Patent Application
20230375011
In describing power controllers, it is helpful to consider some terms relative to the fluid power industry, some of which are familiar and some of which will be new. These terms are defined below and will be used throughout this document.
In most fluid power systems, there is more energy available than is needed to do the work. When this energy is stored (potential energy), there is no waste. But when excess energy is directed to an actuator, it produces acceleration to a higher velocity than is desired. The extra energy must be neutralized, either before the actuator (meter-in) or after the actuator (meter-out). It is this characteristic of energy transfer with fluids that results in much of the energy loss in fluid power systems.
A fixed displacement pump operating at a specific rpm will produce a relatively constant flow. Resistance to that flow will cause the pump to charge each unit volume with the pressure necessary to push it out. This pump has a fixed flow and a variable pressure.
Hydraulic systems that use a fixed displacement pump to push UE's to an actuator may be designed to be relatively efficient when the actuator uses all the UE's coming from the pump. The losses would be from the inefficiency of the components and pressure losses through the conductors, but there would be no adjustment of the actuator velocity.
When it is necessary to have velocity control, inefficiency increases. The fixed displacement pump must be sized to provide enough flow for the maximum velocity and the prime mover must be sized to drive the pump at the maximum pressure. This means that there are times when more power is being put into the system than is needed. All the UEs leaving the pump will be charged with enough pressure to move the load but not all the UE's will be used. The unused UE's will be diverted back to the reservoir at low pressure. Whenever a pressurized UE is directed to an area of lower pressure without doing work, there is an energy transfer in the form of heat. With pneumatics, this is an endothermic transfer. With hydraulics, this is an exothermic transfer.
To save energy, variable displacement, pressure compensated pumps have been developed. They provide a variable flow at a fixed pressure. These pumps change displacement so that the UE flow matches the velocity requirements, but at maximum pressure. The UE's leaving the pump each have a higher energy level than is needed. The volume of fluid is needed to move the actuator but at a lower energy level to prevent too much acceleration. The flow rate of UE's must not change but each UE must reduce its charge of pressure. This is accomplished by means of an orifice. It takes energy to squeeze UE's through an orifice. The energy is consumed as a pressure loss and is dissipated as heat. The UE's downstream of the orifice have a lower energy density than the UE's entering the orifice. The volume of fluid did not change but the power level was reduced. The pressure compensated pump is an improvement over the fixed displacement system. Power control with fixed displacement is a waste of both volume and pressure. Pressure compensated systems reduce the waste of volume and only waste the energy derived from pressure.
Another prior art improvement was made with the development of the load-sensing pump. This pump limits both the flow and pressure to match the power (velocity) requirements of the actuator. The load-sensing pump maintains a pressure that is about 10% higher than the load-induced pressure, so it still requires a restrictive orifice to squeeze off extra energy. When used in a system where there is more than one actuator, the load-sensing pump maintains a pressure that is about 10% higher than the highest pressure requirement. This can dramatically increase the energy loss. It is an improvement over the pressure compensated pump but both use orifices to consume excess energy.
Some prior art systems address the limitations of the load-sensing pump by supplying a single load-sensing pump for each actuator. This has drawbacks. It increases cost, increases plumbing, increases weight, and takes up a lot of space. In addition, each pump still has at least a 10% energy loss through a restrictive orifice.
A common approach in the prior art to deal with to the problem of efficiency is the use of variable speed electric motors. Using fixed displacement pumps, these motors adjust their speed to provide the actuators with the correct flow with pressure determined by the resistance. The limitations of these systems are that they are not able to accommodate the specific needs of more than one actuator at a time, the motors must be sized for maximum load, they make no provision for storing energy, and the controls require electronic equipment that add cost and take up space.
With improvements in electrohydraulic equipment, some manufacturers are offering actuators with attached hydraulic power units. Each self-contained power unit has a variable speed motor attached to a fixed displacement pump. The motor rpm determines flow rate, and the resistance determines the pressure. The limitations are that the actuators must be modified to accept the mounted power units, there is a substantial increase in installed cost, they are not practical as a retrofit to existing systems, and there is no provision for energy storage.
The Digital Displacement® pump was developed to match the power requirements to one or several actuators. It has some remarkable characteristics, but it can only be controlled by a computer. It has no value in the storage and controlled release of UE's.
