Patent Description:
The invention relates generally to liquid chromatography systems. More particularly, the invention relates to liquid chromatography pump drive systems, and associated methods of use thereof.

Chromatography is a set of techniques for separating a mixture into its constituents. In a liquid chromatography system, one or more pumps take in and delivers a mixture of liquid solvents to a sample manager, where an injected sample awaits its arrival. Liquid chromatography pump systems require drive systems for diving the pumps and injecting solvents and/or samples. Existing drive systems for liquid chromatography systems are direct drive systems - i.e. coupled directly to a rotary to linear motion converter, with or without a gearbox. Current drive systems are designed to handle very specific flow rates and pressures. These drive systems are quickly de-rated as users operate outside the ideal range (i.e. if the flow rate is increased outside the ideal range, the pressure may decrease). For example, current drive systems are outfitted with large motors to handle high end speeds and loads. However, these large motor systems suffer in flow resolution when they are run at lower speeds. Because motors run more precisely and accurately within the designed ranges, when a motor is asked to perform outside its ideal range, the precision and resolution of the flow rate and pressure output will suffer.

Thus, improved liquid chromatography systems including pump drive systems, and associated methods of use thereof, would be well received in the art.

A prior art arrangement is known from <CIT> which relates to a fluid pump containing an optical encoder to facilitate digital closed loop control. A second arrangement is known from <CIT> which relates to a method for controlling a reciprocating pump comprising two cylinders with associated pistons.

In one embodiment, a liquid chromatography solvent pump comprises: a motor; a first piston; a second piston; a variable output drive system coupling the motor to at least one of the first piston and the second piston, the variable output drive system comprising a gearbox configured to provide a non-equal ratio between an input from the motor and an output delivered to at least one of the first piston and the second piston, wherein the first piston and the second piston are configured to deliver a flow of solvent in a liquid chromatography system.

Additionally or alternatively, the first piston is a primary piston and the second piston is an accumulator piston.

Additionally or alternatively, the gearbox includes a stage of gears comprising: a sun gear; a plurality of planet gears meshed with and surrounding the sun gear and configured to revolve around the sun gear; and a ring gear meshed with and surrounding the plurality of planet gears, wherein the plurality of planet gears are configured to revolve within the ring gear.

Additionally or alternatively, the liquid chromatography solvent pump includes a carrier connecting the plurality of planet gears, wherein the motor provides an input to the sun gear, wherein the carrier comprises an output from the plurality of planet gears.

Additionally or alternatively, the carrier provides the output to at least one of the first piston and the second piston.

Additionally or alternatively, the gearbox further comprises: a fixed housing configured to engage with the ring gear to prevent rotation of the ring gear, wherein the ring gear is configured to disengage from the fixed housing to provide for free rotation of the ring gear about the fixed housing.

Additionally or alternatively, the liquid chromatography solvent pump includes a second stage of gears, the second stage of gears comprising: a second sun gear; a second plurality of planet gears meshed with and surrounding the second sun gear and configured to revolve around the second sun gear; a second ring gear meshed with and surrounding the second plurality of planet gears, wherein the second plurality of planet gears are configured to revolve within the second ring gear; and a second carrier connecting the second plurality of planet gears, wherein the carrier provides an input to the second sun gear; and wherein the second carrier provides an output to at least one of the first piston, the second piston, and a third sun gear of a third stage of gears.

Additionally or alternatively, the liquid chromatography solvent pump includes a fixed housing configured to engage with the ring gear and the second ring gear to selectively and independently prevent rotation of the ring gear and the second ring gear, wherein the ring gear and the second ring gear are each configured to selectively and independently disengage from the fixed housing to provide for selective free rotation of the ring gear and the second ring gear about the fixed housing.

Additionally or alternatively, the gearbox is configured to provide an equal ratio between an input from the motor and an output delivered to at least one of the first piston and the second piston, and wherein the equal ratio and the non-equal ratio are selectable by an operator of the liquid chromatography solvent pump.

In another embodiment, a method of pumping solvent in a liquid chromatography system, the method comprises: providing a liquid chromatography solvent pump comprising a variable output drive system coupling a motor and at least one piston, the variable output drive system comprising a gearbox configured to provide a non-equal ratio between an input from the motor and an output delivered to the at least one piston; and varying the output from an equal ratio to the non-equal ratio between the input from the motor and the output delivered to the at least one piston.

Additionally or alternatively, the method includes delivering a flow of solvent in a liquid chromatography system by the at least one piston with a flow rate determined at least partially by the output.

Additionally or alternatively, the method includes using the liquid chromatography solvent pump in an analytical liquid chromatography system; and using the liquid chromatography solvent pump in a preparative liquid chromatography system.

