Patent Description:
The present invention relates generally to fluid systems. More particularly, the present invention relates to accumulators used for fluid storage in open and closed-loop fluid systems such as, e.g., hydraulic systems.

An accumulator for an incompressible fluid, such as a hydraulic fluid, is a pressure storage reservoir in which the incompressible fluid is held under pressure, i.e., "charged," by a force from, e.g., a spring or compressed gas. Accumulators inject stored energy (e.g., in the form of pressurized fluid) back into the fluid system when needed. Accumulators are in widespread use in most sectors of hydraulics, machinery, and automations. They are versatile, improve machines' comfort, protect hydraulic systems and are used to increase the energy efficiency of hydraulic systems. For example, using an accumulator as an energy storage device effectively reduces the required flow rate capacity of a fluid pump, which results in a reduction of the installed power. When charged, an accumulator allows for instant and/or repetitive operations as required (braking, opening of a door, or some other repetitive operation based on the application).

In some fluid system the accumulator helps dampen pulsations and reduces noise in the fluid system, which are caused by, e.g., the pulsations of a pump. Due to the low inertia of an typical accumulator, e.g. a bladder-type accumulator, the accumulator can quickly adjust for these pressure changes and improve the precision of operation and reduce the noise level of the system. In closed-loop systems, an accumulator can store/release fluid to account for pressure differences caused by thermal variation in the closed circuit. In high-volume flow systems, an accumulator that is correctly sized and located within the system provides protection from surge and water hammer damage by transforming the pressure wave oscillations into liquid mass oscillations, which are easily absorbed by the accumulator to bring the pressure peak level back to an acceptable level. On industrial machines such as maintenance machinery and transport platforms, an accumulator that is connected to the suspension chamber acts as an adjustable shock absorber. In addition to the above, depending on the application, accumulators can provide suction flow stabilization, volume and leakage adjustment, weight equalization, energy recovery and recuperation.

Some common type of accumulators are bladder-type accumulators, diaphragm-type accumulators and piston-type accumulators. Bladder-type accumulators include a shell and a bladder disposed inside the shell. The bladder is charged with a compressed gas such as nitrogen, air or another gas. When the pressure in the fluid system is higher than the pressure in the bladder-type accumulator, fluid is forced into the accumulator, which compresses the bladder until the system pressure equals the pressure of the nitrogen in the bladder. When the system pressure drops below that of the compressed gas, the compressed gas expands and forces the stored fluid into the fluid circuit until the pressures equalize one again. Diaphragm-type accumulators use a flexible member to separate two chambers of the accumulator. One chamber is filled with compressed gas and the other is connected to the fluid circuit. Similar to bladder-type accumulators, differences in pressure between the compressed gas and the system fluid will cause the fluid to enter or exit the accumulator. Finally, a third type of accumulator, the piston-type of accumulator, uses a rigid piston to separate two chambers of the accumulator. Similar to the bladder-type accumulator, one chamber is filled with compressed gas and the other is connected to a fluid circuit. The piston is designed to slide along the wall of the accumulator when there is a pressure difference between the compressed gas and the fluid circuit. By sliding, the piston allows fluid to enter and exit the accumulator.

The accumulators discussed above have various safety and maintenance issues.

Diaphragm and bladder type accumulators experience wear and tear due to the mechanical cycling. In addition to the stresses caused by mechanical cycling, the diaphragm also experiences thermal stresses due to temperature changes from the gas being compressed and expanded during operation. In addition, the gas in the above accumulators are always under pressure, which can mean that some or all of the hydraulic system equipment is always under pressure. That is, the accumulator and system can have trapped pressure even when no operation is taking place. Thus, the accumulators and the system equipment must be configured to withstand the trapped pressure on a <NUM>-hour basis and not just when the equipment is being operated. This means that, for safety reasons, the wall thicknesses of the accumulators and the system equipment will be greater than if the pressure in the accumulators was only applied during operation. Further, because the gas is always under pressure in the above accumulators, the accumulators must be specifically pre-configured to each application. Accordingly, the same accumulator configuration cannot be used for a variety of pressure and volume flow conditions. Indeed, the accumulators cannot even adjust to any significant changes in the same application. For example, changes in the volume, pressure and/or response times in the system due to, e.g., equipment changes in the system due to, e.g., upgrades.

Further limitations and disadvantages of conventional, traditional, and proposed approaches will become apparent to one skilled in the art, through comparison of such approaches with embodiments of the present invention as set forth in the remainder of the present disclosure with reference to the drawings. <CIT> discloses a fluid system according to the preamble of claim <NUM> and claim <NUM>.

The summary of the invention is provided as a general introduction to some embodiments of the invention, and is not intended to be limiting to any particular fluid system.

It is to be understood that various features and configurations of features described in the Summary can be combined in any suitable way to form any number of embodiments of the invention as long as they remain within the scope of the claims.

Some additional example embodiments including variations and alternative configurations are provided herein.

As used herein, "fluid" means an incompressible liquid or a substantially incompressible liquid, e.g., an incompressible liquid having some entrained gas but not enough to substantially affect the incompressible nature of the fluid mixture.

The invention provides a fluid system, comprising:.

Optionally, the motor is disposed in the interior volume between the first interior surface of the shell and the piston-plate.

Optionally, the piston-plate is part of an outer casing of the motor, the piston-plate disposed on a plane that is perpendicular to the longitudinal axis of the shell.

Optionally, the piston plate is a separate disk that is disposed adjacent to the motor casing (<NUM>) and coupled to either the inner motor casing (70a) or the outer motor casing (70b).

Optionally, the interface between the shaft of the motor and the accumulator shaft prevents rotation movement of the motor shaft relative to the accumulator shaft and allows the piston-plate to linearly travel along the accumulator shaft.

The invention further provides a fluid system, comprising:.

Optionally, an interface between the inner surface of the shell and the outer radial surface of the piston-plate prevents rotation movement of the piston-plate relative to the shell and allows the piston-plate to linearly travel along the accumulator shaft.

Optionally, the motor is a transverse flux motor.

Optionally, the motor is a bidirectional, variable speed motor.