A known advantage of fluid power, both hydraulic and pneumatic, is the ability to store energy. A system can be analyzed to determine the average power requirement and then a power unit can be made that will supply an average flow rate. When the demand is less than the average suppled flow, the extra UE's are stored in an accumulator (hydraulic) or a receiver (pneumatic). Then when demand is higher than the average, UE's are drawn from storage. This type of system usually saves energy, but in current implementations in the industry there are inherent inefficiencies. For the stored energy to be used, the UE's must be at a higher energy level than is required by the load. As with the devices described above, the excess energy in the UE's must be reduced as they are squeezed through an orifice. The energy is lost as heat.
When a load has been lifted by an actuator, it has potential energy (PE). When the load is lowered, the PE becomes KE in the fluid and the energy is drained away to the reservoir (hydraulic) or to atmosphere (pneumatic). Whether the descent is controlled or allowed to free-fall, all the energy used to raise the load is dissipated as heat passing through an orifice, or as a shock wave as the load strikes the bottom. The common method in hydraulics is to use a counterbalance valve for a controlled descent. This is a modulating orifice that dissipates the energy as heat. With pneumatics, an orifice is placed in the line that dissipates the energy by taking on heat. In either case, it is analogous to using the brake as a car goes downhill.
All the prior-art systems described have one thing in common. They all control power by reducing the amount of energy in the UE's from the source by transferring the energy in the form of heat.
Reference is now made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings. It is emphasized that various features may not be drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion. In addition, it is emphasized that some components be omitted in certain figures for clarity of discussion. Reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
Although similar reference numbers may be used to refer to similar elements for convenience, it can be appreciated that each of the various example embodiments may be considered distinct variations.
In
In
Once the piston/cylinder actuator 102/104 reaches the end of its stroke, the Δp would be zero and the pressure in the cylinder 102 would rise to the level of the source pressure. The power was controlled, but twice the amount of energy was used as was necessary. When the piston 104 completely extends, the pressure will rise to that of the source and produce twice the necessary force.
The Variable Displacement Power Controller (VDPC) embodiments disclosed in the present application are different from the prior art approaches described above. The VDPC embodiments do not reduce the energy in the UE's but instead can be used to reconfigure or distribute the energy to provide improved efficiency and flexibility in their implementations.
The concept of the Variable Displacement Power Control (VDPC) is to recognize fluid energy as a product of pressure and volume (pV). The amount of energy stored as potential energy (PE) or used as kinetic energy (KE) can be expressed as energy units (UE's). The available energy can be in the form of high pressure/low volume UE's or low pressure/high volume UE's. VDPCs make it possible to produce the energy in the most practical and efficient way and then convert or reconfigure the UE's to whatever is needed for the work to be done. When the UE's are stored or supplied at a pressure higher than is required by the load, the VDPC will reconfigure them into a lower pressure and increased volume. When the UE's exist at a pressure that is lower than what is required by the load, a VDPC will increase the pressure and reduce the volume. This provides the opportunity to produce energy at the most efficient level and then convert the energy into the most efficient form required for the work.
The VDPC embodiments described in the present patent application consider the total energy required for the work, designs for the most appropriate method of producing that energy, and then distributes the energy with an improved efficiency as described herein.
As will be further described in the embodiments below, the VDPC embodiments of the present application comprise rotating members encasing vanes, pistons, gears or other positioning/tensioning elements that travel around the inside of a cam ring having multiple lobes. This arrangement produces distinct displacement chambers, each of which may be pressurized and each of which has a port out of the VDPC. The cam ring and the rotating group comprising the rotating members and encased vanes or pistons are movable relative to each other to alter the ratio of displacements among the chambers.
For exemplary purposes, the operation of an embodiment of a VDPC is described below in the context of
Still referring to
With further reference to
Pressurized fluid entering any chamber induces a torque on the rotating group 580, which is distributed to the vanes 560 or pistons (in other embodiments pistons are used in the place of the vanes illustrated in the current embodiment). It is the common torque on the rotating member group 580 that enables UE's to be reconfigured.
A UE is a product of force and a unit volume (F/V), i.e., N/mm3 or lb./in3. It is a unit of work, either kinetic or potential. For example, 1000 pressure units acting on 1 unit volume contain the same amount of energy as 100 pressure units acting on 10-unit volumes. 1000F×1V=100F×10V. UE's flowing at a certain rate are simply units of work that occur over a certain amount of time, in other words, Units of Power (UP).