Additionally or alternatively, the gearbox includes a stage of gears comprising: a sun gear; a plurality of planet gears meshed with and surrounding the sun gear and configured to revolve around the sun gear; a ring gear meshed with and surrounding the plurality of planet gears, wherein the plurality of planet gears are configured to revolve within the ring gear; a carrier connecting the plurality of planet gears; and a fixed housing, the method further comprising: providing, by the motor, an input to the sun gear; and providing, by the carrier, an output by the plurality of planet gears.

Additionally or alternatively, the method includes engaging the ring gear with the fixed housing to prevent rotation of the ring gear such that a first ratio exists between the input from the motor and the output delivered to the at least one piston.

Additionally or alternatively, the method includes disengaging the ring gear with the fixed housing to provide for free rotation of the ring gear about the fixed housing such that a second ratio exists between the input from the motor and the output delivered to the at least one piston.

Additionally or alternatively, the gearbox further includes a second stage of gears, the second stage of gears comprising: a second sun gear; a second plurality of planet gears meshed with and surrounding the second sun gear and configured to revolve around the second sun gear; a second ring gear meshed with and surrounding the second plurality of planet gears, wherein the second plurality of planet gears are configured to revolve within the second ring gear; and a second carrier connecting the second plurality of planet gears, the method further comprising: providing, by the carrier, an input to the second sun gear; and providing, by the second carrier, an output to at least one of the first piston, the second piston, and a third sun gear of a third stage of gears.

Additionally or alternatively, the method includes selectively and independently engaging, with the fixed housing, the ring gear and the second ring gear to selectively and independently prevent rotation of the ring gear and the second ring gear.

Additionally or alternatively, the method includes selectively and independently disengaging, with the fixed housing, the ring gear and the second ring gear to selectively and independently allow free rotation of the ring gear and the second ring gear about the fixed housing.

In another embodiment, a liquid chromatography system comprises: a solvent delivery system, including: a pump comprising: a motor; a first piston; a second piston; and a variable output drive system coupling the motor to at least one of the first piston and the second piston, the variable output drive system comprising a gearbox configured to provide a non-equal ratio between an input from the motor and an output delivered to at least one of the first piston and the second piston, wherein the first piston and the second piston are configured to deliver a flow of solvent in a liquid chromatography system; a sample delivery system in fluidic communication with solvent delivery system; a liquid chromatography column located downstream from the solvent delivery system and the sample delivery system; and a detector located downstream from the liquid chromatography column.

The present teaching will now be described in more detail with reference to exemplary embodiments thereof as shown in the accompanying drawings. While the present teaching is described in conjunction with various embodiments and examples, it is not intended that the present teaching be limited to such embodiments. On the contrary, the present teaching encompasses various alternatives, modifications and equivalents, as will be appreciated by those of skill in the art. Those of ordinary skill having access to the teaching herein will recognize additional implementations, modifications and embodiments, as well as other fields of use, which are within the scope of the present disclosure as described herein.

The present invention relates to liquid chromatography pump drive systems, and methods of use thereof.

Disclosed herein are pump drive systems including a motor, or other device that creates a mechanical rotation on a drive system. The liquid chromatography pump drive systems described herein include a gearbox that provides for various input-to-output ratios to be achieved between the rotation of the drive system and the output that is provided to the pump(s). The gearboxes described herein include one or more planetary gear systems configured to create various input-to-output conversion ratios. A housing or other mechanism may act as a clutch or base to selectively prevent rotation of one or more components of the planetary gear system. One or more stages of planetary gear systems are contemplated to achieve varying possible input-to-output ratios. As a result of the various outputs achieved by the drive systems, embodiments of the invention described herein may allow for a single pump and pump drive system to accommodate various liquid chromatography systems utilizing various column dimensions. Further, embodiments of the invention described herein may allow for the same pump and pump drive system to accommodate both preparative and analytical chromatography techniques. The pump drive systems described herein allow for high accuracy at various drastically disparate flow rates.

<FIG> depicts a schematic view of a liquid chromatography system that includes a solvent delivery system including the solvent reservoir filter of <FIG>, in accordance with one embodiment. <FIG> shows an embodiment of a liquid chromatography system <NUM> for separating a mixture into its constituents. The liquid chromatography system <NUM> includes a solvent delivery system <NUM> in fluidic communication with a sample manager <NUM> (also called an injector or an autosampler) through tubing <NUM>. The sample manager <NUM> is in fluidic communication with a chromatographic column <NUM> and in mechanical communication with a sample organizer <NUM>. The sample organizer <NUM> may be configured to store samples and provide stored samples to the sample manager <NUM> using an automated, robotic, or other mechanical moving process. A detector <NUM> for example, a mass spectrometer, is in fluidic communication with the column <NUM> to receive the elution.

