阅读说明：本技术 空间受约束的混合线性促动器 (Space constrained hybrid linear actuator ) 是由 D·克里斯多佛·欧里诺 于 2019-10-15 设计创作，主要内容包括：提出了一种电动马达驱动的滚动元件螺杆线性促动器,其与液压促动器协作地工作并共享若干部件。这通过集成螺杆驱动的集成螺母活塞组件来实现。组合电动螺杆驱动促动器的使用也可以降低对冗余液压系统的需求,从而导致消除了50％的连接器、阀、管道、过滤器等,但仍是100％冗余的。附加的优点在于,两个驱动系统在技术上是独立的,因此不会由于相同的部件缺陷或故障点而均故障。如果状况需要的力超过液压促动器单独产生的力,则也可以同时使用这些系统。(An electric motor driven rolling element screw linear actuator is presented which works in cooperation with a hydraulic actuator and shares several components. This is achieved by an integrated nut and piston assembly that integrates the screw drive. The use of a combination electric screw drive actuator may also reduce the need for redundant hydraulic systems, resulting in the elimination of 50% connectors, valves, piping, filters, etc., but still 100% redundant. An additional advantage is that the two drive systems are technically independent and therefore do not both fail due to the same component defect or failure point. These systems may also be used simultaneously if the conditions require a force that exceeds the force generated by the hydraulic actuator alone.)

1. A hybrid linear actuator comprising:

a first drive assembly, the first drive assembly comprising:

an electric drive motor having an output shaft;

a drive screw attached to the output shaft;

a drive nut threadedly connected to the drive screw; and

an output rod having two ends, a first end attached to the drive nut such that rotation of the drive screw advances or retracts the output rod, and a second end attachable to a linearly actuated valve;

a second drive assembly, the second drive assembly comprising:

a hydraulic cylinder, a hydraulic cylinder and a hydraulic cylinder,

a piston disposed in the hydraulic cylinder and linked to the output rod, an

A hydraulic pump fluidly connected to the hydraulic cylinder and operable to selectively pressurize the hydraulic cylinder on either side of the piston, thereby changing the position of the piston within the hydraulic cylinder, thereby extending and retracting the output rod;

wherein the drive screw is at least partially disposed within the hydraulic cylinder and is of unitary construction.

2. The linear actuator of claim 1 wherein the piston within the hydraulic cylinder is operable to rotate the drive screw.

3. The linear actuator of claim 1 further including a disengagement mechanism interposed between said drive screw and said output shaft of said electric drive motor, said disengagement mechanism operable to selectively couple and decouple said drive screw and said output shaft.

4. The linear actuator of claim 1 wherein the drive screw and the output rod are coaxial.

5. The linear actuator of claim 1 wherein the output rod includes a hollow interior and wherein the drive screw extends into the hollow interior of the output rod.

6. The linear actuator of claim 1 wherein the drive nut is disposed within the hollow interior of the output rod.

7. The linear actuator of claim 1 wherein the actuator has a third drive assembly including a hydraulic accumulator fluidly connected to the hydraulic cylinder and operable to selectively pressurize the hydraulic cylinder on at least one side of the piston.

8. A compact hybrid linear actuator comprising:

a hydraulic cylinder having an inner chamber, a proximal end, and a distal end;

an output rod extending from the distal end of the hydraulic cylinder, the output rod having a proximal end and a distal end;

a piston on the proximal end of the output rod, the piston disposed within the inner chamber of the hydraulic cylinder; the piston divides the inner chamber of the hydraulic cylinder into a first pressure chamber and a second pressure chamber;

a threaded bore disposed in the first pressure chamber of the hydraulic cylinder; the threaded bore is arranged in a fixed, non-rotatable relationship with respect to the output rod; and

a drive screw disposed in the first pressure chamber and mounted into the threaded bore such that rotation of the drive screw moves the output rod.

9. The linear actuator of claim 8 wherein the output rod further includes a hollow interior, wherein a distal end of the drive screw extends into the hollow interior of the output rod.

10. The linear actuator of claim 8 wherein a proximal end of the drive screw extends from the proximal end of the hydraulic cylinder.

11. The linear actuator of claim 8 further including an electric motor having an output shaft linked to the proximal end of the drive screw by a drive system.

12. The linear actuator of claim 8 wherein the drive system includes one of a belt, a chain, and a gear.

13. The linear actuator of claim 8 wherein the drive system includes a disengagement mechanism operable to selectively couple and decouple the output shaft with the drive screw.