A certain volume at a certain flow rate is necessary to move an actuator in a certain amount of time. In the prior art, the source volume/flow rate is considered mandatory, leaving only pressure reduction as the means of velocity (power) control. The use of the VDPC makes it possible to reconfigure the source volume/flow and pressure (UE's and UP's) to match the velocity requirements of the actuator without the pressure reduction and consequent energy loss.
For illustration purposes, consider the arrangement of a VDPC 500 with its rotor 520 positioned at the center of the oblong power exchange cavity 515, such as being fixed at the halfway point of the straight-wall section 555. Further in this illustrative configuration, configuring the application to have pressurized UE's entering at Port 1 with Port 3 connected to a reservoir (not shown, see, e.g.,
The VDPC can also reconfigure a UE into a higher pressure, reduced volume. Again, for purposes of illustration placing the rotating member 580 at the center of the oblong power exchange 515 and 516, by arranging the device so that Port 1 and Port 3 are both connected to the source at 1,000 pressure units and Port 2 is directed to the reservoir, a UE entering Port 1 at 1,000 units will be reconfigured as 0.5 UE's at 2,000 pressure units as it leaves Port 4. The output from Port 4 will be half the volume at twice the pressure.
The VDPC can also be used as an adjustable proportional power divider when it is desired to synchronize actuators. For example, in a four-chambered VDPC as described above, if the flow to Port 1 and Port 3 is from the same source, the output flow at Port 2 and Port 4 will be equal even if the pressure is different at each port. The input pressure will be the average of the output pressures. The DPC reconfigures the input UE's into what is required at each outlet. This embodiment does not provide velocity control, but power proportioning.
The VDPC can also be used as a disproportionate power divider to operate two actuators at different relative speeds. Given two motors of equal displacement where one is to operate at 1800 rpm and the other to operate at 900 rpm. The VDPC 500 would be arranged with the rotating group 580 moved within the oblong chamber 515 and 516 toward Chambers 3 and 4. The common input to Ports 1 and 3 could be divided, e.g., so that twice as much flow would go to Port 2 as would go to Port 4.
Whether used as a proportionate or disproportionate power divider, when the actuators are reversed, the VDPC will combine the flows from the actuators in the same ratio as it divided.
As seen in these equations, for any given power and velocity (P and N or P and V), there is a distinct product of pressure and displacement (pd) or pressure and diameter2 (pd2). When an actuator has a fixed displacement, the only variable is the pressure. And so, with a fixed displacement motor or a cylinder, velocity, linear or angular, is determined by the amount of available pressure differential. The VDPC modulates the power going to an actuator by reconfiguring the input UE's to match the pressure for the target velocity. Velocity becomes the controlling factor.
In the prior art, pneumatic systems waste energy differently than hydraulic systems. Hydraulic systems waste energy when the fluid moves from higher energy (larger UE value) to lower energy (smaller UE value) without doing work. Pneumatic systems waste energy in three primary ways: First, when the air is compressed, it becomes heated, and that heat is dissipated as the gas travels through the system. This accounts for substantial energy loss before any work is done. Secondly, leakage, both external and internal, is a source of wasted energy with higher pressures contributing to greater loss. The third reason pneumatic systems waste energy is the practice of storing the UE's at a higher pressure than is necessary for the work. Velocity is then controlled by restrictive power controls.
Referring still to the prior art, some of the pneumatic energy loss can be mitigated by placing pressure regulators before the actuators to provide just enough UE strength for acceleration and then applying restrictive orifices to limit the final velocity.
In contrast, the use of the VDPC makes it possible to produce the UE's, either hydraulic or pneumatic, at a pressure that allows the pump or compressor to operate at its highest efficiency. The UE's are then reconfigured to match the power requirement of each individual actuator. For a pneumatic system, this may mean storing the energy at relatively low pressure which reduces the energy lost as heat and minimizes the internal and external leakage. A VDPC can then be used as a pressure intensifier to provide a higher power density to those actuators that require it. A VDPC embodiment as disclosed in the present application could also then be used at the actuator exhaust, providing the necessary resistive load to control velocity. This addresses all three areas of pneumatic system energy waste.