The solvent delivery system <NUM> includes a pumping system <NUM> in fluidic communication with solvent reservoirs <NUM> from which the pumping system <NUM> draws solvents (liquid) through tubing <NUM>. In the embodiment shown, the pumping system <NUM> is embodied by a low-pressure mixing gradient pumping system. In the low-pressure gradient pumping system, the mixing of solvents occurs before the pump, and the solvent delivery system <NUM> has a mixer <NUM> in fluidic communication with the solvent reservoirs <NUM> to receive various solvents in metered proportions. This mixing of solvents (mobile phase) composition that varies over time (i.e., the gradient). In other embodiments, the liquid chromatography system <NUM> may be a high-pressure mixing system.

The pumping system <NUM> is in fluidic communication with the mixer <NUM> to draw a continuous flow of gradient therefrom for delivery to the sample manager <NUM>. Examples of solvent delivery systems that can be used to implement the solvent delivery system <NUM> include, but are not limited to, the ACQUITY Binary Solvent Manager and the ACQUITY Quaternary Solvent Manager, manufactured by Waters Corp. of Milford, Mass.

The sample manager <NUM> may include an injector valve <NUM> having a sample loop <NUM>. The sample manager <NUM> may operate in one of two states: a load state and an injection state. In the load state, the position of the injector valve <NUM> is such that the sample manager loads the sample <NUM> into the sample loop <NUM>. The sample <NUM> is drawn from a vial contained by a sample vial carrier or any device configured to carry a sample vial such as a well plate, sample vial carrier, or the like. In the injection state, the position of the injector valve <NUM> changes so that the sample manager <NUM> introduces the sample in the sample loop <NUM> into the continuously flowing mobile phase from the solvent delivery system. The mobile phase thus carries the sample into the column <NUM>. In other embodiments, a flow through needle (FTN) may be utilized instead of a Fixed-Loop sample manager. Using an FTN approach, the sample may be pulled into the needle and then the needle may be moved into a seal. The valve may then be switched to make the needle in-line with the solvent delivery system.

The liquid chromatography system <NUM> may further include a data system <NUM> that is in signal communication with the solvent delivery system <NUM>, the sample manager <NUM> and/or the sample organizer <NUM>. The data system <NUM> may include a processor <NUM> and a switch <NUM> (e.g. an Ethernet switch) for handling signal communication between the solvent delivery system <NUM>, the sample manager <NUM>, and the sample organizer <NUM>, and otherwise controlling these components of the liquid chromatography system <NUM>. A host computing system <NUM> is in communication with the data system <NUM> by which a technician can download various parameters and profiles (e.g., an intake velocity profile) to the data system <NUM>.

<FIG> depicts a schematic view of the pumping system <NUM> in accordance with one embodiment. While the pumping system <NUM> of <FIG> is shown included in the liquid chromatography system <NUM> of <FIG>, the pumping system <NUM> may also be applicable to any liquid chromatography system, such as High-Performance Liquid Chromatography systems (HPLC), Ultra Performance Liquid Chromatography systems (UPLC), Ultra High Performance Liquid Chromatography systems (UHPLC) or the like. The pumping system <NUM> may be applicable to both analytical and preparative liquid chromatography systems. Due to the advantages of the structure and/or methodology described herein, the pumping system <NUM> may be capable of operating with the precision, resolutions, flow rates, and/or pressures necessary under various types of liquid chromatography systems. Thus, it is contemplated that, because of the varying output ratios, the same pumping system incorporating some or all aspects of the present disclosure may be configured to operate with both preparative and analytical liquid chromatography systems. It is further contemplated that the same pumping system incorporating some or all aspects of the present disclosure may be configured to operate with analytical liquid chromatography systems with <NUM> microliter per minute flowrates, or for smaller nano-flow or micro-flow columns having much lower flow rates of less than <NUM> microliters per minute.

The pumping system <NUM> shown includes a motor <NUM>, a variable output drive system <NUM> that includes an input <NUM> that connected to a gearbox <NUM>. The gearbox <NUM> is connected to an output <NUM> that is connected to an accumulator piston <NUM> and a primary piston <NUM>. While not shown in <FIG>, the motor <NUM> may also be encompassed by what is considered the features of the variable output drive system <NUM>. Further, the output <NUM> of the gearbox <NUM>, while shown connected to both the accumulator piston <NUM> and the primary piston <NUM>, may also be connected to only a single one or the other of the accumulator piston <NUM> or the primary piston <NUM>. For example, the gearbox <NUM> may provide an output only to the accumulator piston <NUM> while another motor (not shown) may provide power to the primary piston. The other motor may or may not include a gearbox similar or the same as the gearbox <NUM>. It is therefore contemplated that a single gearbox <NUM> may be provided for providing varying output ratios to one or the other of the accumulator piston <NUM> and the primary piston <NUM>.