14. The linear actuator of claim 8 further comprising:

a first valve fluidly connected to the first chamber, the first valve operable between an open position and a closed position;

a second valve fluidly connected to the second chamber, the second valve operable between an open position and a closed position.

15. The linear actuator of claim 14 further including a hydraulic pump fluidly connected to the first and second valves.

16. A linear actuator having a redundant power source for use in a spatially constrained region, comprising:

an output rod having a proximal end and a distal end; the output rod having a hollow channel extending from a proximal end of the output rod toward a distal end of the output rod;

a first drive assembly comprising:

a drive nut disposed in a non-rotatable and fixed position relative to the output rod,

a drive screw mounted in the drive nut such that the drive screw extends into the hollow channel of the output rod, an

An electric drive motor having an output shaft linked to the drive screw such that rotation of the output shaft rotates the drive screw, thereby extending and retracting the output rod;

a second drive assembly comprising:

a hydraulic cylinder, a hydraulic cylinder and a hydraulic cylinder,

a piston disposed in the hydraulic cylinder and linked to the output rod, an

A hydraulic pump fluidly connected to the hydraulic cylinder and operable to selectively pressurize the hydraulic cylinder on either side of the piston, thereby changing the position of the piston within the hydraulic cylinder, thereby extending and retracting the output rod.

17. A compact hybrid linear actuator comprising:

an output rod;

a first drive assembly comprising:

a drive nut linked to the output rod,

a drive screw mounted into the drive nut,

an electric drive motor having an output shaft linked to the drive screw such that rotation of the output shaft rotates the drive screw, thereby extending and retracting the output rod;

a second drive assembly comprising:

a hydraulic cylinder, a hydraulic cylinder and a hydraulic cylinder,

a piston disposed in the hydraulic cylinder and linked to the output rod, an

A hydraulic pump fluidly connected to the hydraulic cylinder and operable to selectively pressurize the hydraulic cylinder on either side of the piston, thereby changing the position of the piston within the hydraulic cylinder, thereby extending and retracting the output rod,

wherein the first drive assembly and the second drive assembly are individually capable of extending and retracting the output rod upon failure of the other drive assembly; and is

Wherein the output rod includes a hollow interior, and wherein the drive screw extends into the hollow interior of the output rod.

18. The compact hybrid linear actuator of claim 17 wherein said hydraulic fluid and said drive screw are in the same housing.

19. The compact linear actuator of claim 17 wherein the first drive assembly and the second drive assembly are operable simultaneously to increase thrust on the output rod.

20. The compact linear actuator of claim 17 wherein the thrust force generated on the piston by hydraulic pressure is permitted to passively back drive the screw in the first drive assembly when the second drive assembly is used to generate thrust force to move the piston during extension or retraction of the rod.

Technical Field

The present invention relates to actuators, and in particular to actuators that must operate in a space-constrained environment and where the function of the actuator is critical.

Background

In the oil and gas industry, refining consists of a combination of various refining processes for refining crude oil. Some processes aim at upgrading heavy oils. One such process is commonly referred to as fluid cracking, or more specifically, Fluid Catalytic Cracking (FCC) and/or Flexi Coker (Flexi Coker). Both of these processes are important refining processes due to the ability to refine crude oil into a high proportion of high value, high octane gasoline. These two processes are run continuously for 24 hours a day for 5 to 7 years or more.

Typically, fluid cracking utilizes a catalyst (small sand-like particles) which allows coke to form on the catalyst surface during the process. The coked catalyst is then allowed to flow to another stage of the process where coke particles are burned off (FCC) or gasified to higher grade products (flexicoking).

The process is carried out by "fluidizing" the catalyst with steam, thereby allowing the catalyst to flow from one stage of the process to the other. Control of the flow of these fluidized particles is critical to both the efficiency and safety of the process. For FCC processes, the proportion of catalyst flow must be precisely controlled to maximize efficiency. Another part of the process that is critical to the efficiency of operation is the management of the exhaust gas stream and the regenerator flue gas.

It is important that in the event of an accidental shut down or failure to control the process, the flow of catalyst, exhaust gas stream and flue gas must be controlled at all times in chaotic conditions, or that the valve must be immediately valved to a predetermined position, opened closed or partially opened. Failure of the valve to properly react to a particular upset condition can lead to an explosion, which can have catastrophic consequences to the refinery, personnel, and surrounding community.