There are several ways to control a VDPC, depending on various factors including the level of accuracy required. Illustrated in
If more accuracy is needed, feedback from the actuator such as from a tachometer (rotary) or linear transducer (linear) can be used to control the orifice 610 or to directly control the VDPC 500. For example, a piston could impart force on one end of the VDPC 500 with the force of an opposing spring on the other end, or any other number of actuators and control systems could be used such as pistons on either side or other controlled pumps, cylinders, pistons, or controllable flexible membranes.
Below in the specification and accompanying figures various advantageous applications of VDPCs are disclosed in which an embodiment VDPC 500 either makes such applications possible or makes such applications synergistically improved and efficient over known prior art approaches.
When the directional valve 704 is shifted from the center position 720 in the middle of the directional control valve, to either of the flow direction positions 730740, flow is directed to the motor 770, and Port 1 504 receives UE's from the source, discharging them through Port 2 506. Port 3 508 is connected to the reservoir 720 by way of the return line 725 and draws in fluid which is then exhausted under pressure to Port 4 510. As shown in
The default condition of the VDPC 500 is for maximum flow from Port 1 504 to Port 2 506. There is a small flow from Port 2 508 to Port 4 510 at the default condition. The result is that full source pressure is available to the motor at start-up providing rapid acceleration for the motor.
As the motor 770 approaches the desired rpm, the velocity signal 750 (such as from a tachometer) begins to modulate the position of the rotating group 580 within the PEC 515 and 516 (not shown, see
For example, a motor with a displacement of 50 cm3 operating at 1550 rpm at a pressure of 15 MPa, will require 50 cm3×1550 or 77,500 cm3×15 MPa UE/min. This equals 1,162,500 UE's/min. If the source is at a pressure of 20 MPa, each cm3 is charged with 133% more energy than is needed. Only 58,125 of the source UE's are needed for the job. The VDPC reconfigures 58,125 UE's/min at 20 MPa into 77,500 UE's/min at 15 MPa by drawing in 19,375 cm3/min from the reservoir.
Meter-in power control may be used for hydraulic motors that do not need resistive pressure to prevent a run-away event. A motor case drain may not be required.
As the motor approaches the target rpm, the velocity signal causes the oval cam to shift, reducing the displacement of chambers 1 and 2. With less flow from Port 1 504 to Port 2 506, more flow is driven through Port 3 508 to Port 4 510. Port 4 510 is at source pressure 702. The pressure at Ports 1 and 3 is designed to be great enough to provide enough torque on the rotating group 580 to drive flow out of Port 4 at source pressure. This produces the necessary resistive pressure at the motor exhaust to counteract the high source pressure.
The UE's exhausting from the motor are designed to have the pressure necessary to resist the acceleration and maintain the correct motor rpm. However, these UE's are not consumed as heat as with a restrictive orifice but are reconfigured into a reduced volume at the same pressure as the variable flow source 702.
For example, a motor with a displacement of 50 cm3 operating at 1550 rpm at a pressure of 15 MPa, will require 50 cm3×1550 or 77,500 cm3×15 MPa UE/min. This 1,162,500 UE's/min. It takes 50 cm3 to rotate the motor one revolution. If the source is at a pressure of 20 MPa, each cm3 is charged with 133% more energy than is needed. A resistive load of 5 MPa will be required to reduce the acceleration and maintain velocity.
77,500 cm3/min are needed, but there is enough energy in 58,125 cm3/min of the source to do the job.
The VDPC receives the 77,500 cm3/min at 5 MPa from the motor, diverts 58,125 cm3/min at 0 MPa to the reservoir, and intensifies 19,375 cm3/min from 5 MPa to 20 MPa to be fed into the line from the source. This reduces the flow taken from the source to 58,125 cm3/min.
Meter-out power control is used for motors that need resistive pressure to prevent a run-away event. A motor case drain 810 may often be required in this application 800.
When the directional valve 704 is shifted from its center position 720 to either of its directional positions 730740, Port 1 504 receives UE's from the source 702 and discharges them through Port 2 506. Port 3 508 is connected to the reservoir and draws in fluid which is then exhausted under pressure to Port 4 510. Port 2 is combined with Port 4.
