold to accumulator manifold supply/return hose22accumulator manifold to accumulator reservoir supply/return hose23hydraulic oil accumulator reservoir23A hydraulic oil side of accumulator23B pressurized gas side of accumulator23C gas charge valve23D movable piston23E accumulator oil inlet fitting23H accumulator head24A dampener head24B dampener head25dampener central body26vane pressure valves27vane pressure valve relief passages28shoe28A shoe seal28B,28C channels in shoe28D stop29first central cavity30second central cavity31first body port32second body port33first manifold passageway34second manifold passageway34A passageway in the accumulator manifold1835diverter valve fitting36accumulator manifold inlet fitting37accumulator manifold outlet fitting38accumulator manifold overflow fitting50primary flow path during door open cycle through first body port31, door open pressure relief valve15, first manifold passageway33, and into second body port3251dashed line indicating secondary minimal flow path52dashed line indicating a tertiary minimal flow path through diverter valve17, manifold13, and fitting35to the accumulator manifold18and accumulator2360primary flow path during door close cycle through second body port32, first manifold passageway33, door close relief valve16, second manifold passageway34, and into body first port3161dashed line indicating secondary minimal flow path62dashed line indicating a tertiary minimal flow path through diverter valve17, manifold13, fitting35, and onto accumulator manifold18and accumulator2370primary flow path in accumulator manifold18, fluid enters via fitting36, through passageway34A, and exits to accumulator via fitting3771dashed line indicating a secondary flow path used when high pressure is found in the accumulator-side of the system, fluid travels through passageway34A, into pressure valve20, and exits the manifold and dampener via fitting38.72dashed line indicating a tertiary flow path used when pressure in accumulator-side of the system is manually reduced, fluid travels through passageway34A, into flow valve19, and exits the manifold and dampener via fitting38