In some cases, the flow of catalyst, exhaust gas stream and flue gas vapor is regulated if by various types of valves such as slide valves, plug valves, butterfly valves, and the like. The accuracy of controlling the catalyst flow requires that the valve must be able to be accurately positioned at high speed.

It is critical to always ensure the operation of the FCC unit with the ability to control the position of the gate. Due to the critical requirement of having the ability to position the valve in any situation, the system must be designed with redundant layers. This is to ensure that valve positioning is always possible even in the event of failure of one or more components, and that a backup system/component will be immediately available to assume the primary responsibility of positioning the valve as required.

To achieve these operational requirements, FCC spools have traditionally relied on linear hydraulic actuators. The linear actuator is paired with a hydraulic pump, a reservoir, and associated valves needed to control the flow and pressure of fluid to the hydraulic cylinders. The system including the pump, reservoir, valves, filters and control IO is commonly referred to as a "hydraulic power unit".

Actuators used to activate valves used in petroleum refineries are often subject to dimensional constraints. The valve is typically located above the ground on the platform. The actuator for stroking the valve is typically located at the edge of the platform or against the machine. As a result, a linearly actuated valve may no longer be formed, or the actuator may extend over the edge of the platform and make maintenance very difficult. In addition, the position of the hydraulic power unit is limited, and sometimes it is necessary to make a change in design.

Disclosure of Invention

Some embodiments of the present invention utilize an electric motor driven rolling element screw linear actuator that occupies the same space as a hydraulic actuator. This is achieved by integrating the screw drive nut directly with the piston and seal present in the hydraulic cylinder. In the present invention, the integrated nut-piston assembly is directly attached to a single shank which can then be coupled to a shank on the gate, allowing the gate to be positioned. The use of electric screw drive actuators in combination may also reduce the need for redundant hydraulic systems, resulting in the elimination of 50% connectors, valves, piping, pumps, filters, etc., but still 100% redundant. An additional advantage is that the two drive systems are technically independent and therefore do not both fail due to the same component defect or failure point. These systems may also be used simultaneously if the conditions require a force that exceeds the force generated by the hydraulic actuator alone.

Because the nut and piston are integrated into a single unit and cannot be disengaged, the screw rotates whenever the nut moves, either by turning the screw via an electric motor or applying hydraulic fluid and pressure to one side of the piston-nut assembly to cause the nut to move. When the piston is hydraulically moved resulting in a back drive of the screw drive, the hydraulic pressure must overcome the load associated with the back drive of the screw and gearbox, and the electric motor must have the ability to disengage. Likewise, when using a screw and electric motor to move the actuator, the thrust output must overcome the losses associated with pushing hydraulic fluid out of the hydraulic volume and through the associated path of hydraulic tubing and valves.

One embodiment of the present invention utilizes a simplified hydraulic system that can be configured in a variety of ways to create redundant layers while having the ability to meet de-energizing stroke requirements. The ability to continue positioning the actuator without powering the electric motor is achieved by using a bank of hydraulic accumulators. The accumulator provides a means for storing electricity and can be introduced into the actuator in the event of a power failure of the motor.

The hydraulic system will be greatly simplified compared to conventional hydraulic power units. One method of charging or maintaining charging in a hydraulic accumulator may be to use an electric motor to drive a screw to push an integrated nut piston, thereby creating fluid flow and pressure to be directed to the accumulator. This can be accomplished while simultaneously positioning the fluid coking valves according to process requirements. The motor screw drive output must accommodate the additional load created when charging the accumulator and the load requirements of moving the gate on the spool valve.

To create an additional redundant layer, the hydraulic circuit includes a hydraulic pump that can be cycled on and off to recharge the accumulator when needed using an electric motor screw drive to move the piston through a backup method as described above. In a system thus constructed, there are three levels of redundancy. The first layer is the use of an electric motor screw to move the integrated nut/piston assembly. The second layer is the use of fluid power stored in an accumulator. The third level is to use the pump and the pressure and flow generated by it to move the system.

With respect to the hydraulic system, it will be greatly simplified compared to conventional hydraulic power units, and will not require numerous valves or redundant pumps and reservoirs. Thus, the simplified system may be very compact, self-contained, and positioned relatively close to the actuator and valve. This would be advantageous to reduce the losses associated with long hoses or pipes that need to extend from the hydraulic power unit to the actuators. The reduction in system size is also valuable to end users because the positioning of these valves in refineries is very limited and often blocks personnel exit paths and creates access problems for maintenance. Embodiments that use this integrated design and eliminate the need for redundant hydraulic systems provide important advantages of the system for fluid coking services.

