Patent Grant
7188993
This invention relates generally to mixing and mass transport. In particular, the invention relates to an apparatus and method for resonant-vibratory mixing.
The mixing of fluids involves the creation of fluid motion or agitation resulting in the uniform distribution of either heterogeneous or homogeneous starting materials to form an output product. Mixing processes are called upon to effect the uniform distribution of: miscible fluids such as alcohol in water; immiscible fluids such as the emulsification of oil in water; of particulate matter such as the suspension of pigment particles in a carrier fluid; mixtures of dry materials with fluids such as sand, cement and water; thixotropic (pseudo plastic) fluids with solid particulates; the chemical ingredients of pharmaceuticals; and biological specimens, such as bacteria, while growing in a nurturing media without incurring physical damage.
Mixing may be accomplished in a variety of ways: either a rotating impeller(s) mounted onto a shaft(s) immersed in the fluid mixture agitate(s) the fluid and/or solid materials to be mixed, or a translating perforated plate does the agitation, or the vessel itself containing the materials is agitated, shaken or vibrated. Mixing may be continuous (as when a rotating impeller is used or the containing vessel is vibrated) or intermittent as when the drive mechanism starts and stops in one or several directions.
With a conventional vibrational mixer, the amplitude can be varied within very narrow limits, and the frequency is generally set at the frequency of the alternating current (AC) power source. Even when using a motor controller with frequency control, the vibrational frequency of a conventional vibrational mixer can be varied only within relatively narrow limits. Mixing at the natural resonant frequency of the mechanism is usually avoided do to the high loads and associated wear of the mechanisms.
When biological tissue is cultivated, all cells must stay suspended in the nutrient broth; that is, the cells should not settle to the bottom of the vessel in which they are cultivated. However, in agitating living cells so as to minimize sedimentation, the mechanical effect of high shear caused by the agitator should not compromise the integrity of the cells. In the case of rotating agitators, quite often the culture medium creates a turbulent vortex into which the cells are sucked. Under the turbulent vortex conditions, the cells are at greater risk of being mechanically damaged and the continuous supply of oxygen to the cells is not consistently assured.
The background art is characterized by U.S. Pat. Nos. 2,091,414; 3,162,910; 2,353,492; 2,636,719; 3,498,384; 3,583,246; 3,767,168; 4,619,532; 4,972,930; 5,979,242; 6,213,630; 6,250,792; 6,263,750; and 6,579,002; the disclosures of which patents are incorporated by reference as if fully set forth herein.
Newport et al. in U.S. Pat. No. 2,091,414 disclose an apparatus for effecting vibration. This invention is limited in that only a single-mass system is disclosed.
Behnke et al. in U.S. Pat. No. 3,162,910 disclose a apparatus for shaking out foundry flasks. This invention is limited in that only a single-mass system and a single set of springs is provided.
The present invention overcomes the limitations of U.S. Pat. Nos. 2,353,492 and 2,636,719 issued to John C. O'Connor (the “O'Conner patents”) and U.S. Pat. No. 6,213,630 issued to Olga Kossman (the “Kossman patent”). The O'Conner patents disclose devices, which provide for the vibrational compaction of dry materials and for the feeding of material via a vibratory conveyance. The Kossman patent claims electronic control of motors for the purpose of vibrational control of a compaction device.
The O'Conner patents disclose vibrational mechanisms comprised of two masses. A means of imposing a cyclical force is attached to the first mass. The second mass, which holds or includes the material to be affected, is resiliently mounted to the first. The assembly is then held by resilient members to a fixed ground position. This mechanism can be effectively tuned by proper resilient member selections to substantially reduce transmitted forces to the ground position but is limited in its ability to reduce accelerations imposed on the first mass. Accelerations on the first mass, which includes the driver inducing the cyclical forces, induce high forces which in turn lead to premature failures. To lower the failure rates of the driver, either the induced forces must be reduced or the mass of the material to be affected must be severely limited. Both cases limit the available applications of the device. Further, it is stated that the preferred operating conditions are between the first and second modes of peak vibrations. This further limit the device's effectiveness due to the additional power required to operate in this range for optimum mixing accelerations and amplitudes. If the device were to operate at one of the peek modes only enough power to overcome inherent damping of the device would be required to effect maximum acceleration and amplitude at mass two.
The Kossman patent discloses a method of controlling the driver motor or motors of a vibrational device similar to the O'Conner patent. The desclosed device lacks the ability to operate at the natural frequency peaks and also suffers from a lack of ability to limit transmitted forces to either the driver or ground positions.
Ogura in U.S. Pat. No. 3,498,384 discloses a vibratory impact device. This invention is limited in that only a two-mass system is disclosed. It is not possible to achieve high payload accelerations, force cancellation and low driver accelerations with a two-mass system.
Stahle et al. in U.S. Pat. No. 3,583,246 disclose a vibration device driven by at least one imbalance generator. This invention is limited in that only a single-mass system is disclosed.
Dupre et al. in U.S. Pat. No. 3,767,168 disclose a mechanical agitation apparatus. This invention is limited in that only a single-mass system is disclosed.
Schmidt in U.S. Pat. No. 4,619,532 discloses a shaker for paint containers. This invention is limited in that only a double-mass system is disclosed.
Davis in U.S. Pat. No. 4,972,930 discloses a dynamically adjustable rotary unbalance shaker. This invention is limited in that only a single-mass system is disclosed. Moreover, the vibratory driver is directly attached to the single mass and this mass is attached to ground by pneumatic springs. High driver accelerations are an unavoidable result of such a device.