The variable output drive system <NUM> may be configured to provide a non-equal ratio between the input <NUM> and the output <NUM>. The variable output drive system <NUM> may provide the output <NUM> with a plurality of output ratios relative to the input <NUM> delivered by the motor <NUM>. The variable output drive system <NUM> may be configured to first deliver a <NUM>:<NUM> ratio relative to the input <NUM> delivered by the motor <NUM>. For example, if the motor <NUM> delivers the input <NUM> at <NUM> rpm the variable output drive system <NUM> may include a setting whereby the output <NUM> is also delivered at <NUM> rpm, providing a <NUM>:<NUM> output ratio. The variable output drive system <NUM> may also be configured with one or more additional settings whereby the input <NUM> is delivered by the motor <NUM> at a less than or greater than <NUM>:<NUM> output ratio. For example, the variable output drive system <NUM> may be configurable such that the input <NUM> is delivered by the motor <NUM> at <NUM> rpm and the output <NUM> is increased or decreased by the gearbox to a greater than or less than <NUM> rpm output. For example, the output ratio may be <NUM>:<NUM> whereby the input <NUM> of <NUM> rpm delivered by the motor is converted to a <NUM> rpm output <NUM> by the gearbox <NUM>. The output ratio may be <NUM>:. <NUM> whereby the input <NUM> of <NUM> rpm delivered by the motor is converted to a <NUM> rpm output <NUM> by the gearbox <NUM>. In some embodiments, the gearbox <NUM> may be configured to provide a plurality of different output ratios other than or in addition to the <NUM>:<NUM> output ratio. In still other embodiments, the gearbox <NUM> may provide two settings: a <NUM>:<NUM> output ratio and a second ratio that is greater than or less than the <NUM>:<NUM> output ratio.

In one embodiment, the gearbox <NUM> may be configured to provide three additional output ratios in addition to the <NUM>:<NUM> ratio: <NUM>:<NUM>, <NUM>:<NUM> and <NUM>:<NUM>. These output ratios may correspond to operation of the gearbox <NUM> in liquid chromatography systems having a <NUM> millimeter diameter column, a <NUM> millimeter diameter column, and a. <NUM> millimeter diameter column, respectively. The gearbox <NUM> may provide the ability of the pumping system <NUM> to be operable on each of these three column sizes without changing the motor <NUM>. In another embodiment, the gearbox <NUM> may be configured to provide four additional output ratios in addition to the <NUM>:<NUM> ratio: <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, and <NUM>: <NUM>. These output ratios may correspond to operation of the gearbox <NUM> in liquid chromatography systems having a <NUM> millimeter diameter column, a <NUM> millimeter diameter column, a. <NUM> diameter column, and a. <NUM> diameter column, respectively. It should be understood that these are exemplary ratios, and gearboxes contemplated herein may provide for any appropriate ratios that would increase the functionality of the pump systems within which they operate. The gearbox <NUM> may provide the ability of the pumping system <NUM> to be operable on more than one of these four column sizes without changing the motor <NUM>. In various other embodiments, any output ratio may be provided by varying the number of teeth in each of the ring gear <NUM>, planetary gear system <NUM>, and sun gear <NUM>.

With the gearbox <NUM>, embodiments of the pumping system <NUM> may be configured to deliver a flow rate of fluid equal to or greater than <NUM> microliter per minute while also being configured to deliver a flow rate of fluid equal to or less than <NUM> microliter per minute in a highly accurate manner. In other embodiments, the pumping system <NUM> may be configured to deliver a flow rate of fluid equal to or greater than <NUM> microliters per minute while also being configured to deliver a flow rate of fluid equal to or less than <NUM> microliters per minute in a highly accurate manner. In still other embodiments, the pumping system <NUM> may be configured to deliver a flow rate of fluid equal to or greater than <NUM> microliters per minute while also being configured to deliver a flow rate of fluid equal to or less than <NUM> microliters per minute in a highly accurate manner. These examples are meant to be exemplary and various other working ranges are contemplated.

In one exemplary embodiment where the gearbox <NUM> provides an input-to-output ratio of <NUM>:<NUM>, the max flow provided may be <NUM> microliters per minute. At this operational flow rate, the resolution may be <NUM> nanoliters per motorstep. In another exemplary embodiment where the gearbox provides an input-to-output ratio of <NUM>:<NUM>, the max flow may be <NUM>,<NUM> microliters per minute. At this operational flow rate, the resolution may be. <NUM> nanoliters per motorstep. It should be understood that these maximum flow rates and resolutions are exemplary and that the principles of the invention may be applied to create liquid chromatography pump systems capable of providing accurate flows of various rates and resolutions. In various embodiments, the minimum flow rate may be. <NUM>% of the maximum flow rate. In other embodiments, the minimum flow rate may be <NUM>% of the maximum flow rate. In still other embodiments, the minimum flow rate may be <NUM>% of the maximum flow rate. In one example, the maximum revolutions per second of the motor <NUM> may be <NUM> or more and the minimum may be less than one. For example, the maximum revolutions per second of the motor may be <NUM> and the minimum may be. The motor <NUM> may be configured to be maintained within this working range at the various input-to-output ratios and flow rates provided by the pumping system <NUM>.