Optionally, the motor is a bidirectional, fixed speed motor.

Optionally, the motor is a servomotor that provides precise control of at least one of a position and speed of the motor.

Optionally, the motor is a low-speed, high-torque motor that operates in a range of <NUM> rpm to <NUM> rpm.

Optionally, the fluid-driven actuator is a fluid-driven cylinder.

Optionally, the fluid is hydraulic fluid.

The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate exemplary embodiments of the invention, and, together with the general description given above and the detailed description given below, serve to explain the features of the preferred embodiments of the invention.

As seen in <FIG>, an accumulator <NUM> includes a shell <NUM> that defines an interior volume <NUM>. In the illustrated embodiment, the shell <NUM> includes a main body <NUM> and endplates <NUM> and <NUM>, which are attached to the main body <NUM>. Preferably, the main body <NUM> is a hollow cylinder. However the main body can have other shapes, such as, e.g., a rectangular shape. Preferably, the endplate <NUM> includes ports 25a, 25b to connect to a fluid system. Although two ports are shown in <FIG>, in some embodiments, the accumulator <NUM> can include one port or more than two ports. In addition, the port or ports can be in the main body instead of the endplates <NUM>, <NUM>. Preferably, as seen in <FIG>, each of the endplates <NUM>, <NUM> has a threaded portion 20a, 22a, respectively, to receive sections 15a of the main body <NUM>. Sections 15a have threads corresponding to threaded portions 20a, 22a such that the threaded interfaces between the main body <NUM> and each of the endplates <NUM>, <NUM> forms a tight, secure connection. Of course, other means to attach the main body <NUM> to the endplates <NUM>, <NUM> can be used such a bolted connection, a welded connection or some other known means that will secure the main body <NUM> to the endplates <NUM>, <NUM>. Although not shown, gaskets, O-rings or some other sealing means can be used at the interface between the main body <NUM> and endplates <NUM>, <NUM> to ensure that fluid in the interior volume18 of the shell <NUM> will not leak outside the accumulator <NUM>. In high-pressure systems, a seal-weld on the exterior of the main body <NUM> at the interface to endplate <NUM> can be used to ensure that the accumulator is properly sealed. In some embodiments, the interface at endplate <NUM> need not be sealed or need to have a tight seal because the chamber 19b will remain unpressurized. In some embodiments, the main body <NUM> and one of the endplates <NUM>, <NUM> can form one integral unit. For example, the main body <NUM> and endplate <NUM> can be machined or forged as a single piece. Of course, although endplates <NUM>, <NUM> are shown as disks, the endplate can be any appropriate shape such as, e.g., a dome.

An accumulator shaft <NUM> is disposed in the interior volume <NUM> of the main body <NUM> along the longitudinal axis A-A of the accumulator <NUM>. In the exemplary embodiment, axis A-A is the central axis. Preferably, the accumulator shaft <NUM> is attached to one interior surface of the shell <NUM> and extends at least partially across the interior volume <NUM> along the longitudinal central axis A-A. In some embodiments, the accumulator shaft <NUM> extends the full length of the interior volume <NUM>. Preferably, the accumulator shaft <NUM> is fixedly attached to each endplate <NUM>, <NUM>. For example, the accumulator shaft <NUM> can be attached to the endplates <NUM>, <NUM> using endplate covers <NUM>, <NUM>, respectively. Bolts, screws or other known fastening means can be used to attach the accumulator shaft <NUM> to the endplate covers <NUM>, <NUM>. The endplate covers <NUM>, <NUM> can also to serve to seal the interior volume <NUM> from the outside. Although not shown, gaskets, O-rings or other known sealing means can be used between the endplate covers <NUM>, <NUM> and the respective endplate <NUM>, <NUM> to provide the sealing. Of course, the accumulator shaft <NUM> can be attached to the one or both of the endplates <NUM>, <NUM> using other means of attachment such as a threaded connection. In some embodiments, the accumulator shaft <NUM> does not penetrate or only partially penetrates into one or both of the endplates <NUM>, <NUM>. In such cases, the endplate covers <NUM>, <NUM> may not be needed.

A piston-plate <NUM> is disposed on the accumulator shaft <NUM> such that the piston-plate <NUM> travels along the accumulator shaft <NUM>. The piston-plate <NUM> separates the interior volume <NUM> into two chambers 19a, 19b. The piston-plate <NUM> can be made of any appropriate material for the fluid application. For example, in hydraulic fluid the piston-plate can be made of a metal such as, e.g., steel and alloys thereof and aluminum and alloys thereof, to name just a few. In other applications, e.g., applications that include reactive chemicals, the piston-plate <NUM> can be coated with an appropriate non-reactive material and/or made of, e.g., a plastic or a ceramic, to name just a few. In the exemplary embodiment of <FIG>, a motor <NUM>, which has a central passageway <NUM> (see <FIG>), is disposed on the accumulator shaft <NUM> between the piston-plate <NUM> and an inner surface of the shell <NUM>, e.g., endplate <NUM>. The motor <NUM> is coupled to the piston-plate <NUM> such that rotational movement of the motor <NUM> translates to a corresponding linear movement of the piston-plate <NUM> along the central axis A-A.

As seen in <FIG>, the piston-plate <NUM>, with motor <NUM>, acts similar to a piston found in traditional piston-type accumulators. However, while the piston-plate <NUM> acts similar to a traditional piston, those skilled in the art, after reading the present specification, will understand exemplary embodiments of the present disclosure provide advantages not found in traditional piston-type accumulators. For example, in exemplary embodiments of the present disclosure, the motor <NUM> removes the need for an energy storage device such as a diaphragm or a bladder with compressed gas, which eliminates maintenance issues related to the diaphragm or bladder. In addition, the motor <NUM> only exerts pressure on the fluid system when the system is in operation. Thus, because the pressure will be removed after operation, the accumulator <NUM> and the system will not constantly be under pressure. Accordingly, the accumulator <NUM> and equipment can be lighter (e.g., due to the accumulator having thinner walls) and still maintain a comfortable safety factor. In addition, because an "intelligent" control system can be configured to control motor <NUM> of accumulator <NUM>, changes in the system conditions such as pressure, volume flow, response times or some other change due to, e.g., upgrades to equipment or for some other reason can be easily accounted for by adjustment to, e.g., the algorithms that control motor <NUM>. Further, unlike the prior art accumulators that are configured for specific applications, the same accumulator configuration can be used in a variety of applications with only the control philosophy for motor <NUM> being application specific. This is possible because the controller can be easily reprogrammed with customized algorithms for the various applications.