Hobbs in U.S. Pat. No. 5,979,242 discloses a multi-level vibration test system having controllable vibration attributes. This invention is limited in that it discloses a multi-driver system with a driver attached on each of the masses in the system. No disclosure of means for achieving low driver accelerations or low transmitted forces to ground is made.
Krush et al. in U.S. Pat. No. 6,250,792 discloses an integrated vibratory adapter device. This invention is limited in that only a single-mass system is disclosed.
Maurer et al. in U.S. Pat. No. 6,263,750 disclose a device for generating directed vibrations. This invention is limited in that only a single-mass system is disclosed.
Bartick et al,. in U.S. Pat. No. 6,579,002 disclose a broad-range large-load fast-oscillating high-performance reciprocating programmable laboratory shaker. This invention is limited in that only a single-mass system is disclosed. This invention is not capable of operating in a resonant condition as it is displacement rather than vibration driven.
In summary, the background art does not teach a three-mass system having a structure that is capable of achieving low-frequencies of 0–1000 Hertz (Hz), high accelerations of 2–75 accelerations equal to that caused by gravity (g's) and large displacement amplitudes of 0.01–0.5 inches. What is needed is an apparatus and method for mixing fluids and/or solids in a manner that can be varied from maintaining the integrity of fragile molecular and biological materials in the mixing vessel to homogenizing heavy aggregate material by supplying large amounts of energy.
The purpose of the invention is to provide intimate processing, for example, mixing a plurality of fluids, e.g., intimately mixing a gas in a liquid, or a liquid in another liquid, or more than two phases. One application is the mixing and dispersion of solids in liquids, in particular hard to wet solids and small particles. Other applications include preparing emulsions for chemical and pharmaceutical applications, gasifying liquids for purification and for chemical reactions, accelerating physical and chemical reactions, and suspending fine particles in fluids. The fluids to which reference is made herein may or may not include entrained solid particles.
The present invention provides an apparatus and method for mixing materials, which apparatus and method afford exquisite control over mixing in a wide range of applications. The range of applications extends from heavy-duty agitation for preparation of concrete to delicate and precise mixing required for the preparation of pharmaceuticals and the processing of biological cultures in which living organisms must remain viable through the mixing process. In a preferred embodiment, the present invention provides a vibration mixer, driven by an electronically controllable motor or motors, adapted so as to allow virtually unlimited control of the mixing process.
In a preferred embodiment, the present invention is comprised of three masses with a cyclical linear force applied to one of the masses. The linear force applied to the first mass produces a vibratory motion which is transmitted through resilient members to a second coupling mass then to a third mass. By adding a second mass, it is possible to tune the response of the system so that transmitted forces are cancelled out. A vessel is attached to the second or third mass for the purpose of mixing two or more constituents. The three masses are coupled together with resilient members which are optimized to transfer the vast majority of the force to the mixing vessel and minimize the transmitted force to the ground and supporting structure. Minimizing the transmission of force to ground and maximizing the transmitted force to the vessel most efficiently affects work done on the vessel contents and reduces wear on the linear force transducer. Most efficient operation is achieved by operation at or near resonant frequencies of the mechanism. Levels of intensity that are nearly impossible with conventional methods of vibration mixing are attained with ease by employing the resonating system disclosed herein.
One object of preferred embodiments of the invention is to facilitate mixing of two or more liquids. Another object of preferred embodiments of the invention is to facilitate mixing of one or more liquids and one or more gases. Yet another object of preferred embodiments of the invention is to facilitate mixing of one or more liquids and one or more gases. Another object of preferred embodiments of the invention is to facilitate mixing of one or more liquids with one or more solid particles. A further object of preferred embodiments of the invention is to facilitate mixing of one or more liquids with one or more solid particles with one or more gases. Yet another object of preferred embodiments of the invention is to facilitate mixing of two or more solids. Another object of preferred embodiments of the invention is to facilitate mixing of two or more non-Newtonian materials. A further object of preferred embodiments of the invention is to facilitate mixing of one or more non-Newtonian materials with one or more solid particles.
Another object of preferred embodiments of the invention is to facilitate gasification of liquids. Yet another object of preferred embodiments of the invention is to facilitate de-gasification of liquids. Another object of preferred embodiments of the invention is to accelerate physical and chemical reactions. A further object of preferred embodiments of the invention is to accelerate heat transfer. Another object of preferred embodiments of the invention is to accelerate mass transfer. Yet another object of preferred embodiments of the invention is to suspend and distribute particles. A further object of preferred embodiments of the invention is to suspend nanoparticles distribute particles. Another object of preferred embodiments of the invention is to cause micromixing. Another object of preferred embodiments of the invention is to create Newtonian instabilities. Yet another object of preferred embodiments of the invention is to cause high rates of gas-liquid and liquid-gas mass transfer. Another object of preferred embodiments of the invention is to cause dispersion of vapor bubbles into the surface and disperse into the liquid. A further object of preferred embodiments of the invention is to cause bubbles to move downward into a liquid. Another object of preferred embodiments of the invention is to cause bubbles to be suspended in a liquid. Another object of preferred embodiments of the invention is to cause vapor to cavitate in a liquid.