The output <NUM> is shown extending from the gearbox and is configured to convert rotational motion from the motor <NUM> and gearbox <NUM> into linear motion used to drive the accumulator <NUM> and primary pistons <NUM>. In one embodiment, the output <NUM> may be rotary motion to linear via a ball screw. In another embodiment, the output <NUM> may be a shaft with a plurality of driving cams attached thereto which integrate with the accumulator piston <NUM> and primary piston <NUM> to provide linear motion in the pistons <NUM>, <NUM>. The output <NUM> may be configured to allow for the pistons <NUM>, <NUM> to operate in tandem: when one piston fills, the other delivers. The output <NUM> and piston <NUM>, <NUM> configuration may be capable of providing a constant flow and pressure output from the pumping system <NUM>.

The primary piston <NUM> and the accumulator piston <NUM> may be configured to pump solvent fluid into the liquid chromatography system <NUM>. The primary piston <NUM> and the accumulator piston <NUM> may be configured to operate in tandem and may both be driven by the output <NUM> from the gearbox <NUM>. The primary piston <NUM> may be configured to deliver flow at the desired flow rate during the compression stroke of the primary piston <NUM>. During the intake stroke of the primary piston <NUM>, the accumulator piston <NUM> may deliver the compression stroke at double the desired flow rate. During the compression stroke of the accumulator piston <NUM>, half of the flow delivered by the accumulator piston <NUM> may be provided to the chamber of the primary piston while the other half maintains the desired flow rate. This may be configured to maintain a constant desired flow rate and pressure by the pumping system <NUM>.

While the accumulator piston <NUM> and primary piston <NUM> may be positioned in series along a fluid path, the gearbox <NUM> described herein may be applicable to two piston pumps where pistons are placed in parallel. Still further, embodiments and aspects of the gearbox <NUM> described herein may be applicable to various other fluid pump designs, both in and out of the field of liquid chromatography, along with liquid chromatography sample syringes.

<FIG> depicts a first schematic view of the gearbox <NUM> of the pumping system <NUM> in accordance with one embodiment. The gearbox <NUM> may include a housing <NUM> surrounding a ring gear <NUM>, a planet gear system <NUM>, and a sun gear <NUM>. The planet gear system <NUM> includes a plurality of separate planet gears. The planet gear system <NUM> is meshed with and surrounding the sun gear <NUM>. The planet gear system <NUM> is configured to rotate about the sun gear <NUM>. The ring gear <NUM> may be meshed with and surrounding the planet gear system <NUM> such that the planet gear system <NUM> is configured to rotate about the ring gear <NUM>. The ring gear is meshed with or otherwise attached to the housing <NUM>. The housing <NUM> is a fixed housing, preventing movement of the ring gear <NUM> when the ring gear <NUM> is meshed with the housing <NUM>.

In the embodiment shown, the input <NUM> is connected directly to the sun gear <NUM> to drive or rotate the sun gear <NUM>. The ring gear <NUM> is fixed to the housing <NUM> and therefore does not rotate. In this embodiment, the planet gear system <NUM> rotates about the sun gear <NUM> at a rate that depends on the number of teeth of the sun gear <NUM> and the ring gear <NUM> and the rotational speed of the sun gear <NUM> provided by the input <NUM> from the motor <NUM> according to the following formula: <MAT> where Ω is rotational velocity and n is the number of teeth. Thus, the output velocity of the planet gear system <NUM> may be different than the input velocity of the sun. When the input <NUM> is directly connected to the sun gear <NUM> and the output <NUM> is connected to the planetary gear system <NUM> with the ring gear <NUM> being fixed, the torque of the gearbox <NUM> may be high but the output speed may be low compared to other embodiments described hereinbelow and shown in <FIG>. This embodiment is particularly advantageous in providing high precision resolution for the output flow.