As discussed above, motor <NUM> is configured such that rotational movement of the motor <NUM> translates to a corresponding linear movement of the piston-plate <NUM> along the accumulator shaft <NUM>. Preferably, the piston-plate <NUM> is directly coupled to motor <NUM> and is, e.g., a part of the casing (or housing) for motor <NUM>. Preferably, the central passageway <NUM>, which is disposed along, e.g., the central axis of the motor <NUM>, receives the accumulator shaft <NUM> such that the motor <NUM> and piston-plate <NUM> travel along the accumulator shaft <NUM>. Preferably, as seen in <FIG> and explained further below, the piston-plate <NUM> is a part of the casing of the motor <NUM>. The motor <NUM> is coupled to the accumulator shaft <NUM> and rotates the accumulator shaft <NUM> to linearly move piston-plate <NUM>. Of course, other coupling arrangements between the motor <NUM> and piston-plate <NUM> can be used so long as rotational movement of the motor <NUM> translates to linear movement of the piston-plate <NUM>. In the embodiment of <FIG>, which is not covered by the claims, the piston-plate <NUM> and the motor <NUM> can be separate devices that are coupled together via the accumulator shaft <NUM> or through some other means. In such exemplary embodiments where the piston-plate <NUM> is not a part of motor <NUM>, the motor <NUM> need not move linearly with the piston-plate <NUM>. For example, as seen in <FIG>, the motor <NUM> can be disposed in an appropriate location such as, e.g., at endplate <NUM> (or at endplate <NUM> - not shown), or as seen in <FIG>, the motor <NUM> can be disposed outside the shell <NUM>. The motor <NUM> in the exemplary embodiments of <FIG> can remain fixed or stationary.

Returning to the exemplary embodiment of <FIG> and <FIG>, preferably, the motor <NUM> includes a motor casing <NUM> that surrounds and protects the stator <NUM> and rotor <NUM>. In some embodiments, the casing <NUM> has inner motor casings 50a and 70a, outer motor casings 50b and 70b and outer radial casing 50c. The outer motor casings 50b and 70b and outer radial casing 50c can be an integral unit in some embodiments. Preferably, the inner motor casing 70a and the outer motor casing 70b, along with bearing <NUM>, form the piston-plate <NUM>. Of course, other arrangements can be used to form piston-plate <NUM>. For example, the piston-plate <NUM> can be a separate disk that is disposed adjacent to the motor casing <NUM> and coupled to either the inner motor casing 70a or the outer motor casing 70b.

Preferably, the motor <NUM> has an outer-rotor configuration, which means that the outside of the motor rotates and the center of the motor is stationary. In contrast, in an inner-rotor motor configuration, the rotor is attached to a central motor shaft that rotates. As seen in <FIG>, the stator <NUM> is radially disposed between the motor shaft <NUM> and the rotor <NUM>. The motor shaft <NUM> is hollow and the interior wall <NUM> of the motor shaft <NUM> defines the central passageway <NUM>. The rotor <NUM> is disposed radially outward of the stator <NUM> and surrounds the stator <NUM>. The rotor <NUM> is coupled to the stator <NUM> via bearings <NUM>, <NUM> such that the rotor <NUM> can freely rotate around stator <NUM>. For example, in <FIG>, the stator <NUM> is fixedly attached to inner motor casings 50a and 70a which are coupled to bearings <NUM> and <NUM> respectively. The rotor <NUM> is fixedly attached to the outer motor casings 50b and 70b, which are coupled to bearings <NUM> and <NUM>, and outer radial casing 50c. The outer motor casings 50b and 70b and outer radial casing 50c are fixedly attached to the rotor <NUM> such that the outer motor casings 50b and 70b and outer radial casing 50c rotate with the rotor <NUM>. Although the bearings <NUM> and <NUM> are shown attached to the motor casing <NUM>, in other embodiments, the bearings can directly connect the stator portion to the rotor portion.

Preferably, the diameter D of piston-plate <NUM>, which includes the motor casings 70a and 70b, is substantially the same as the interior diameter d of the shell <NUM> (see <FIG>). In the exemplary embodiment of Figure, because the piston-plate <NUM> is part of the motor, the diameter D of the motor <NUM> will also be substantially the same as the interior diameter d of the shell <NUM>. Preferably, the diameter D of the motor <NUM> and thus the piston-plate <NUM> is in a range of <NUM> inches (<NUM>) to <NUM> inches (<NUM>). Preferably, the outer radial motor casing 50c includes a threaded portion <NUM> along at least a portion of the outer radial surface <NUM> of the outer radial motor casing 50c. In some embodiments, the threaded portion can be the full-length of the outer radial surface <NUM>, including the outer radial surface of the piston-plate <NUM>. In other exemplary embodiments, only the outer radial surface of the piston-plate <NUM> is threaded. The threaded portion <NUM> engages with matching threads <NUM> disposed on the interior of shell <NUM>. Preferably, the thread pitch is very fine such that a full rotation of the motor <NUM> translates to only a small linear movement along the accumulator shaft <NUM>. For example, the thread pitch can be in a range from <NUM> to <NUM>. In some embodiments, the thread size is M80. When assembled, the interface between the threaded portions of the motor <NUM> and/or piston-plate <NUM> and the shell <NUM> have a small tolerance such that it forms a seal to prevent or substantially prevent fluid from passing between the motor <NUM>/piston-plate <NUM> and shell <NUM>. However, the tolerances are not so tight as to interfere with the rotational movement of the motor <NUM>/piston-plate <NUM>.

Preferably, the motor <NUM> is bidirectional, i.e., the motor can rotate in either direction depending on operational needs. In some embodiments, the motor <NUM> is a low-speed, high-torque motor. For example, the motor can be a transverse flux motor that provides high torque density, e.g., such as that disclosed in International Patent Application Publication No. <CIT>.