Yet another object of preferred embodiments of the invention is to facilitate mixing by a selected frequency, amplitude or acceleration. Another object of preferred embodiments of the invention is to disperse fine particles in a uniform manner in a Newtonian or non-Newtonian liquid medium. A further object of preferred embodiments of the invention is to cause liquids to migrate into porous solids. Another object of preferred embodiments of the invention is to cause liquids to migrate through porous solids. Another object of preferred embodiments of the invention is to cause liquids to migrate into porous solids and leach out materials. Yet another object of preferred embodiments of the invention is reduce boundary layers that impede mass transport and heat transfer. Another object of preferred embodiments of the invention is to employ resonant operation to improve efficiency of mixing. A further object of preferred embodiments of the invention is to combine three or more masses in such a manner to provide a force-canceling mode of operation. Another object of preferred embodiments of the invention is to produce low-frequencies of 0–1000 Hertz (Hz), high accelerations of 2–75 accelerations equal to that caused by gravity (g's) and large displacement amplitudes of 0.01–0.5 inches. Yet another object of preferred embodiments of the invention is to provide a self-contained system for placing the fluids and solids to be mixed on a platform and a mechanism for securing the system to the platform. Another object of preferred embodiments of the invention is provides a means for force cancellation to the base of the device.
Another object of preferred embodiments of the invention is to reduce acceleration on the oscillator, thereby increasing bearing life and extending the useful life of the components of the device. Yet another object of preferred embodiments of the invention is to provides mechanisms for operation at the resonant frequency of the device for increased efficiency and effectiveness. Another object of preferred embodiment of the invention is to employ internal force cancellation and reduce forces transmitted to the surroundings of the device. A further object of the invention is to efficiently transfer applied forces and related accelerations to the payload mass and reduce acceleration of the oscillator. Another object of preferred embodiments of the invention is to allow for automatic and/or manual adjustment of oscillatory force during operation. Another object of preferred embodiments of the invention is provide a a three, or more, mass system where operating parameters (frequency and displacement) are less sensitive to payload mass changes and provides consistent operation in a variety of situations.
Another object of preferred embodiments of the invention is a device that has three modes of vibration and operates at the highest, thereby affording the use of more compliant springs, which reduces intrinsic damping and increases efficiency. Yet another object of preferred embodiments of the invention is to provide high mass transport of gases, liquids and nutrients to cells with low shear. Another object of the invention is to provide high mass transport of gases and waste products from cells at low shear. A further object of preferred embodiments of the invention is to provide high mass transport of gases, liquids and nutrients to and into microcarriers with low shear while causing a minimum of microcarrier collisions. Another object of preferred embodiments of the invention to provide high mass transport of gases out of and from microcarriers with low shear while causing a minimum of microcarrier collisions.
Yet another object of preferred embodiments of the invention is to provide a vibratory device that can be adjusted to produce frequencies and displacements that cause fluids (gas-liquid, gas-liquid-solid systems and combinations of these systems) in the payload vessel to develop a resonant/mixing condition that establishes high levels of gas-liquid contact, a standing acoustic wave, and axial flow patterns that result in high levels of gas-liquid mass transport and mixing. Another object of preferred embodiments of the invention is to provide a vibratory device that can be adjusted to displace a payload such as a vessel filled with a variety solids that are highly loaded, e.g., very close to theoretical density, at a frequency and amplitude that cause the material to fluidize and become highly mixed. A further object of the invention is to provide a vibratory device that can be adjusted to displace a payload, such as a vessel filled with variety of solids and liquids that are highly loaded, e.g., very close to theoretical density, at a frequency and amplitude to cause the material to fluidize and become highly mixed. Another object of preferred embodiments of the invention is to provide a vibratory device comprised of two or more masses, a substantially linear vibrator and a method of control, which allows for variable force cancellation during operation, the masses being connected by resilient members in order to transfer the forces generated by the vibrator to the vessel and wherein force cancellation is controllable such that substantially linear forces can be generated in any direction.
In a preferred embodiment, the invention is an apparatus comprising: a base assembly comprising a plurality of base legs with each adjacent pair of legs being connected by at least one leg connector assembly, each of said base legs having a bottom resilient member (e.g., spring) support and a top resilient member support attached thereto; a driver assembly, said driver assembly being movable in a first linear direction and in an opposite linear direction and said driver assembly comprising a plurality of resilient member shafts having ends, each of which resilient member shafts has a driver to payload resilient member attached to each end thereof; a plurality of motor assemblies comprising a motor having a motor shaft to which an eccentric mass is attached, each of said eccentric masses having a centroid, each of said motor assemblies being rigidly connected to said driver assembly and being adapted to rotate the centroid of its eccentric mass in a plane that is parallel to another plane in which said first direction and said opposite direction lie; a payload assembly, said payload assembly being movable in the same directions as said driver assembly and being movably connected to said driver assembly by the driver to payload springs and being movably connected to the bottom resilient member support and the top resilient member support of said base assembly by a plurality of payload to base resilient members; and a plurality of reaction mass assemblies, each reaction assembly being movable in the same directions as said driver assembly and being movably connected to said payload assembly by a plurality of reaction mass to payload resilient members and movably connected to said base assembly by a plurality of reaction mass to base resilient members; wherein each of said eccentric masses has substantially the same weight and inertial properties, and wherein the eccentric masses are rotatable at substantially the same rotational speed in opposite rotational directions and around axes that lie in the same plane and, during rotation, are operative to produce a first force on said driver assembly in said first direction and a second force on said driver assembly in said opposite direction and substantially no other forces on said driver assembly. Preferably, the apparatus of further comprises: four base legs; four resilient member shafts; four motor assemblies; and four reaction mass assemblies. Preferably, the apparatus further comprises: a controller that is operative to control the rotation of the motor shafts. Preferably, the apparatus further comprises: a mixing vessel attached to said payload assembly. Preferably, the apparatus further comprises: a motor controller that is operative to cause two of the motor shafts to rotate in a clockwise direction and two of the motor shafts to rotate in a counterclockwise direction. Preferably, apparatus of claim 5 further comprises: an accelerometer that is attached to the payload assembly or to the driver assembly, said accelerometer being operative to produce a first signal that characterizes the motion of the assembly to which it is attached. Preferably, apparatus of further comprises: a polar position transducer (e.g., a resolver) that is attached to each motor shaft, each polar position transducer being operative to produce a second signal that characterizes the absolute position of the motor shaft to which it is attached.