Some embodiments of the present invention utilize an electric motor driven rolling element screw to address the requirement for continuous uninterrupted operation of fluid cracking and/or flexicoking control valves. By integrating the nut with the hydraulic piston, the desired upset condition operating requirements can be achieved, thereby reducing costs and complexity of conventional hydraulic systems. The system also reduces the complexity of the required controls of conventional hydraulic systems, thus reducing costs. The system has multiple layers of technically independent system redundancy that are required for a fluid cracking system and/or flexicoking. This ensures that in the case of a fluid cracking valve, it remains operable under all conditions. Equipment space on FCC and flexicoker is often challenging. The system minimizes the space requirements for installation in the FCC and flexicoker compared to conventional systems, thereby providing better accessibility for maintenance. Additional benefits may include improved personnel egress to allow personnel to safely exit the structure in an emergency.

Drawings

The objects and features of the present invention will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which:

FIG. 1 illustrates a perspective view of an embodiment combining electric and hydraulic linear actuators to provide, individually or collectively, a linear force output to a single stem connected to a linearly actuated valve;

FIG. 2 shows an elevational view of a fully integrated embodiment combining a conventional screw-driven linear actuator and a hydraulic actuator; and is

Fig. 3 shows an enlarged cross-sectional view of a hybrid electric/hydraulic linear actuator.

Detailed Description

A linear electric actuator system is presented that combines the features of an electric motor screw driven linear actuator and a hydraulic linear actuator. The benefit of combining the two types of linear actuators is to provide a measure of independent redundancy system for applications that require redundancy to prevent shutdowns and process interruptions.

In addition to the benefits of a truly independent redundant system, several new and novel control options can be implemented. By combining the unique and independent operating features available only with electric motor screw drive actuators with the unique and independent operating features available only with hydraulic linear actuators, new and novel control functions can be implemented.

There are two embodiments for combining electric and hydraulic actuators into one system that work together to create a redundant integrated system. The embodiment in fig. 1 depicts a combination of individual elements, including a hydraulic cylinder with a linear electric actuator (the linear electric actuator and the hydraulic cylinder are connected via a common mounting plate) and a linkage assembly tying each end of the actuation rod together.

The integrated embodiment shown in fig. 2 integrates electro-technology and hydraulic technology by designing a hydraulic piston that includes guides/bearings and seals to be physically integrated into and/or capture the nut of the electric actuator screw drive actuator. In this way, the hydraulic fluid and the drive screw will occupy the same space. This embodiment minimizes the points of failure in the system and minimizes the physical size of the system.

Referring now to the embodiment of fig. 1, there is depicted an embodiment having a hydraulic linear actuator 10 and an electric linear actuator 12, both the hydraulic linear actuator 10 and the electric linear actuator 12 being mounted to a bearing mounting guide frame assembly 14. Components such as the mounting plate 16, the bar linkage linear guide bearing 20, the linear guide bearing guide 21, the bar linkage 22, and the bar guide bearing 18 are all mounted to the frame assembly 14. The frame assembly 14 is comprised of end mounting plates attached by rails 24. Linear guide bearings 20 and linear guide bearing rails 21 are mounted to the rails. The rod guide bearing 18 is mounted into an end plate 16 (the end plate 16 is also part of the frame assembly 14). The rod end tie block 22 ties together a hydraulic actuator rod 26 and an electric actuator rod 28. The bar linkage 22 is guided by the linear guide 21 and the linear guide bearing 20. The hydraulic actuator rod 26 and the electric actuator rod 28 are connected to a rod linkage 22, which rod linkage 22 is also connected to a single centrally mounted rod 30 that provides a single linear output.

Actuation of one or both of the hydraulic actuator rod 26 or the electric actuator rod 28 will move the rod tie block 22, which then moves the single central rod 30 through the rod guide bearing 18. The rod guide bearing 18 provides low friction guidance for the single central rod 30 and reacts to applied forces that are not in the direction of travel of the single central rod 30. A single central rod 30 is attached to the linearly actuated valve.

A redundant system is achieved by connecting the extension/retraction rods 26, 28 together, or by designing the electrical and hydraulic actuators as a single unit that physically occupies the same space as in the other embodiments. The unit can be operated under a variety of conditions to take advantage of the unique control capabilities of both systems simultaneously.