In some exemplary embodiments, the motor <NUM> can be a variable speed and/or a variable torque motor in which the speed of the rotor is varied to create various volume flows and pressures. In some embodiments, the motor is a fixed-speed motor. In some embodiments, the motor is a low-speed, high-torque motor. Whether fixed-speed or variable speed, preferably, the motor operates in a range of <NUM> revolutions per minute (rpm) to <NUM> rpm. Preferably, in some embodiments the motor <NUM> is fixed-speed and approximately <NUM> rpm. In other embodiments, the speed is approximately <NUM> rpm and in still other embodiments, the speed is approximately <NUM>. Whether fixed speed or variable, preferably, the motor has a torque in a range of <NUM> N-m to <NUM> N-m. In some embodiments, the torque is <NUM> N-m at <NUM> rpm and in other embodiments, the torque is <NUM> N-m at <NUM> rpm. Preferably, a diameter of the motor <NUM> is in a range of <NUM> inches (<NUM>) to <NUM> inches (<NUM>), and a length of the motor <NUM> is in a range of <NUM> inches (<NUM>) to <NUM> inches (<NUM>). In some embodiments, any of the motors described above can be configured as a servomotor to allow for precise control of the position and/or speed of the motor <NUM>. Precision control of servomotors is known in the art and thus for brevity, will not be further discussed except as necessary to describe the exemplary embodiments of the present disclosure.

Preferably, the interior wall <NUM> of motor shaft <NUM> includes indents and/or protrusions that engage with corresponding protrusions/indents in the accumulator shaft <NUM> such that an interlocking arrangement is formed to prevent the shaft <NUM> and thus the stator <NUM> from rotating relative to the accumulator shaft <NUM>. That is, in this exemplary embodiment, the stator <NUM> is fixed to the accumulator shaft <NUM> in the rotational direction. However, the motor <NUM>/piston-plate <NUM> is free to linearly travel along the accumulator shaft <NUM> in the longitudinal direction. For example, <FIG> illustrates a cross-sectional view of an interface between an exemplary motor shaft 48A and an exemplary accumulator shaft 30A. As seen in <FIG>, the interior wall 49A of motor shaft 48A has indents <NUM> in the form of, e.g., grooves. The indents <NUM> are spaced periodically around the surface of the wall 49A and extend the entire length of the motor shaft 48A. The exterior surface of accumulator shaft 30A has protrusions <NUM> that correspond to the indents <NUM> on the motor shaft 48A. As illustrated in <FIG>, the protrusions <NUM> can be in the form of, e.g., fins. The protrusions <NUM> engage with indents <NUM> on the motor shaft 48A to from an interlocking arrangement to prevent the stator <NUM> from rotating relative to the accumulator shaft 30A.

In some embodiments, as seen in <FIG>, the interior wall 49B of motor shaft 48B has protrusions <NUM> in the form of, e.g., fins. The protrusions are spaced periodically around the surface of the wall 49B and can extend the entire length or a portion of the length of the motor shaft 48B. The exterior surface of accumulator shaft 30B has indents <NUM>, e.g., grooves, that correspond to the protrusions <NUM> of the motor shaft 48A. The indents <NUM> can extend the entire length of the accumulator shaft 30B or at least the portion that the motor <NUM> needs to travel. The indents <NUM> engage with protrusions <NUM> on the motor shaft 48B to from an interlocking arrangement to prevent the stator <NUM> from rotating relative to the accumulator shaft 30B. In some embodiments, the motor shaft and the accumulator shaft have a mixture of corresponding indents and protrusions.

In some embodiments, the protrusions on the motor shaft <NUM> and accumulator shaft <NUM> run the entire length or only a part of the length of the respective shafts without any breaks. For example, as shown in <FIG>, the protrusions <NUM>' on accumulator shaft <NUM>' run the entire length or nearly the entire length of the accumulator shaft <NUM>'. In some embodiments, the protrusions can be segmented along the length of the shaft. For example, in <FIG>, the protrusions <NUM>" are in segments along the length of the accumulator shaft <NUM>". Of course, if the motor shaft <NUM> has the protrusions, then they can be similarly arranged on the interior of the motor shaft in a manner analogous to that shown in <FIG>. The size, number and shape of the indents/protrusions in the above embodiments can vary so long as the motor <NUM> can slide along the accumulator shaft and the shafts form an interlocking arrangement to prevent rotational movement between the two shafts. Of course, the size, number and shape of the indents/protrusions should also be such that the interlocking arrangement and/or the shafts can withstand the rotational stresses of the motor <NUM>.

In some embodiments, the length of interior volume <NUM> is equal to or greater than the width or diameter of the interior volume <NUM>. In other embodiments the length of interior volume <NUM> is less than the width or diameter of the interior volume <NUM>. Preferably, a length to width (diameter) ratio of the interior volume <NUM> of the accumulator <NUM> is in a range of <NUM> to <NUM>. Preferably, the interior volume has a length in a range of <NUM> inches (<NUM>) to <NUM> inches (<NUM>) and a diameter in a range of <NUM> inches (<NUM>) to <NUM> inches (<NUM>). Preferably, the maximum volume capacity of chamber 19a of the accumulator <NUM> is in a range of <NUM> gallons (<NUM>) to <NUM> gallons (<NUM>). Preferably, the diameter of the accumulator shaft <NUM> is in a range of <NUM> inches (<NUM>) to <NUM> inches. (<NUM>) Of course, the above dimensions of the accumulator <NUM> are exemplary and can vary from the above ranges depending on the application.