In another preferred embodiment, the invention is a method of mixing comprising: providing an apparatus disclosed herein; and causing the eccentric masses to rotate at substantially the same rotational speed in opposite rotational directions and around axes that lie in the same plane. In yet another preferred embodiment, the invention is a method of mixing comprising: a step for providing an apparatus disclosed herein; a step for placing a composition to be mixed in said mixing chamber; and a step for causing the eccentric masses to rotate at substantially the same rotational speed in opposite rotational directions and around axes that lie in the same plane.
In another preferred embodiment, the invention is an apparatus for agitation comprising: a base; a first movable mass, said first movable mass being movable in a first linear direction and in an opposite linear direction; two means for rotating an eccentric mass, each of said eccentric masses having a centroid, each of said means for rotating being rigidly connected to said first movable mass and being adapted to rotate its eccentric mass in a first plane that is parallel to a second plane in which said first direction and said opposite direction lie; a second movable mass, said second movable mass being movable in the same directions as said first movable mass and being movably connected to said first movable mass by a first resilient means and being movably connected to said base by a second resilient means; and a third movable mass, said third movable mass being movable in the same directions as said first movable mass and being movably connected to said second movable mass by a third resilient means and movably connected to said base by a fourth resilient means; wherein each of said eccentric masses has substantially the same weight and inertial properties, and wherein the eccentric masses are rotatable at substantially the same rotational speed in opposite rotational directions and around axes that lie in the same plane and, during rotation, are operative to produce a first force on said first movable mass in said first direction and a second force on said first movable mass in said opposite direction and substantially no other forces on said first movable mass. Preferably, the apparatus further comprises: a mixing chamber that is rigidly connected to said second movable mass. Preferably, apparatus further comprises: a mixing chamber that is rigidly connected to said third movable mass. Preferably, the apparatus further comprises: first electronic or electro-mechanical means for controlling the frequency at which said second mass or said third mass moves cyclically and/or the displacement of said second mass or third mass as it moves cyclically. Preferably, the apparatus further comprises: second electronic or electro-mechanical means for controlling the frequency at which said second mass or said first mass moves cyclically and/or the displacement of said first mass as it moves cyclically. Preferably, said resilient means have spring constants that are adjustable. Preferably, apparatus further comprises: electronic or electro-mechanical means for automatically adjusting the characteristics of said resilient means, the magnitudes of the forces and the frequency at which the forces are imposed, thereby allowing control of the frequency of vibration or displacement of a payload to provide consistent and/or controlled operation of the apparatus in a variety of situations. Preferably, at least some of the resilient means are selected from the group consisting of spiral springs, leaf springs, pneumatic springs, rubber springs, piezoelectric variable springs, and pneumatic variable springs. Preferably, the second mass comprises a plurality of additional masses, each of additional masses is connected to the third mass by an additional resilient means. Preferably, the third mass comprises a plurality of additional masses, each of additional masses is connected to the second mass by an additional resilient means.
In a further preferred embodiment, the invention is an apparatus for agitation comprising: a base; a first movable mass, said first movable mass being movable in a first linear direction and in an opposite linear direction; means for cyclically imposing forces on said first movable mass in said first direction and in said opposite direction; a second movable mass, said second movable mass being movable in the same directions as said first movable mass and being movably connected to said first movable mass by a first resilient means and being movably connected to said base by a second resilient means; and a third movable mass, said third movable mass being movable in the same directions as said first movable mass and being movably connected to said second movable mass by a third resilient means and movably connected to said base by a fourth resilient means; wherein each of said means for imposing forces is operative to produce a first force on said first movable mass in said first direction and a second force on said first movable mass in said opposite direction and substantially no other forces on said first movable mass. Preferably, the apparatus further comprises: a mixing chamber that is rigidly connected to said second movable mass. Preferably, the apparatus further comprises: a mixing chamber that is rigidly connected to said third movable mass.
In another preferred embodiment, the invention is an apparatus for agitation comprising: a base; a first movable mass, said first movable mass being movable in a first linear direction and in an opposite linear direction; a driver for cyclically imposing a force on said first movable mass in said first direction or in said opposite direction; a second movable mass, said second movable mass being movable in the same directions as said first movable mass and being movably connected to said first movable mass by a first resilient means and being movably connected to said base by a second resilient means; and a third movable mass, said third movable mass being movable in the same directions as said first movable mass and being movably connected to said second movable mass by a third resilient means and movably connected to said base by a fourth resilient means; wherein said driver is operative to produce a first force on said first movable mass in said first direction or a second force on said first movable mass in said opposite direction and substantially no other forces on said first movable mass. Preferably, the apparatus further comprises: four or more independently adjustable and controllable drivers that can be adjusted to control the vibrating force, vibrating amplitude and/or vibrating frequency of said second mass or said third mass.