The default condition of the VDPC 500 is for maximum flow from Port 1 to Port 2. There is a small flow from Port 3 to Port 4 in this default condition. The result is that full source 702 pressure is available to the cylinder 910 at start-up providing rapid initial acceleration.
As the cylinder approaches the desired translational speed, a velocity signal 750 begins to modulate position of the rotating group 580 within the power exchange cavity 515, e.g., in the current rendering moving the rotating group 580 (not shown, see
For example, a cylinder with a volume of 1,000 cm3 must extend at 0.5 m/sec at a pressure of 15 MPa. The variable source pressure from a PC pump or an accumulator is at 20 MPa. The amount of work to be done is 15 MPa×1,000 cm3 or 15,000 MPa/cm3. There is enough energy in 750 cm3 at the source to do the job, but 1,000 cm3 are needed to fill the cylinder.
The VDPC reconfigures 750 UE's at 20 MPa into 1,000 UE's at 15 MPa by drawing 50 cm3 from the reservoir and adding it to the flow to the cylinder 910.
If the load on the cylinder 910 changes, and/or the pressure at the variable source changes, the velocity signal 750 can automatically cause the VDPC 500 to adjust to control the speed.
If a different velocity is needed for the cylinder to retract, a new signal 750 can be sent to the VDPC. The signal could also be changed while the cylinder is moving for profiling.
As described in the above applications, the direction control module 704 has a center position 720 and first and second directional positions 730740 that cause the double acting cylinder to extend or retract. The default condition of the VDPC 500 is to allow maximum flow from Port 1 to Port 2, so fluid passes through the VDPC 500 to the reservoir with little restriction. This results in full source pressure to the cylinder which provides initial rapid acceleration.
As the cylinder 910 approaches a target speed for the designed application, a velocity signal 750 causes the rotating group 580 within the PEC 515, e.g., in the current rendering the rotating group 580 is moved “upward” from the Port 3/Port 4 side of the VDPC to the Port 1/Port 2 side, thereby reducing the displacement of Chamber 1 and Chamber 2 (not shown, see, e.g.
The resistive energy is not wasted, but is instead reconfigured, reducing the energy taken from the source.
For example, a cylinder with a cap end volume of 1,000 cm3 and a rod end volume of 700 cm3 must extend at 0.5 m/sec at a pressure of 10 MPa. The variable source pressure from a PC pump or an accumulator is at 20 MPa. The amount of work to be done is 10 MPa×1,000 cm3 or 10,000 MPa/cm3. There is enough energy in 500 cm3 at the source to do the job, but 1,000 cm3 are needed to fill the cylinder.
The VDPC 500 receives 700 cm3 at 14.29 MPa from the rod end 930 of the cylinder extending, diverts 200 cm3 at 0 MPa to the reservoir, and intensifies 500 cm3 from 14.29 MPa to 20 MPa to be fed into the line from the source. This reduces the volume taken from the source to 500 cm3.
Retracting the cylinder causes the VDPC 500 to receive from the cap end 1,000 cm3 at 4 MPa which is 4,000 MPa/cm3 units of work, while the rod end receives 700 cm3 at 20 MPa for 14,000 units of work. The VDPC diverts 800 cm3 to the reservoir at 0 MPa and intensifies 20 cm3 to 20 MPa which is fed to the source line. The volume from drawn from the source is reduced to 500 cm3.
If the load on the cylinder 910 changes, and/or if the pressure at the variable source 702 changes, the velocity signal 750 may be configured to automatically causes the VDPC 500 to adjust to control the speed.
If a different velocity is needed for the cylinder to retract, a new signal 750 can be sent to the VDPC 500. The signal could also be changed while the cylinder is moving for profiling.
In the disclosed present embodiments, a VDPC 500 receives the UE's from the fixed source 702 and reconfigures them into an optimum energy level. Flow from the source 702 drives the fluid from Port 4 to Port 3 creating torque on the rotating group 580 (not shown, see
The default position of the VDPC 500 is for minimum displacement at Ports 4 and 3 (Chambers 4 and 3—see, e.g.,
The addition of a selector valve 1100 in
In the illustrated embodiment, an accumulator stores the kinetic energy captured by the VDPC 500 as it provides the resistance to the movement of the load.