As discussed above, the motor <NUM>/piston-plate <NUM> separates the interior volume <NUM> into two chambers 19a, 19b. Chamber 19a is in fluid communication with ports 25a and 25b. When the accumulator <NUM> is installed in a fluid system (e.g., see <FIG>), the chamber 19a is in fluid communication with the fluid system via ports 25a and 25b. Chamber 19b is isolated from the fluid system by the motor <NUM>/piston-plate <NUM>. As discussed above, tight tolerances between the motor shaft <NUM> and accumulator shaft <NUM> and between the motor threads <NUM> (and/or threads of piston-plate <NUM>) and shell threads <NUM> provide a sufficient seal so that fluid, e.g., hydraulic fluid, does not leak into chamber 19b. However, chamber 19b can include a drain (not shown) to carry away any fluid that enters chamber 19b. In some embodiments, the outer circumference of the outer radial casing 50c and/or piston-plate <NUM> can include a sealing ring strip <NUM> made of a material such as, e.g., Teflon, polyurethane, nitrile rubber, fluoroelastomer-viton, EPDM rubber, silicon rubber, proprietary filled TFE, aluminum and bronze, that slides or rotates against the shell <NUM> (depending on the type of interface) to help seal the threads and prevent fluid from entering the chamber 19b, i.e., to keep the fluid contained in chamber 19a. Preferably, a sealing ring strip <NUM> is disposed on at least the side adjacent to chamber 19a. The sealing ring strip <NUM> can be attached to the motor casing <NUM> using known means such that the ring strip is secure during operation. Preferably, as seen in <FIG>, a sealing ring strip <NUM> is disposed on both sides of the motor <NUM>. Including a sealing ring strip <NUM> on the side adjacent to chamber 19b aids in preventing air, dirt and other contaminates from entering chamber 19a and the hydraulic fluid as the motor <NUM> travels along accumulator shaft <NUM>. In addition, motor shaft <NUM> and/or accumulator shaft <NUM> can be coated with a material such as, e.g., Teflon, silicon and ceramic, to help seal the shaft area to prevent fluid from entering the chamber 19b, i.e., to keep the fluid contained in chamber 19a, to help in keeping air, dirt and other contaminants from entering the chamber 19a, and to help minimize the sliding friction between the motor shaft <NUM> and the accumulator shaft <NUM>. In some embodiments all or part of the motor shaft <NUM> can be made of a material such as, e.g., Teflon, polyurethane, nitrile rubber, fluoroelastomer-viton, EPDM rubber, silicon rubber, proprietary filled TFE, aluminum and bronze to help seal the shaft and minimize the sliding friction.

Unlike traditional accumulators, in some embodiments of the present disclosure, the chamber 19b of the accumulator <NUM> does not have stored energy. That is, the chamber 19b does not include compressed gas, a spring or another energy storage device. Instead, when it is determined that the fluid system needs additional energy, i.e., needs additional fluid, the motor <NUM> moves the piston-plate <NUM> to increase the pressure in the system by decreasing the volume of chamber 19a. Conversely, when it is determined that the fluid system needs less energy, i.e., the accumulator needs to receive excess fluid from the system, the motor <NUM> moves the piston-plate <NUM> to decrease the pressure in the system by increasing the volume of chamber 19a. In exemplary embodiments of the disclosure, the accumulator <NUM> can provide pressures in the range of <NUM> psi (<NUM> MPa) to <NUM> psi (<NUM> MPa) and maximum flow rates in a range of <NUM> gpm (<NUM> lpm) to <NUM> gpm (<NUM> lpm), depending on the application. In addition, depending on the application, the volume of the accumulator can be in a range from <NUM> gallon (<NUM>) to <NUM> gallons (<NUM>). Because the motor <NUM> controls the volume of chamber 19a to provide fluid to or releases fluid from the system as needed, stored energy, e.g., in the form of compressed gas and springs are not needed in some embodiments. In some exemplary embodiments, however, chamber 19b can have a stored energy, e.g., compressed gas in a bladder or diaphragm, a spring or another sorted energy device in order to aid the motor <NUM> when it is overcoming the system pressure in providing fluid to the system. Such a configuration can help in limiting the size of the motor in very high-pressure systems while retaining some of the advantages of a motor-operated accumulator.

In the above exemplary embodiments, the motor <NUM> has an outer-rotor configuration with a threaded interface between the motor and shell. However, in other exemplary embodiments, the motor can have an inner-rotor configuration and the motor shaft can be threaded. The threads on the motor shaft interface to matching threads on the accumulator shaft, which is fixedly attached to the shell. In this embodiment, as the motor rotates, the motor casing and piston-plate are configured to slide along the interface with the shell. Similar to the motor shaft <NUM> and accumulator shaft <NUM> discussed above, the motor casing and/or piston-plate can have indents and/or protrusion that interface with corresponding protrusions and/or indents on the accumulator shell to achieve the sliding interface. The piston-plate/motor casing-shell interface provides an interlock to prevent rotational movement of the motor casing relative to the shell. However, the interface still allows for linear movement in the longitudinal direction of the accumulator. Thus, when the motor rotates, the motor and piston-plate will travel along the accumulator shaft in both directions, depending on the direction of rotation of the motor.

In still other embodiments not covered by the claims, the shaft of an inner-rotor motor is coupled to the accumulator shaft, which is threaded and can rotate. The motor can be disposed outside the accumulator or even inside the accumulator. If inside the accumulator, the motor can be in either chamber of the accumulator and, in some embodiments, can act as an endplate. In exemplary embodiments, the threaded accumulator shaft can receive a piston-plate that is separate from the motor. The piston-plate includes a hub that has corresponding threads to interface with the threaded shaft. The outer circumference of the piston-plate, i.e., the interface to the shell, is configured to slide along the shell. Similar to the embodiments discussed above, the outer circumference of the piston-plate can have indents and/or protrusion that interface with corresponding protrusions and/or indents on the accumulator shell. The piston-plate-shell interface provides an interlock to prevent rotational movement of the piston-plate relative to the shell. However, the interface still allows for linear movement of the piston-plate in the longitudinal direction of the accumulator. Thus, when the motor rotates the accumulator shaft, the piston will travel along the accumulator shaft in both directions, depending on the direction of rotation of the motor. Of course, other coupling arrangements can be used between the motor and piston-plate so long as rotation of the motor translates to a corresponding linear movement of the piston-plate along the central axis A-A.

In the above embodiments, motor <NUM> is described as an electric motor. However, the motor can be another type of motor such as, e.g., a hydraulic motor or another type of fluid-driven motor.