In a preferred embodiment, the invention is an apparatus for agitation comprising: a base; a first movable mass, said first movable mass being movable in a first linear direction and in an opposite linear direction; two means for rotating an eccentric mass, each of said eccentric masses having a centroid, each of said means for rotating being rigidly connected to said first movable mass and being adapted to rotate its eccentric mass in a first plane that is parallel to a second plane in which said first direction and said opposite direction lie; a second movable mass, said second movable mass being movable in the same directions as said first movable mass and being movably connected to said first movable mass by a first resilient means and being movably connected to said base by a second resilient means; and a third movable mass, said third movable mass being movable in the same directions as said first movable mass and being movably connected to said second movable mass by a third resilient means; wherein each of said eccentric masses has substantially the same weight and inertial properties, and wherein the eccentric masses are capable of rotation at substantially the same rotational speed in opposite rotational directions and around axes that lie in the same plane and, during rotation, are operative to produce a first force on said first movable mass in said first direction and a second force on said first movable mass in said opposite direction and substantially no other forces on said first movable mass. Preferably, the third movable means is connected to said base by a fourth resilient means.
In another preferred embodiment, the invention is a method of mixing comprising: cyclically imposing a first force on a first movable mass in a first linear direction and a second force on said first movable mass in an opposite linear direction relative to a base, said first movable mass being moved in said first linear direction and then in said opposite linear direction; the movement of said first movable mass causing movement of a second movable mass, said second movable mass being movable in the same directions as said first movable mass and being movably connected to said first movable mass by a first resilient means and being movably connected to said base by a second resilient means; the movement of said first movable mass or said second movable mass causing the movement of a third movable mass, said third movable mass being movable in the same directions as said first movable mass and being movably connected to said second movable mass by a third resilient means and movably connected to said base by a fourth resilient means; the movement of said second movable mass or said third movable mass causing mixing of a composition moved by the movement of said second movable mass or said third movable mass.
In yet another preferred embodiment, the invention is a method of mixing comprising: cyclically imposing a first force on a first movable mass in a first linear direction or a second force on said first movable mass in an opposite linear direction relative to a base, said first movable mass being moved in said first linear direction and then in said opposite linear direction; the movement of said first movable mass causing movement of a second movable mass, said second movable mass being movable in the same directions as said first movable mass and being movably connected to said first movable mass by a first resilient means and being movably connected to said base by a second resilient means; the movement of said first movable mass or said second movable mass causing the movement of a third movable mass, said third movable mass being movable in the same directions as said first movable mass and being movably connected to said second movable mass by a third resilient means and movably connected to said base by a fourth resilient means; the movement of said second movable mass or said third movable mass causing mixing of a composition moved by the movement of said second movable mass or said third movable mass. Preferably, the second movable mass or the third movable mass vibrates at the third harmonic and is operative to produce a force canceling effect, thereby reducing or eliminating forces transmitted to the surrounding environment and increasing mixing efficiency.
Further aspects of the invention will become apparent from consideration of the drawings and the ensuing description of preferred embodiments of the invention. A person skilled in the art will realize that other embodiments of the invention are possible and that the details of the invention can be modified in a number of respects, all without departing from the concept. Thus, the following drawings and description are to be regarded as illustrative in nature and not restrictive.
The features of the invention will be better understood by reference to the accompanying drawings which illustrate presently preferred embodiments of the invention. In the drawings:
The following reference numerals are used to indicate the parts and environment of the invention on the drawings:
Referring to
Oscillator mass 12 is rigidly connected to two oscillator drives 38 (e.g., two direct current (DC) servo motors) and is movably connected to intermediate mass 11 by means of oscillator to intermediate mass alignment struts 43 (two of them that are preferably rigidly connected to oscillator mass 12), oscillator to intermediate mass springs 25 (comprising four compliant springs), two retainers 40 and two locking nuts 41. Intermediate mass 11 is movably connected to rigid structure 37 by means of intermediate mass to ground alignment struts 53 (four of them that are preferably rigidly connected to rigid structure 37), intermediate mass to ground springs 27 (comprising eight compliant springs), four retainers 40 and four locking nuts 41. Payload 13 is movably connected to intermediate mass 11 by means of payload mass to intermediate mass struts 55 (two of them that are preferably rigidly connected to payload mass 13), payload mass to intermediate mass springs 26 (comprising four compliant springs), two retainers 41 and two locking nuts 40. One end of payload mass to intermediate mass springs 26 rests on stops 30 that are preferably rigidly connected to payload mass to intermediate mass struts 55. Payload 13 is also movably connected to rigid structure 37 by means of payload mass to ground alignment struts 39 (four of them that are preferably rigidly connected to payload 13), payload mass to ground springs 24 (comprising eight compliant springs), four retainers 40 and four locking nuts 41.
In another preferred embodiment, device 10 further comprises mixing chamber 60. Mixing chamber 60 is preferably attached to either intermediate mass 11 or payload 13. The mass that does not have mixing chamber 60 attached to it may also be divided into multiple masses, each with its own resilient member attachment means for attaching the mass to the mass that does not have mixing chamber 60 attached to it.
Referring to
In yet another preferred embodiment, additional servo motors 38 can be added to device 10 to provide for variability of the impulse force while device 10 is in operation. With the addition of two more servo motors 38 with identical eccentric masses 56, total force cancellation can be achieved. This is accomplished by setting all motor axes to be parallel to one another with two motors rotating clockwise and two motors rotating counterclockwise. Preferably, the eccentric masses 56 are selected so as to cancel out all forces at startup by setting the phase angle to 180 degrees for counter rotating pairs of motors. When the motors have reached the desired frequency of rotation, eccentric masses 56 are moved out of phase, thus creating an impulse force. The phase angle movement is accomplished by decelerating two of the motors for a fraction of a revolution and then reestablishing the selected frequency of rotation such that the eccentric masses no longer oppose each other. Deceleration of the motors is accomplished through a servo motor motion control unit.