In a second embodiment, the embodiment shown in fig. 2 utilizes a linear electric actuator system that combines the features of an electric motor screw driven linear actuator and a hydraulic linear actuator. The benefit of combining the two types of linear actuators is to provide a method for a redundant system independent for applications that require redundancy to prevent shutdowns and process interruptions.

In addition to the benefits of a truly independent redundant system, several new and novel control options can be implemented. By combining the unique and independent operating features that are available only with electric motor screw drive actuators with the unique and independent operating features that are available only with hydraulic linear actuators, new and novel control features can be implemented. In this embodiment, both technologies are integrated by designing a hydraulic piston that includes guides/bearings and seals to be physically integrated into and/or capture the nut of the electric actuator screw drive actuator. In this embodiment, the hydraulic fluid and the drive screw occupy the same space. This embodiment minimizes the points of failure and also minimizes the space, particularly the length of the system. The unit can also be operated under various conditions to take advantage of the unique control capabilities of both systems simultaneously.

When hydraulic fluid power is used to generate thrust to move the nut-piston assembly during extension or retraction of the rod, the thrust generated by the hydraulic pressure on the piston is allowed to passively back drive the screw and the powertrain. There is no torque applied via operation of the electric motor. The use of a high efficiency screw limits the force required to back drive the screw to a minimum.

When electric power is supplied to the electric motor to generate thrust in the extension/retraction rod, the hydraulic system is allowed to transfer hydraulic fluid from one side of the piston to the other with minimal losses. The loss of thrust due to pushing hydraulic fluid through the control valve is determined by the size of the control valve and the hydraulic lines. Alternatively, hydraulic pressure combined with the application of torque from the electric motor is applied to either side of the piston, matching the speed and direction of the drive screw nut to account for fluid losses (which would equal the losses in thrust generation). This would be useful in situations where maximum speed is required for movement of the extension/retraction lever.

Referring now to fig. 2, there is shown a fully integrated unit that combines a screw driven linear electric actuator with a hydraulic actuator. The electric motor 44 drives the gear reducer 46 through a shaft alignment coupling 48. The mount 50 creates a space between the electric motor 44 and the gear reducer 46 and the shaft connecting them. The first stage gear reducer 46 drives a drive belt/chain/gear 52 inside a gear housing 54. It will be appreciated that belts, chains or gears are used for this purpose. The belt 56 drives a system attached to the output shaft of the second stage gear set 59, which consists of a drive gear/pulley in a belt/chain assembly and a drive end of a screw 58. It should be appreciated that gears of varying sizes may be used to vary the speed and/or thrust required for each application. The combination of the gear sets 46, 52, 59 and the electric motor specifications define the speed and thrust of the screw/nut 60. Drive screw retention nut 62 captures drive screw 58 and is pre-tensioned to provide proper alignment/thrust bearing preload and to prevent fatigue of the screw end from changing in the direction of the applied force. The thrust bearing housing 64 and the drive screw thrust and alignment bearing set 66 maintain the drive screw 58 in alignment. The piston 69 is moved by hydraulic pressure to push or pull the actuator rod 76. Hydraulic fluid is provided through hydraulic fluid supply line 68. Surrounding the drive screw 58 is a piston/nut guide housing 70. This forms part of the pressure boundary for the hydraulic system and provides alignment of the piston/nut assembly so that it is concentric with the bearing housing 64 and the drive screw 58. The hydraulic fluid return line 72 allows hydraulic fluid to enter or exit the front (rod side) of the hydraulic chamber, which forms a rod side hydraulic volume. The rod guide seal assembly 74 provides guidance and acts as a bearing for the sliding rod. The assembly also provides a seal against the rod and front hydraulic volume. The actuator rod 76 is directly connected and sealed to the piston/nut carrier 78 and thus to the piston 69. The hollow portion of the rod 76 is exposed to hydraulic pressure only from the screw side of the piston 69. The hydraulic piston seals on the piston/nut carrier seal one side of the assembly in the housing from the other side.

This is done using a hollow push rod sealed at the ends of the U-shaped fork. The push tube is attached and sealed to the nut carrier/piston. The assembly 81 seals hydraulic fluid pressure from one side of the piston 69 to the other.