<FIG> depicts a second schematic view of the gearbox <NUM> in accordance with one embodiment. <FIG> is differentiated from the schematic view of <FIG> in that the ring gear <NUM> has been detached from the housing <NUM> and allowed to freely rotate. In this embodiment, the entirety of the ring gear <NUM>, the planet gear system <NUM> and the sun gear <NUM> may be affixed together and rotate at the rate of the input <NUM>. Thus, the rotational velocity of the output <NUM> will equal the rotational velocity of the input <NUM> creating a <NUM>:<NUM> input to output ratio. As shown by <FIG> and <FIG>, the housing <NUM> is fixed and is configured to prevent rotation of the ring gear <NUM> when the ring gear <NUM> and the housing <NUM> are meshed. The ring gear <NUM> is configured to disengage from the housing <NUM> to provide for free rotation of the ring gear <NUM> about the housing <NUM>, which remains fixed.

As shown in <FIG> and <FIG>, the output <NUM> is attached to the planet gear system <NUM>. The output <NUM> may be any carrier interface that provides rotational motion. For example, the output <NUM> may be a carrier that attaches to, or otherwise integrates with, each of the plurality of planet gears of the planet gear system <NUM>. In the case that the planet gear system <NUM> includes three planet gears, the output <NUM> may be a carrier fixture that includes three extending prongs fitting each into a center of each of the three planet gears. The base of the fixture may be configured to attach to the cam shaft of the output <NUM>. Whatever the embodiment, the output <NUM> may take the rotation of the planet gears about the sun gear <NUM> and provide this rotational motion in a manner that may be converted into the linear motion of the pistons <NUM>, <NUM>. <FIG> depicts a perspective view of the gearbox <NUM> in accordance with one embodiment. <FIG> shows a position of the gearbox <NUM> that corresponds to the schematic shown in <FIG> where the ring gear <NUM> is meshed with and fixed to the housing <NUM>. Thus, the housing <NUM> may also include inner teeth configured to mesh with the teeth of the ring gear <NUM>. In one embodiment, the inner teeth of the housing <NUM> are configured to retract into the body of the housing <NUM> to allow the ring gear <NUM> to freely rotate about the housing <NUM>. In another embodiment, the housing <NUM> and the ring gear <NUM> may move axially relative to each other to free to ring gear <NUM> from the housing <NUM>.

As shown in <FIG>, the planet gear system <NUM> includes three planet gears, a first planet gear 62a, a second planet gear 62b, and a third planet gear 62c. The planet gears 62a, 62b, 62c each include a corresponding center opening 66a, 66b, 66c which may receive a prong of the carrier or output <NUM>. As shown, the sun gear <NUM> includes only six teeth while the ring gear includes <NUM> teeth. The planet gears each include <NUM> teeth. This embodiment is exemplary, and more or less teeth for any of the sun gear <NUM>, the planet gears 62a, 62b, 62c and ring gear <NUM> are contemplated. Further, more or less than three planet gears are contemplated in other embodiments.

<FIG> depicts a schematic view of a two-stage solvent pump gearbox <NUM> in accordance with one embodiment. The two-stage solvent pump gearbox <NUM> may be similar to the gearbox <NUM> described hereinabove. However, the two-stage solvent pump gearbox <NUM> may include two separate planetary gear systems in succession rather than a single planetary gear system as shown in the gearbox <NUM>. The two-stage solvent pump gearbox <NUM> is shown including a housing <NUM>, a first ring gear <NUM>, a first planetary gear system <NUM>, and a first sun gear <NUM>. The first planet gear system <NUM> includes a first plurality of separate planet gears. The first planet gear system <NUM> is meshed with and surrounding the first sun gear <NUM>. The first planet gear system <NUM> is configured to rotate about the first sun gear <NUM>. The first ring gear <NUM> is meshed with and surrounding the first planet gear system <NUM> such that the first planet gear system <NUM> is configured to rotate about the first ring gear <NUM>. The first ring gear <NUM> is meshed with or otherwise attached to the housing <NUM>. The housing <NUM> is a fixed housing, preventing movement of the first ring gear <NUM> when the first ring gear <NUM> is meshed with the housing <NUM>.

In the embodiment shown, an input <NUM> is connected directly to the sun gear <NUM> to drive or rotate the sun gear <NUM>. The ring gear <NUM> is fixed to the housing <NUM> and therefore does not rotate. Like the gearbox <NUM>, the planet gear system <NUM> rotates about the sun gear <NUM>, the input <NUM> is directly connected to the sun gear <NUM>, and an output <NUM> is connected to the planetary gear system <NUM> with the ring gear <NUM> being fixed. Unlike the gearbox <NUM>, the output <NUM> does not drive the pistons <NUM>, <NUM>, but rather acts as an input for the second planetary gear stage.