Operation of the embodiment of present invention illustrated in
The centerline axis of each of the shafts 57 and the centroid of the attached eccentric masses 56 form a mass plane. In the course of one revolution, the initial position has the mass planes parallel to one another with the eccentrics 56 on each shaft above the motor plane defined by the two parallel motor shafts 57. At a quarter turn, the mass planes are coincident with the motor plane and the eccentric weights 56 of each of the shafts 57 are nearest each other. The centrifugal forces created by eccentric masses 56 are translated in the motor plane. This force is of the same magnitude but opposite direction for each of the shafts 57. This effectively cancels the force in the plane of the motor. At one half a revolution, the mass planes are again perpendicular to the motor plane and the eccentrics 56 are all below the motor plane. The centrifugal force acting on each of the shafts 57 is in the same direction, perpendicular to the motor plane. At three quarters of a revolution, the mass planes and the motor plane are again coincident but the eccentric masses 56 of each of the shafts 57 are oriented away from each other. Here again, the centrifugal forces created by the eccentric masses 56 are translated in the motor plane. Again, this force is of the same magnitude but opposite direction for each of the shafts 57. This effectively cancels the force in the plane of the motor. At one full revolution, the mass planes are again perpendicular to the motor plane and the eccentrics 56 are all above the motor plane. The centrifugal force acting on each of the shafts is in the same direction, perpendicular to the motor plane. The force acting perpendicular to the motor plane is translated vertically through connecting springs to intermediate mass 11. A further translation is then achieved through linear guides and springs from intermediate mass 11 to payload mass 13. The springs that comprise spring beds 24, 25, 26 and 27 are selected to optimize force transmission through intermediate mass 11 to payload mass 13 and minimize transmission to supporting structure 37 and surrounding environment.
Operation at resonance is determined when the disparity between the payload mass level of vibration and the driver mass level of vibration is maximized. This resonant condition is dependent on the selected spring/mass system. Preferably, springs characteristics and mass weights are chosen such that the resonant condition is achievable for the anticipated payload weight.
Operation at the resonant condition is not always be required to achieve the level of mixing desired. Operation near resonance provides substantial amplitude and accelerations to produce significant mixing. Desired levels of mixing are set by satisfying time requirements with dispersion requirements. To mix faster or more vigorously, amplitude is increased by operating closer to resonance. Operation is typically within 10 Hz of resonance. As the frequency approaches the resonant condition, small changes produce large results (the slope of the curve—frequency vs. amplitude—changes rapidly as the resonant condition is approached).
Mixing vessel 60 (in which materials are placed for mixing) is preferably attached to payload mass 3. Vigorous mixing is achieved when the transmitted force is converted to acceleration and displacement amplitude thrusting the mix constituents up and down producing a toroidal flow with sub-eddy currents.
In a further preferred embodiment, two more servo motors 38 are added to the mechanism shown in
In another preferred embodiment, variable resilient members are substituted for springs 24, 25, 26 and/or 27 to provide for changes to the resonant frequency. This addition also allows for a larger variability in the payload without sacrificing performance. Variable resilient members can be either mechanically or electronically controlled. Examples of such devices are air filled bellows, variable length leaf springs, coil spring wedges, piezoelectric bi-metal springs, or any other member which can be used as a resilient member which also has the capability of having its spring rate changed or otherwise affected.
Rather than mix by inducing bulk fluid flow, as is the case for impeller agitation, ResonantSonic® agitation as produced by the present invention mixes by inducing micro-scale turbulence through the propagation of acoustic waves throughout the medium. It is different from ultrasonic agitation because the frequency of acoustic energy is lower and the scale of mixing is larger. Another distinct difference from ultrasonic technology is that the ResonantSonic® devices are simple, mechanically driven agitators that can be made large enough to perform industrial scale tasks at reasonable cost.
A difference between the acoustic agitation technology disclosed herein and conventional impeller agitation is the scale at which complete mixing occurs. In impeller agitation, the mixing occurs through the creation of large scale eddies which are reduced to smaller scale eddies where the energy is dissipated through viscous forces. With acoustic agitation, the mixing occurs through acoustic streaming, which is the time-independent flow of fluid induced by a sound field. It is caused by conservation of momentum dissipated by the absorption and propagation of sound in the fluid. The acoustic streaming transports “micro scale” eddies through the fluid, estimated to be on the order of 100–200 μm. Although the eddies are of a microscale, the entire reactor is well mixed in an extremely short time because the acoustic streaming causes the microscale vortices to be transmitted uniformly throughout the fluid.
Device 10 in
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Referring to
Referring to
m1a1=−k1x1−c1v1+k2(x2−x1)+k3(x3−x1)+c2(v2−v1)+c3(v3−v1)
m2a2=−k2(x2−x1)−c2(v2−v1)+F
m3a3=−k3(x3−x1)−c3(v3−v1)−k4x3−c4v3
where
There are an infinite number of solutions to the three equations of motion above which describe the motion of the three mass system of device 10. Optimization of the system is dependent upon the desired operation of the system. In general, the selection of mass and spring sizes are subject to maximizing payload amplitude, minimizing forces transmitted to ground and minimizing driver amplitude. A preferred embodiment uses spring ratios as follows; k1/k1=1, k2/k1=4.6, k3/k1=3.9, k4/k11.3, and mass ratios of; m1/m1=1, m2/m1=1.17, m3/m1=0.6. The dashpot constants are a result of natural damping in the preferred embodiment and are not actual components. Therefore, the values of dashpot constants are preferably determined by testing after an embodiment is fabricated.