In this circuit, the VDPC is in the return line from the directional control valve. It functions as a meter-out velocity control. It causes the actuator to draw only the energy needed to move the load. When the load is lowered, no energy is needed from the source. The VDPC resists the load, not by dissipating the energy, but by using the energy to drive the VDPC as an intensifier, pushing the energy back into the source. The VDPC provides velocity control extending and retracting as well as energy recovery when the load is lowering or over-center.
This approach divides the flow to fixed displacement motors 770 in proportion to the displacements of Chambers 1 and 2 and that of Chambers 3 and 4 (not shown, see
The VDPC 500 also combines the reverse flow from the motors 770 in the same proportion. The actuator velocity is the same in both directions and is determined by the flow from the source and the proportional division between the fluid flows as defined by the VDPC adjustment. The illustrated embodiment 1300 of
Lifting the load means directing the charged UE's from the accumulator 1408 through the VDPC 500, using the reducing function. Upon lowering the load, the UE's exhausting the cylinder 1410 are directed back through the VDPC 500 where they are intensified and return the energy to the accumulator 1408.
Energy is saved lifting the load by only using the source energy necessary. Energy is saved when lowering the load as the KE is sent back to the accumulator 1408.
The VDPC is controlled by the Δp across an orifice. The location of the higher and lower pressures depends on the direction of flow. Shuttle valve 1430 reveals the upstream (higher) pressure while shuttle valve 1420 reveals the downstream (lower) pressure. These two opposing pressures position the rotating group 530 within the power chamber 515. A change in the Δp in either direction would result in a change of position of rotating group 530.
In the center condition (shown) the switching module 1404 holds the cylinder in place. When the switching module 1404 is shifted to the right, fluid from the accumulator 1408 is directed across the orifice. Shuttle valve 1430 directs the higher pressure to the velocity signal port of the VDPC 500. Suttle valve 1420 directs the lower pressure to the opposing side of the VDPC 500. With the direction of flow from Port 1 to Port 2 540, the VDPC functions as a pressure reducer, limiting the rate of flow to the cylinder.
Shifting the switching module 1404 completely to the left allows high pressure fluid in the cylinder to return through Ports 4 550 and 2 540 of the VDPC 500. Flow from Port 1 535 returns through the orifice and flow from Port 3 545 is directed to the reservoir. Shuttle valve 1430 sends the pressure upstream from the orifice to the velocity signal port on the VDPC 500. Shuttle valve 1420 sends the downstream pressure to the opposing side of the VDPC 500.
With the direction of flow from Ports 4 550 and 2 540 to Ports 1 535 and 3 545, the VDPC 500 functions as a pressure intensifier. This increases the power density of the UE's which can now be recovered and put back in storage in the accumulator 1408.
Once the cylinder is lifted, the potential energy is recovered each time the cylinder is lowered with only the mechanical inefficiencies being made up by the source flow 702.
Using the VDPC 500 in this manner, a very large cylinder with a heavy load can be lifted and lowered very quickly and repeatedly using an accumulator 1408 and a very small source flow 702. The source flow would be sized to only accommodate the mechanical and volumetric inefficiencies.
While the above applications describe preferred embodiment applications of the VDPC embodiments disclosed in the present application, the embodiments disclosed herein provide a number of general advantages that are further described below in
A very important function of the VDPC is to allow the most efficient components to be used to supply the energy. Many of the hydraulic pumps are designed so that they operate most efficiently at higher pressures, sometimes much higher than is required by the work being done. The embodiment of
The
The
The
Without loss of generality of the foregoing applications that were generally described as being hydraulic systems, for illustration purposes the following applications are described in the context of exemplary pneumatic systems.
In the embodiment implementation using a VDPC as disclosed in the present application, however, a VDPC can be used as both a pressure reducer and a pressure intensifier to make the greatest use of the stored energy. When the gas pressure drops below the required actuator pressure, the VDPC is switched from reducing to intensifying by means of the selector valve 1650 which receives a pressure indication from the pressure meter 1660.
This embodiment makes it possible to save energy and component cost in at least two other ways: Some systems have varying power requirements but without enough dwell time to justify the use of an accumulator. In these cases, the average load can be determined and a pump that is designed to efficiently convey that average power can be used in conjunction with an accumulator. Both the accumulator and the pump will operate at the most efficient power density and the VDPC 500 can reconfigure the power density needed for the system without the use of restrictive orifices.