The second planetary gear stage is shown including a second ring gear <NUM>, a second planetary gear system <NUM>, and a second sun gear <NUM>. The second planet gear system <NUM> includes a second plurality of separate planet gears. The second planet gear system <NUM> is meshed with and surrounding the second sun gear <NUM>. The second planet gear system <NUM> is configured to rotate about the second sun gear <NUM>. The second ring gear <NUM> is meshed with and surrounding the second planet gear system <NUM> such that the second planet gear system <NUM> is configured to rotate about the second ring gear <NUM>. The second ring gear <NUM> is meshed with or otherwise attached to the housing <NUM>. As shown, the output <NUM> is connected to the second planetary gear system <NUM>. This output <NUM> may be the output provided to the pistons <NUM>, <NUM>.

The housing <NUM> is a fixed housing and the second ring gear <NUM> is shown to be disconnected from the housing <NUM>. Each of the first ring gear <NUM> and the second ring gear <NUM> is configured to be selectively affixed to the housing <NUM>. The first and second ring gears <NUM>, <NUM> may each be selectively and independently attached to the fixed housing <NUM> to prevent movement and fix the first and second ring gears <NUM>, <NUM> in place. In this embodiment, the gearbox <NUM> may include four separate input to output ratios: one where both the first and second ring gears <NUM>, <NUM> are affixed to the housing <NUM>, one where both the first and second ring gears <NUM>, <NUM> are allowed to freely rotate about the housing <NUM>, one where the first ring gear <NUM> is fixed to the housing <NUM> but the second ring gear <NUM> is allowed to freely rotate about the housing <NUM>, and one where the second ring gear <NUM> is fixed to the housing but the first ring gear <NUM> is allowed to freely rotate about the housing <NUM>.

<FIG> depicts a cross sectional perspective view of the solvent pump gearbox <NUM> with the second ring gear <NUM> engaged with the housing <NUM> and the first ring gear <NUM> disengaged from the housing <NUM> in accordance with one embodiment. In this view, a portion of the second planetary gear stage removed to reveal the first planetary gear stage. While not shown, the first sun gear <NUM> of the first stage may include an interface that connects to the input <NUM> of the system and is driven from the motor. Because the first ring gear <NUM> is shown not meshed with the housing <NUM>, the rotational output of the first set of planetary gears 162a, 162b to the second stage may be the same as the rotational input provided to the first sun gear <NUM> by the input <NUM>. The output <NUM> of the first stage is connected to the second sun gear <NUM> of the second stage. While not shown, the output <NUM> may include prongs configured to be received by the openings 166a of each of the planetary gears 162a, 162b. While <FIG> shows two planetary gears 162a, 162b in the first stage, the third planetary gear is hidden behind the output <NUM>. The second planetary gear stage shown in <FIG> includes the second sun gear <NUM>. While <FIG> shows two planetary gears 172a, 172b in the second stage, the third planetary gear is removed to expose the first stage of gears. The two planetary gears each include a corresponding center opening 176a 176b which may be connected to the output <NUM> which is provided to the pistons <NUM>, <NUM>. The second ring gear <NUM> is shown meshed with the inner teeth of the housing <NUM> to affix the second ring gear <NUM> thereto. Thus, the second stage of planetary gears will provide an input-to-output ratio that is not <NUM>:<NUM> but determined by the speed of the input rotation on the second sun gear <NUM> and the teeth of the second sun gear <NUM> and the second ring gear <NUM>.

<FIG> depicts a cross sectional perspective view of the solvent pump gearbox <NUM> with the first ring gear <NUM> engaged with the housing <NUM> and the second ring gear <NUM> disengaged from the housing <NUM> in accordance with one embodiment. Like the previous <FIG>, a portion of the second planetary gear stage removed to reveal the first planetary gear stage. Unlike <FIG>, the first ring gear <NUM> is meshed with the housing <NUM>. Thus, the rotational output of the first set of planetary gears 162a, 162b to the second stage is different from the rotational input provided to the first sun gear <NUM> by the input <NUM>. The second ring gear <NUM> is shown free to rotate about the housing <NUM>. Thus, the second stage of planetary gears will provide a <NUM>:<NUM> input-to-output ratio - i.e. whatever rotation the output <NUM> provides will be the overall output <NUM> of the gearbox <NUM> in this configuration.

<FIG> depict various schematic views of solvent pump gearboxes that might be provided. With respect to these systems, various torque and speed properties may be achieved by connecting inputs and outputs to the various gear components of the planetary gear system or stage. While these variations are shown with respect to a single stage system, these variations are also applicable to multiple stage systems. <FIG> depicts a schematic view of a solvent pump gearbox <NUM> in accordance with one embodiment. The solvent pump gearbox <NUM> includes a housing <NUM>, a ring gear <NUM>, a planet gear system <NUM>, and a sun gear <NUM>. An input <NUM> provides a rotary motion input to the planetary gear system and an output <NUM> carries a rotary motion output to the pistons of the pump system (not shown). The solvent pump gearbox <NUM> may replace the solvent pump gearbox <NUM> described herein above and incorporated into the pumping system <NUM> and any type of appropriate or desired liquid chromatography system.