Referring to
Referring to
Referring to
Referring to
In a preferred embodiment, a three mass system is tuned in such a way as to minimize the transmitted forces to ground. This is accomplished by selecting a reaction mass (mass m3) such that the forces to the ground are canceled out. From
Referring to
Referring to
Referring to
Referring to
In operation, the motor assemblies 140 of the embodiment of
Variation in the manner of mixing is accomplished using a motor controller or motion controller (not shown) to generate signals to control the frequency and amplitude of the motor assemblies 140 to produce a linear vibratory motion. In alternative embodiment, the motor may be a stepper motor, a linear motor or a direct current (DC) continuous motor. By placing a accelerometer (not shown) on payload assembly 74 and/or motor block assembly 120 to provide feedback control of the mixing motor, the characteristics of agitation in the fluid or solid can be adjusted to optimize the degree of mixing and produce a high quality mixant. In a preferred embodiment, the motor controller is Model No. 6K4, 4-Axis 6K Controller, manufactured by Parker Hannifin Corporation, Compumotor Division, Rohnert Park, Calif. In a preferred embodiment, the accelerometer is a Model No. 793, Accelerometer, manufactured by Wilcoxon Research, Gaithersburg, Md.
Control of a three mass system includes of two primary aspects. The first aspect includes control of the phase angle or relative position of each of the servo motors with respect to each other. Sensors for this are the resolvers which are attached to the shaft of each motor. These devices send an absolute position signal back to the motion controller which tracks the position error from one motor to another. In turn, the motion controller then calculates and sends a correction signal back to the motors. This keeps the motors phase angles within a tolerance which is set in the control code.
The second aspect of the control system is the setting and maintenance of a desired vibration amplitude. This is accomplished by monitoring the amplitude of the payload mass movements (m1) with an accelerometer. Signals from the accelerometer are sent to the motion controller and are compared to a value set by the operator. An error correction signal is then calculated and sent to the motors to increase or decrease their frequency and phase angle to achieve the desired amplitude.
Control of the phase angle control of the motors also has two aspects. The first aspect is to maintain motor to motor position and the second aspect is to control the magnitude of the force input to the system. Maintenance of motor to motor position is necessary so that the resultant force input to the system is oriented in a single direction. This is accomplished by controlling the position of motor pairs. The motors are paired in twos or sets such that each set has identical phase angles. The motor pairs are then set in motion such that they have equal but opposite rotational frequencies. The phase position is then controlled in a manner that sums the resultant forces from the eccentric masses in a singular direction which is parallel to the orientation of the spring axes. Force magnitude is controlled by the controlling the phase angle between motor pairs. If the motor pairs are 180 degrees out of phase with each other, the net resultant force is zero. When the phase angle between motor pairs is zero degrees, the net resultant force is 100 percent of the summation of the four eccentric masses. Phase angles between these extremes result in forces that are lower than the maximum.
In summary, applicants have discovered systems and processes for the application of acoustic energy to a reactor volume that can achieve a high level of uniformity of mixing. The micromixing that is achieved and the effects in the combinations of frequency ranges, displacement ranges and acceleration ranges disclosed herein produce very high-quality mixants. The method disclosed herein can be practiced with the preferred systems disclosed herein and with single mass vibrators, dual mass vibrators, and piezoelectric and magnetostrictive transducers.
Liquid to liquid mixing is enhanced when a composition that comprises a plurality of liquids is exposed a vibratory environment that is preferably operative to vibration the composition at a frequency between about 15 Hz to about 1,000 Hz with an amplitude between about 0.02 inch to about 0.5 inch. Liquids that are not miscible are readily mixed when subjected to this condition. Normal boundary layers which prevent mixing are broken and the liquids are freely and evenly distributed with each other. Micromixing with generation of 10 micron to 100 micron droplets is achieved in this vibratory environment. The uniformity of droplet size and distribution is enhanced by this vibratory process thereby achieving greater mass transport, but the mixture is easily separated when the vibratory agitation is removed. Tuning the process between a preferred frequency between about 15 Hz to about 1,000 Hz with a preferred amplitude between about 0.02 inch to about 0.5 inch optimizes the transfer of acoustic energy into the fluid. This energy then generates an even distribution of droplets (larger than those generated with typical related processes) which collide with each other to affect mass transfer from one droplet to another. After the acoustic energy is removed, the liquids easily and quickly separate thus effecting high mass transfer without creating an emulsion.
Mixing of a composition comprising a liquid, a gas and a solid is enhanced when it occurs in a vibratory environment that is operative to vibrate the composition at a preferred frequency between about 15 Hz to about 1,000 Hz with a preferred amplitude between about 0.02 inch to about 0.5 inch. Fluids (gas-liquid, gas-liquid-solid systems and multiples of these systems) in the payload vessel are caused to develop a resonant/mixing condition that establishes high levels of gas-liquid contact, an acoustic wave, and axial flow patterns that result in high levels of gas-liquid mass transport and mixing.
Non-Newtonian or thixotropic (pseudo plastic) fluids are typically difficult to mix. By placing a composition comprising these fluids in a vibratory environment that is operative to vibrate the composition at a preferred frequency between about 15 Hz to 1,000 Hz with a preferred amplitude between 0.02 inch to 0.5 inch they become fluidized and readily mix. Under these conditions, it is possible to mix such fluids containing one or more solids, one or more gases and one or more liquids.