Referring now to fig. 3, a drive screw retaining ring 80 is shown, which drive screw retaining ring 80 captures and retains drive screw nut 69 in piston/rod assembly 81. The piston/nut wear guide 86 guides the piston/nut assembly 81. Hydraulic piston seals 88 separate the front or outside diameter rod side hydraulic volume from the rear or inside diameter rod hydraulic volume. A piston/nut wear guide 90 guides the piston/nut assembly 81.

The electric motor screw drive system passes the rotation and torque output from the electric motor 44 through the gear/transmission systems 52 and 46 and into the drive screw 58. Preventing the nut/piston assembly 81 from rotating. Because the main drive screw 58 is rotated and the nut 60 is not allowed to rotate, the nut 60 changes a linear position that coincides with the centerline of the screw 58 axis. The nut carriage/piston assembly 81 is connected to the rod 76 and can linearly translate the rod 76 when moved by an applied load. The thrust output is a function of the electric motor output torque, which subtracts inertial and frictional losses (fluid losses in the case of the present invention) in the system.

Conventional hydraulic systems having redundant designs utilize hydraulic power units with redundant pump and valve control systems to minimize the effects of individual component failures. The space requirements, complexity and cost of such systems are important. In the present invention, the redundancy created by multiplying these components can be recreated in a space-saving system using an efficient electrically operated screw driven linear actuator. In addition, the redundancy of the system utilizes two different techniques, which prevent multiplication of the vulnerabilities inherent in one system, thus creating a truly independent redundant system.

Hybrid electro-hydraulic actuator systems utilize typical hydraulic system valves to control a conventional hydraulic cylinder through additional valves to allow the cylinder to passively move hydraulic fluid from one side of a piston to the other side of the cylinder or combined electro-hydraulic cylinders. This allows the piston to be moved independently of the hydraulic system with a torque input from the electric motor drive system to the screw/driver.

When hydraulic fluid power is used to generate thrust to move nut-piston assembly 81 during extension or retraction of rod 76, the thrust generated by hydraulic pressure on piston 69 is allowed to passively back drive screw 58 and the powertrain. There is no torque applied via operation of the electric motor. The use of a high efficiency screw 58 limits the force required to back drive the screw 58 to a minimum.

When electrical power is supplied to the electric motor 44 to generate thrust in the extension/retraction rod 76, the hydraulic system is allowed to transfer hydraulic fluid from one side of the piston to the other with minimal losses. The loss of thrust due to pushing hydraulic fluid through the control valve will be determined by the size of the control valve and the hydraulic lines.

Alternatively, hydraulic pressure combined with the application of torque from the electric motor 44 may be applied to either side of the piston 69 to match the speed and direction of the drive screw nut 60 to account for fluid losses (which would equal the losses in thrust generation). This would be useful in situations where maximum speed is required for movement of the extension/retraction lever 76.

This embodiment combines the functionality of both an electric screw driven linear actuator and a conventional hydraulic linear actuator system. Because the system is designed to operate as a linked-together independent electric actuator or independent hydraulic actuator system, control of the combined system under basic operation is not affected by failure of the other systems. The functionality of the combined system will be managed by a high level control system, such as a microcontroller or PLC, managing the logic required for operation. The number of inputs is numerous and includes redundant position encoders, pressure sensors, servo and control valves, VFDs, and soft starters. Possible locations include: electric operation of the hydraulic system bypass-retract; electric operation of the hydraulic system bypass-extension; hydraulic system operation of the passive back-drive screw-extension; and hydraulic system operation of the passive back-drive screw-retraction. Obviously, all positions in between these positions are also available. It is also possible to obtain: hydraulic deceleration and position assisted electric operation; hydraulically hard stopping the electric operation of the final positioning; hydraulic operation of electric final positioning; and electric operation of the accumulator without pump replacement. The accumulator is used to store pressurized hydraulic fluid that can be used to hydraulically actuate the lever 76 even when the hydraulic system fails. The accumulator may also provide hydraulic assistance for electrical actuation of the rod 76.

In the foregoing detailed description, various features of the disclosure are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of the present disclosure should not be interpreted as reflecting an intention that: the claimed disclosure requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. It is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present disclosure. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of the present disclosure, and the appended claims are intended to cover such modifications and arrangements. Thus, while the present disclosure has been illustrated in the accompanying drawings and described above with particularity and detail, it will be apparent to those skilled in the art that numerous modifications, including, but not limited to, variations in size, materials, shape, form, function and manner of operation, assembly and use may be made without departing from the spirit and scope of the disclosure.