<FIG> illustrates an exemplary embodiment of a fluid system. For purposes of brevity, the fluid system will be described in terms of an exemplary closed-loop hydraulic system application. However, those skilled in the art will understand that the concepts and features described below are also applicable to systems that pump other (non-hydraulic) types of fluids and/or to open-loop systems.

The hydraulic system <NUM> includes a hydraulic pump <NUM> providing hydraulic fluid to a hydraulic actuator, which is hydraulic cylinder <NUM> in this embodiment. However, those skilled in the art will understand that the actuator can be a hydraulic motor or another type of fluid-driven actuator that performs work on an external load. The hydraulic system <NUM> also includes valve assemblies <NUM> and <NUM>, which can be proportional control valves, lock valves or another type of valve appropriate for the intended application. In some embodiments, the system <NUM> can be configured to include only one of the valve assemblies <NUM> and <NUM>. The hydraulic system <NUM> can include a motor-driven accumulator <NUM>, which can be any of the exemplary embodiments discussed above. A controller <NUM> controls the flow and/or pressure in the system. A user can control the system via user interface <NUM>. The valve assembly <NUM> is disposed between port B of the hydraulic pump <NUM> and port B of the hydraulic cylinder <NUM>, i.e., the valve assembly <NUM> is in fluid communication with port B of the hydraulic pump <NUM> and port B of the hydraulic cylinder <NUM>. The valve assembly <NUM> is disposed between port A of the hydraulic pump <NUM> and port A of the hydraulic cylinder <NUM>, i.e., the control valve assembly <NUM> is in fluid communication with port A of the hydraulic pump <NUM> and port A of the hydraulic cylinder <NUM>. The accumulator <NUM> is connected to the system <NUM> between the port B of the pump <NUM> and valve assembly <NUM>. However, in some embodiments, the accumulator <NUM> can also be located between port A of the pump <NUM> and valve assembly <NUM> or in another appropriate location in the system <NUM>.

In some embodiments, the system can have two or more accumulators depending on the needs of the system. The system <NUM> can also have instrumentation sensors located throughout the system. For example, as shown in <FIG>, sensor assemblies <NUM>-<NUM> are located before and after each valve assembly <NUM>, <NUM>. However, the sensor assemblies are not limited to these locations and other locations can be used. Each of the sensor assemblies <NUM>-<NUM> can have a flow sensor, a temperature sensor and/or a pressure sensor.

In some exemplary embodiments, the pump <NUM> is a variable speed, variable torque pump. In other embodiments, the hydraulic pump <NUM> is a fixed-speed pump. In some embodiments, the hydraulic pump <NUM> is bi-directional. The pump <NUM> can include a pump control circuit <NUM>, which can include the drive control for the prime mover of the pump, e.g., electric motor, a hydraulic motor or another type of motor depending on the type of pump. The pump <NUM> is controlled by the controller <NUM> via the pump control circuit <NUM>. In some embodiments, the controller <NUM> is configured to control the speed and/or torque of the pump <NUM> in order to control the flow and/or pressure in the system <NUM>.

The exemplary embodiment of <FIG> includes two valve assemblies <NUM>, <NUM>. Each valve assembly <NUM>, <NUM> includes a valve <NUM>, <NUM>, respectively. The valves <NUM>, <NUM> can be control valves, shut-off valves or some other type of valve that is appropriate for the system application. The valve assemblies <NUM>, <NUM> also include valve control circuits <NUM>, <NUM>, respectively, that are appropriate for the type of valve. For example, if the valves <NUM>, <NUM> are control valves, the control circuits <NUM>, <NUM> can operate the valves <NUM>, <NUM> anywhere between <NUM>% and <NUM>% open. If the valves <NUM>, <NUM> are shut-off valves, the control circuits <NUM>, <NUM> can provide open and close command to the valves <NUM>, <NUM>. The valves <NUM>, <NUM> are controlled by the controller <NUM> via valve control circuits <NUM>, <NUM>, respectively. In some embodiments, when the valves <NUM>, <NUM> are control valves, the controller <NUM> is configured to control an opening of the valves <NUM>, <NUM> in order to control the flow and/or pressure in the system <NUM>. In some embodiments, the controller <NUM> will control the opening of the valves <NUM>, <NUM> in order to control the flow and/or pressure in the system <NUM> while concurrently controlling the speed and/or torque of the pump <NUM> in order to control the flow and/or pressure in the system <NUM>.

The accumulator <NUM> can be configured as any one of the exemplary embodiments of a motor-driven accumulator as discussed above. The accumulator <NUM> is controlled by accumulator control circuit <NUM> which can include the drive control for the prime mover of the accumulator, e.g., electric motor, hydraulic motor or another type of fluid driven motor. The controller <NUM> controls the operation of the accumulator via the accumulator control circuit <NUM>.

A common power supply (not shown) can provide power to the controller <NUM>, control valve assemblies <NUM>, <NUM>, the hydraulic pump <NUM> accumulator <NUM> and/or sensor assemblies <NUM>-<NUM>. In some embodiments, each component can have its own separate power supply.

Each of the control circuits <NUM>, <NUM>, <NUM> and <NUM> includes hardware and/or software that interprets the command signals from the controller <NUM> and sends the appropriate demand signals to the motor of pump <NUM>, valve <NUM>, valve <NUM> and the motor <NUM> of accumulator <NUM>, respectively. For example, the pump control circuit <NUM> can include pump curves and/or motor curves (e.g., motor curves for an electric motor) that are specific to the hydraulic pump <NUM> such that command signals from the controller <NUM> will be converted to an appropriate speed/torque demand signals to the hydraulic pump <NUM> based on the configuration of the hydraulic pump <NUM>. Similarly, the valve control circuits <NUM> and <NUM> can include valve curves and/or valve actuator curves that are specific to the valves <NUM>, <NUM>, respectively, and the command signals from the controller <NUM> will be converted to the appropriate demand signals based on the type of valve. The accumulator control circuit <NUM> can include motor curves (e.g., motor curves for an electric motor) and/or curves that are specific to the accumulator configuration, e.g., curves that take into account the dimensions, the pressure ratings, the flow ratings, thread pitch, outer-rotor or inner-rotor motor configuration, fixed accumulator shaft or rotating accumulator shaft, or other design criteria that are specific to the accumulator <NUM> or the application such that command signals from the controller <NUM> will be converted to an appropriate speed/torque demand signals to the motor of the accumulator <NUM>. The above-discussed curves can be implemented in hardware and/or software, e.g., in the form of hardwire circuits, software algorithms and formulas, or a combination thereof.