Mixing of a composition comprising a liquid and a gas is enhanced when it occurs in a vibratory environment that is operative to vibrate the composition at a preferred frequency between about 15 Hz to 1,000 Hz with a preferred amplitude between about 0.02 inch to about 0.5 inch to produce a gasified media. Boundary layers are easily broken and gas is entrained into the fluid. Micro sized bubbles are trapped in the fluid for extended periods of time. This process is particularly effective for the gasification of liquids used to supply gasses to bioreactors. Small bubbles subjected to the acoustic energy produce “bubble pumping.” This is the effect of compressing and expanding a bubble trapped in the fluid by acoustic energy. This instability causes the bubbles to be completely engulfed by the fluid at preferred operating conditions. The mass transfer of gas trapped in the bubbles to the liquid is also affected by the increased pressure on the bubble as the acoustic waves pass through the liquid. Henery's law states that the mass transfer of gas to liquid is proportional to the gas pressure in the bubble. This effect is dependent on the head space or volume of gas in relation to the volume of fluid in the mixing vessel. A relatively small volume of gas will produce very small bubbles with higher gas bubble pressure and retention of the bubbles is achieved for longer periods of time after the acoustic agitation is removed.
Mixing in order to remove a gas from a composition comprising a liquid and a gas (degasification) is enhanced when the composition is exposed to a vibratory environment that is operative to vibrate the composition at a lower preferred frequency of about 10 Hz to about 100 Hz and a preferred displacement of less than about 0.025 inch. Reducing the displacement and frequency to these lower levels is particularly useful in driving out entrained gas in fluids. These conditions are effective for both light fluids, such as water, and for highly viscous and solids-loaded fluids.
Physical reactions such as heat transfer, mass transfer and suspension of particles are greatly accelerated by exposing the reactants to a vibratory environment that is operative to vibrate the reactants at a preferred frequency between about 15 Hz to about 1,000 Hz with a preferred amplitude between about 0.02 inch to about 0.5 inch. By placing media containing the reactants in such an environment, the physical forces that generate these reactions are driven at higher rates. Similarly, chemical reactions are increased in rate due to enhanced contact and micro-mixing. The increased rate of media contact and breaking or reduction of boundary layers drives the reactions to occur at increased rates.
Intrusion or infusion of liquids or gases entrained in liquids into a porous solid media is enhanced by placing the porous media in an environment that is operative to vibrate the porous media at a preferred frequency of about 5 Hz to about 1,000 Hz with a preferred amplitude between about 0.02 inch to about 0.5 inch. Boundary layers are broken and fluids and gases are forced into, out of and through the porous structure.
Low shear mixing applications are necessary to prevent damage to biological cultures to reduce damage to the media. This is achieved by placing the cultures in a vibratory environment that is operative to vibrate the cultures at a preferred frequency of about 5 Hz to about 1,000 Hz with a preferred amplitude between about 0.01 inch to about 0.2 inch. The cell cultures are physically mixed with gases, solids and liquids in an environment of low shear and minimal cell to cell collisions. Nutrients and waste products are transported to and from the cell cultures with very low shear. This process also produces more conducive cell culture morphology due to the low shear. Cells are kept from agglomerating into large masses that block mass transfer to and from the individual cells.
Incorporation of a solid into a liquid is enhanced by exposing the solid and liquid to a vibratory environment that is operative to vibrate the combination at a preferred frequency between about 15 Hz to about 1,000 Hz with preferred amplitude between 0.02 inch to 0.5 inch. Incorporation can be so complete it is approaching the theoretical maximum. By placing the fluid and solids in a vibratory environment and, as a result, providing acoustic energy to the media, the effect is to fluidize the mixture. In the process, micro-mixing is accomplished throughout the vessel while macro-mixing the product. Complete and thorough mixing is accomplished by the use of acoustic energy at previously unachievable solids loadings.
Similar to liquids mixing, solids are mixed by adding acoustic energy so that micromixing is achieved. A vibratory environment operating at a preferred frequency between about 15 Hz to about 1,000 Hz with a preferred amplitude between about 0.02 inch to about 0.5 inch provides the necessary acoustic energy required to mix solids. The size of the solids can be nano-sized to much larger particles. The acoustic energy provided to the particles directly acts on the media to produce mixing. Other processes use components such as propellers to produce fluid motion through eddies which then mix the media. These eddies are dampened by the media and thus the mixing is localized near the component creating them. Acoustic energy supplied to the media is not subject to the localization of input because the entire mixing vessel volume is subject to the energy at the same time.
Many variations of the invention will occur to those skilled in the art. Some variations include embodiments wherein the oscillator mass is connected to the intermediate mass by springs and the intermediate mass is connected to the payload mass by springs. Other variations call for embodiments wherein the oscillator mass is connected to the payload mass by springs and the payload mass is connected to the intermediate mass by springs. All such variations are intended to be within the scope and spirit of the invention.
Although some embodiments are shown to include certain features, the applicant(s) specifically contemplate that any feature disclosed herein may be used together or in combination with any other feature on any embodiment of the invention. It is also contemplated that any feature may be specifically excluded from any embodiment of an invention.
This application claims the benefit of U.S. Provisional Application No. 60/443,051, filed Jan. 27, 2003, the disclosure of which application is incorporated by reference as if fully set forth herein.
The U.S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of Contract No. DAAH01-00-C-R086 awarded by U.S. Army.
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