Referring now to
In the improved system of
A major advantage of fluid power is the ability to have a central power source and then distribute that power to multiple locations and produce both rotary and linear motion. In the prior art, when a single pump is used to supply the fluid, it must be sized for maximum system flow and pressure. When more than one actuator is being operated, the pump must move the fluid at the maximum required pressure and any excess energy must be dissipated. A conventional way to mitigate this is by providing each actuator with its own pump, all driven by a common prime mover. This approach has several limitations as the number of actuators increases. For example, there are only so many pumps that can be mounted on a prime mover and these all add weight and take up valuable space. With single or multiple pumps, there is still the need for restrictive orifices to consume energy and control velocity.
Another method of reducing the energy loss in the prior art is to provide a separate small power unit for each actuator. This also has its limitations as it increases weight and complexity with the addition of the necessary electronic controls. The actuators must be designed to incorporate the power units, and this makes it impractical for retrofitting to an existing system with a central power unit.
This present patent application describes a VDPC-facilitated multiple actuator system that mitigates the above-described disadvantages of conventional approaches and provides the following advantages:
There is a difference between gas and liquid and this difference changes the way we apply the VDPC. When a gas is compressed, it becomes heated. This heat accounts for about 10% of the available UE's. The heat is usually dissipated as the gas moves through the piping and as it rests in the receiver. The amount of heat energy generated and then lost is directly proportional to the compression ratio.
In both hydraulics and pneumatics, energy units (UE's) are produced and stored at a higher pressure than is needed for the work to be done. There is very little compressibility with liquids and the standard method in hydraulics is to control the excess energy by squeezing of the pressure through an orifice. A gas is compressible and the amount of energy in the system is directly proportional to the quantity of gas molecules under compression. The power to an actuator can be controlled by a regulator which limits the quantity of molecules that are released. Pressure is the result of molecular density. The regulator reduces the density which results in a lower pressure but without the energy loss. But a regulator has no ability to increase molecular density. The compressor must supply the molecular density that meets the highest pressure requirement in the system and then depend on the regulator(s) to limit the pressure to the actuators.
It takes a higher energy density to accelerate a load than to maintain velocity. The regulator must be set at a molecular density high enough to accelerate the actuator. But to control velocity, restrictive orifices must be applied to limit the rate at which the molecules are used.
A VDPC can reduce the energy losses in pneumatic systems in two ways. The PE stored in the receiver is the product of volume and pressure. The compressor can be operated at a relatively low pressure which will increase its efficiency and reduce the energy lost as heat. Low pressure also reduces the air lost through leakage throughout the system. The VDPC can then function as a pressure intensifier for those actuators that require a greater power density. The VDPC is then used as velocity control at the actuator to use only the energy needed for the job. This is illustrated in the circuit on the left.
Referring now to
Referring specifically now to
In this present embodiment, the rotor 520 is generally circular and rotates within the cam 1920, with the interior space of the cam defining a power exchange cavity 515 and 516 within which the rotor 520 rotates and engages with an inner wall 1930 of the cam 1920 through the vanes 560. Pressure within the vane slots 530 keep the vanes 560 engaged by spring tension and/or pressurizing the vane slots 530 internally or externally to maintain contact with the power exchange cavities 515 and 516.
The cam 1920 itself has flat sides 1970 that are slidably movable along inner flat sides 1940 of an outer casing 1950. In this embodiment, the the rotor 520 is rotatably concentric to the shaft 585, and thus movement of the cam 1920 is relative to the outer casing 1950 causes translation of the relative positions of the cam 1920 to the power exchange cavities 515 and 516 formed in the inside of the cam 1920. In this illustrated figure, and for purposes of discussion only, this translation would be in the “y” axis direction.
The movement of the cam 1920 relative to the rotor 520 may be imparted by pistons 1960 that engage with flat portions 1970 of the housing 1920 to control the variability of the four chambers 535,540,545,550. Illustrated in the present
As described above, the ports can be flexibly configured such that a source of fluid might, e.g., enter Cavity 1 535 through a first port and push the fluid over to Cavity 2 540 and out a second port, turning the rotor 530 by the vanes 560. This rotation of the rotor 520 and vanes 560 in turn can provide a pumping action to pull fluid from another source into Cavity 3 545 and over to Cavity 4 550 and out through a fourth port. As mentioned, the corresponding ports will be further described in subsequent figures relating to this embodiment.