In some embodiments, the controller <NUM> and/or the control circuits <NUM>, <NUM>, <NUM> and <NUM> can include application specific hardware circuits and/or software (e.g., algorithms or any other instruction or set of instructions to perform a desired operation) to control the motor of pump <NUM>, the valves <NUM>, <NUM> and/or the motor <NUM> of accumulator <NUM>. For example, in some applications, the hydraulic cylinder <NUM> can be installed on a boom of an excavator. In such an exemplary system, the controller <NUM> can include circuits, algorithms, protocols (e.g., safety, operational), look-up tables, etc. that are specific to the operation of the boom. Thus, an input signal from an operator on the user interface <NUM> can be interpreted by the controller <NUM>, which sends the appropriate command signals to the motor of the pump <NUM>, the valves <NUM>, <NUM> and/or the motor <NUM> of accumulator <NUM> to position the boom at a desired positon.

The controller <NUM> can receive feedback data from concerning the operation of the pump <NUM>, the valves <NUM>, <NUM> and the accumulator <NUM>. For example, the controller <NUM> and/or the respective control circuits <NUM>, <NUM> can receive motor data such as revolution per minute (rpm), speed, frequency, torque, current and voltage, and/or other data related to an operation of a motor from the pump <NUM> and/or the accumulator <NUM>. In addition, if the motor <NUM> in the accumulator <NUM> is a servomotor, the controller <NUM> and/or the accumulator control circuit <NUM> can receive feedback on the exact positon of the motor <NUM> relative to the shell <NUM> of the accumulator <NUM>. For example, based on the pulses from the servo motor <NUM>, the rotational positon, i.e., the <NUM>-<NUM> deg. positon of the motor <NUM> and/or piston-plate <NUM> (depending on the configuration) relative to a reference point on the shell <NUM> can be calculated, and/or the longitudinal positon of the motor <NUM> and/or piston-plate <NUM> (depending on the configuration) along the longitudinal length of the shell <NUM> can be calculated, e.g., by counting the number of revolutions in comparison to the thread pitch.

In addition, the controller <NUM> and/or the control circuits <NUM>, <NUM> can receive feedback data from the control valves <NUM>, <NUM>. For example, the controller <NUM> and/or the control circuits <NUM>, <NUM> can receive the open and close status and/or the percent opening status of the valves <NUM>, <NUM>. In addition, depending on the type of valve actuator, the controller <NUM> and/or the control circuits <NUM>, <NUM> can receive feedbacks such as speed and/or position of the actuator. Further, controller <NUM> and/or the control circuits <NUM>, <NUM>, <NUM> and <NUM> can receive feedback of process parameters such as pressure, temperature, flow, or other parameters related to the operation of the system <NUM>. For example, each of the sensor assemblies <NUM>-<NUM> can measure process parameters such as pressure, temperature, and/or flow rate of the hydraulic fluid. The sensor assemblies <NUM>-<NUM> can communicate with controller <NUM> and/or control circuits <NUM>, <NUM>, <NUM> and <NUM> via wired or wireless communication connections. Alternatively, or in addition to sensor assemblies <NUM>-<NUM>, the hydraulic system <NUM> can have other sensors throughout the system to measure process parameters such as, e.g., pressure, temperature, flow, and/or other parameters related to the operation of the system <NUM>.

The communications between controller <NUM> and control circuits <NUM>, <NUM>, <NUM> and <NUM> can be digital based or analog based (or a combination thereof) and can be wired or wireless (or a combination thereof). In some embodiments, the control system can be a "fly-by-wire" operation in that the control and sensor signals between the controller <NUM> and control circuits <NUM>, <NUM>, <NUM> and <NUM> are entirely electronic or nearly all electronic. That is, in the case of hydraulic systems, the control system does not use hydraulic signal lines or hydraulic feedback lines for control, e.g., the valves <NUM>, <NUM> do not have hydraulic connections for pilot valves. In some systems, a combination of electronic and hydraulic controls can be used.

The inventive accumulator in the above exemplary embodiments allows the controller <NUM> to precisely control when and how much energy to inject into or remove from the system <NUM>. That is, unlike prior art accumulators that can only operate on a pressure differential between the system and the accumulator gas pressure, the exemplary embodiments of the present disclosure provide for an intelligent accumulator configuration that controls the distribution of flow and/or pressure as needed. Preferably, the controller <NUM> controls the magnitude, direction and/or duration of a pressure boost and/or a flow boost to and from the system by appropriately operating the motor <NUM> of accumulator <NUM>. Operation of the inventive accumulator <NUM> in the exemplary system <NUM> is discussed below.

If the hydraulic cylinder <NUM> travels in a direction in which the piston rod <NUM> is extended, the system will need to supply additional fluid in the system because the fluid returned to the pump <NUM> from retraction chamber <NUM> is less than the fluid needed for extraction chamber <NUM>. Accordingly, the pump <NUM> will lose pressure at its suction if the difference in the volume of fluid is not accounted for. In traditional systems, the stored energy in the form of compressed gas or a spring in the traditional accumulator will push stored fluid into the system due to the difference between the pressure in the accumulator and the pressure in the system. That is, the higher pressure in the traditional accumulator as compared to the system pressure will force the fluid to enter the system. However, in exemplary embodiments of the present disclosure, there is no stored energy. Instead, when the piston rod <NUM> is extending, the controller <NUM> will control the motor <NUM> of accumulator <NUM> such that the volume of chamber 19a decreases, e.g., by moving piston-plate <NUM>, and fluid is forced out ports 25a and 25b into the suction of pump <NUM>. For example, sensor assembly <NUM> can provide feedback of the pump suction pressure to controller <NUM>. When the pressure drops below a predetermined value, the controller <NUM> will control the motor <NUM> to move piston-plate <NUM> to force the fluid stored in accumulator <NUM> into the system <NUM> to raise the pressure in the system to the operational setpoint. Of course, the controller <NUM> can be configured to also anticipate the need for more fluid in the system <NUM> and take appropriate action with respect to accumulator <NUM>. For example, when the command to extract hydraulic cylinder <NUM> is given, the controller <NUM> can also send a command to motor <NUM> via accumulator control circuit <NUM> to move piston-plate <NUM> to force fluid into the system <NUM>.