One design attribute of this embodiment is to provide that the intra-vane distance is substantially equal to than the distance between the ports.
In one embodiment, the embodiment for a four-port variable displacement power controller as shown in
While many of the embodiments described herein are rotor/vane embodiments where vanes rotate inside cams to move fluids or gases through liquid passages, the present application anticipates that the principles disclosed herein can be applied to a piston unit approach.
As shown in
Illustrated in
As disclosed above with respect to other embodiments, in this implementation the cam ring 2120 has translational freedom of motion in the “y” axis direction of the page as shown in the present figure as the flat portion 2170 moves along the flat portion of the housing 2170 along the straight-walled section 2190. The translational pistons 2160 (as distinguished from the cavity pistons 2185) can be controlled and actuated as described in prior embodiments to accomplish the expansion and contractions of the cavities and of the first and second cavity pairs 535-540 and 545-550. With the adjustable ratios between the first and second cavity pairs, this VDPC can be used in the various system application that have been described herein, as well as in other system applications that flow from the properties of this rotor/cylinder block implementation 2100. Collectively the rotor 2085 and rotor pistons 2185 form a rotational group 2180.
The concept of the Variable Displacement Power Control (VDPC) is to recognize fluid energy as a product of pressure and volume (pV). The amount of energy stored as potential energy (PE) or used as kinetic energy (KE) can be expressed as energy units (UE's). The available energy can be in the form of high pressure/low volume UE's or low pressure/high volume UE's. VDPCs make it possible to produce the energy in the most practical and efficient way and then convert or reconfigure the UE's to whatever is needed for the work to be done. When the UE's are stored or supplied at a pressure higher than is required by the load, the VDPC will reconfigure them into a lower pressure and increased volume. When the UE's exist at a pressure that is lower than what is required by the load, a VDPC will increase the pressure and reduce the volume. This provides the opportunity to produce energy at the most efficient level and then convert the energy into the most efficient form required for the work.
The VDPC embodiments described in the present patent application consider the total energy required for the work, designs for the most appropriate method of producing that energy, and then distributes the energy with an improved efficiency as describe herein.
Various terms used herein have special meanings within the present technical field. Whether a particular term should be construed as such a “term of art,” depends on the context in which that term is used. “Connected to,” “in communication with,” or other similar terms should generally be construed broadly to include situations both where communications and connections are direct between referenced elements or through one or more intermediaries between the referenced elements. These and other terms are to be construed in light of the context in which they are used in the present disclosure and as those terms would be understood by one of ordinary skill in the art would understand those terms in the disclosed context. The above definitions are not exclusive of other meanings that might be imparted to those terms based on the disclosed context.
Words of comparison, measurement, and timing such as “at the time,” “equivalent,” “during,” “complete,” and the like should be understood to mean “substantially at the time,” “substantially equivalent,” “substantially during,” “substantially complete,” etc., where “substantially” means that such comparisons, measurements, and timings are practicable to accomplish the implicitly or expressly stated desired result.
Additionally, the section headings herein are provided for consistency with the suggestions under 37 C.F.R. 1.77 or otherwise to provide organizational cues. These headings shall not limit or characterize the invention(s) set out in any claims that may issue from this disclosure. Specifically and by way of example, although the headings may refer to a “Technical Field,” such claims should not be limited by the language chosen under this heading to describe the so-called technical field. Further, a description of a technology in the “Background” is not to be construed as an admission that technology is prior art to any invention(s) in this disclosure. Neither is the “Summary” to be considered as a characterization of the invention(s) set forth in issued claims. Furthermore, any reference in this disclosure to “invention” in the singular should not be used to argue that there is only a single point of novelty in this disclosure. Multiple inventions may be set forth according to the limitations of the multiple claims issuing from this disclosure, and such claims accordingly define the invention(s), and their equivalents, that are protected thereby. In all instances, the scope of such claims shall be considered on their own merits in light of this disclosure, but should not be constrained by the headings herein.
The present application is a non-provisional patent application from and claims priority to U.S. Provisional Patent Application No. 63/312,922, the contents of which are incorporated herein in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63312922 | Feb 2022 | US |