Conversely, if the hydraulic cylinder is retracted, fluid is sent to retraction chamber <NUM> and extracted from extraction chamber <NUM>. Because the volume of the extraction chamber <NUM> is greater than that of retraction chamber <NUM> due to the piston rod <NUM>, there will be excess fluid in the system, which will cause the pressure in the system to rise. When the pressure at sensor assemblies <NUM> or <NUM> increases above a predetermined value, the controller <NUM> will control motor <NUM> via accumulator control circuit <NUM> to move the piston-plate <NUM> such that chamber 19a in accumulator <NUM> is expanded. By expanding chamber 19a, fluid from the system <NUM> can enter the accumulator <NUM> for storage and maintain the system at the operational setpoint. Of course, the controller <NUM> can be configured to also anticipate the need for less fluid in the system <NUM> and take appropriate action with respect to accumulator <NUM>. For example, when the command to retract hydraulic cylinder <NUM> is given, the controller <NUM> can also send a command to motor <NUM> via accumulator control circuit <NUM> to move piston-plate <NUM> such that fluid is forced into the accumulator <NUM> via ports 25a and 25b. Of course, the controller <NUM> can command motor <NUM> to move piston-plate <NUM> even if the hydraulic cylinder <NUM> has not moved. For example, the controller <NUM> can sense the pressures, temperatures and flows in the system from sensor assemblies <NUM>-<NUM> and take appropriate adjustments to the positon of piston-plate <NUM> to reduce or eliminate pressure and/or flow disturbances in the system <NUM>.

In either direction of operation, i.e., injecting fluid into the system piping or extracting fluid into chamber 19a, the motor <NUM> can be operated to move piston-plate <NUM> such that the pressure boost and/or flow boost is precisely controlled in order to minimize shocks and/or erratic system operation. For example, when injecting fluid into or extracting fluid from the system piping, the controller <NUM> can operate motor <NUM> to move piston-plate <NUM> so as to produce a slow flow rate to, e.g., minimize any shock or erratic behavior in the system. Alternatively, if a slow flow will lead to a shock or erratic behavior in the system, the controller <NUM> can operate the motor <NUM> to move piston-plate <NUM> so as to produce a fast flow rate. If the change in pressure or flow is temporary or within acceptable upper and lower limits, the controller <NUM> can take no action with respect to moving piston-plate <NUM> to prevent erratic operation.

In some embodiments, the controller <NUM> can control the piston-plate <NUM> to cancel any pressure waves that could shock and/or damage the system <NUM>. For example, if the hydraulic cylinder <NUM> controls a boom of an excavator that suddenly hits a rock, the pressure shock wave could damage equipment in the system such as the pump <NUM> and the valves <NUM>, <NUM>. To prevent such damage, sensors in the system <NUM> can inform the controller <NUM> that the boom has stopped abruptly at which point the controller <NUM> can operate motor <NUM> to move piston-plate <NUM> to induce an "inverse" pressure wave into the system piping to cancel the pressure wave caused by the rock. Of course, the pressure wave cancellation feature is not only for sudden abnormal events. Pressure waves created in normal operation can also be cancelled to provide smoother, more efficient operation. For example, any pressure waves due to the operation pump <NUM> and valves <NUM>, <NUM> can be cancelled to provide smoother operation by appropriately controlling motor <NUM>. Thus, unlike prior art accumulators, embodiments of the present disclosure provide for an "intelligent" accumulator that can be controlled to eliminate or minimize problems due to pressure and/or flow disturbances in the system.

Claim 1:
A fluid system (<NUM>), comprising:
a fluid-driven actuator;
a pump (<NUM>) that is fluidly connected to the fluid-driven actuator;
an accumulator (<NUM>) fluidly connected to the pump (<NUM>), the accumulator (<NUM>) having,
a shell (<NUM>) that defines an interior volume (<NUM>), the shell (<NUM>) including at least one port in fluid communication with the fluid system (<NUM>),
an accumulator shaft disposed in the interior volume (<NUM>) and extending at least partially across the interior volume (<NUM>) from a first interior surface of the shell (<NUM>) along a longitudinal axis of the shell (<NUM>),
a piston-plate (<NUM>) disposed in the interior volume (<NUM>) such that the piston-plate (<NUM>) and a second interior surface of the shell (<NUM>) define a chamber in the interior volume (<NUM>), the chamber (19a,19b) in fluid communication with the fluid system (<NUM>) via the at least one port, and
a motor (<NUM>) coupled to the piston-plate (<NUM>) and having a shaft (<NUM>) that interfaces to the accumulator shaft and having an outer radial surface (<NUM>) that interfaces to an interior surface of the shell (<NUM>), a rotational movement of the motor (<NUM>) translating to a linear movement of the piston-plate (<NUM>) along the accumulator shaft such that a volume of the chamber (19a, 19b) varies based on a position of the piston-plate (<NUM>), a decreasing chamber volume injecting fluid into the system (<NUM>) via the at least one port and an increasing chamber volume receiving fluid from the system (<NUM>) via the at least one port for storage in the chamber (19a, 19b); and
a controller (<NUM>) that controls the motor (<NUM>) to establish the position of the piston-plate (<NUM>) along the accumulator shaft to control at least one of a magnitude, a direction and a duration of at least one of a pressure boost and a flow boost in the system (<NUM>), characterised in that:
the motor (<NUM>) is an outer-rotor type motor and the interface between the inner surface of the shell (<NUM>) and the outer radial surface (<NUM>) of the motor (<NUM>) is a threaded interface (<NUM>).