Unlike the gearbox <NUM>, the input <NUM> of the solvent pump gearbox <NUM> is attached or otherwise integrated into the planetary gear system <NUM>, which may include a plurality of separate planetary gears. The ring gear <NUM> is removably fixed to the housing when the system is configured to provide for a change in input-to-output gear ratio. The sun gear <NUM> is rotated by the planetary gear system <NUM> to produce the output <NUM> to the pistons. This embodiment may be particularly beneficial if output speed is to be maximized and the max output torque is to be minimized.

<FIG> depicts a schematic view of a solvent pump gearbox <NUM> in accordance with one embodiment. The solvent pump gearbox <NUM> includes a housing <NUM>, a ring gear <NUM>, a planet gear system <NUM>, and a sun gear <NUM>. An input <NUM> provides a rotary motion input to the planetary gear system and an output <NUM> carries a rotary motion output to the pistons of the pump system (not shown). The solvent pump gearbox <NUM> may replace the solvent pump gearbox <NUM> described herein above and incorporated into the pumping system <NUM> and any type of appropriate or desired liquid chromatography system.

This embodiment shows the input <NUM> and output <NUM> attached to different features of the planetary gear system. In particular, the input <NUM> in this embodiment is attached to the outer ring gear <NUM>, which is configured to rotate. The sun gear <NUM> is removably fixed the housing <NUM>. The planet gear system <NUM> is configured to rotate between the fixed sun gear <NUM> and the rotating outer ring gear <NUM> to produce the output <NUM> to the pistons. This embodiment may be particularly beneficial if minimum torque is desired to be high and minimum output speed is desired to be low.

This embodiment also shows the input <NUM> and output <NUM> attached to different features of the planetary gear system. In particular, the input <NUM> in this embodiment is attached to the planet gear system <NUM>, which is configured to rotate. The sun gear <NUM> is removably fixed the housing <NUM>. The ring gear <NUM> is configured to rotate to produce the output <NUM> to the pistons. This embodiment may be particularly beneficial if minimum speed is desired to be high and minimum torque is desired to be low.

This embodiment also shows the input <NUM> and output <NUM> attached to different features of the planetary gear system. In particular, the input <NUM> in this embodiment is attached to the sun gear <NUM>, which is configured to rotate. The planetary gear system <NUM> is removably fixed to a housing <NUM>. In this embodiment, the housing <NUM> may be configured to allow the planet gears of the planet gear system <NUM> to spin or rotate freely on a fixed and immovable axis. Thus, the housing <NUM> may prevent the rotation of the planet gears of the planet gear system <NUM> about the sun gear <NUM>. In this embodiment, the ring gear <NUM> is configured to rotate to produce the output <NUM> to the pistons. This embodiment may be particularly beneficial for low speed and high torque operating requirements.

This embodiment also shows the input <NUM> and output <NUM> attached to different features of the planetary gear system. In particular, the input <NUM> in this embodiment is attached to the ring gear <NUM>, which is configured to rotate. The planetary gear system <NUM> is removably fixed to a housing <NUM>. In this embodiment, the housing <NUM> may be configured to allow the planet gears of the planet gear system <NUM> to spin or rotate freely on a fixed and immovable axis. Thus, the housing <NUM> may prevent the rotation of the planet gears of the planet gear system <NUM> about the sun gear <NUM>. In this embodiment, the sun gear <NUM> is configured to rotate to produce the output <NUM> to the pistons. This embodiment may be particularly beneficial for high speed and low torque operating requirements.

While the above schematic embodiments shown in <FIG> depict single stage systems, embodiments of the present invention may be applied to gearboxes having two stages, three stages, four stages, five stages, six stages or the like. The larger the number of stages, the more possible input-to-output gear ratios may be provided by the gearbox. This may be particularly advantageous if, for example, a motor is used having a small optimum output range that needs to be running very close to the same speed to maintain resolution, precision or efficiency.

Further contemplated are methods of pumping solvent in a liquid chromatography system, such as the liquid chromatography system <NUM>, using a pumping system, such as the pumping system <NUM>. In one embodiment, a method of pumping solvent in a liquid chromatography system may include
providing a liquid chromatography solvent pump comprising a variable output drive system, such as the variable output drive system <NUM>, coupling a motor, such as the motor <NUM>, and at least one piston, such as the pistons <NUM>, <NUM>. The variable output drive system may include a gearbox, such as the gearbox <NUM>, configured to provide a non-equal ratio between an input, such as the input <NUM>, from the motor and an output, such as the output <NUM>, delivered to the at least one piston. The method may include varying the output from an equal ratio to the non-equal ratio between the input from the motor and the output delivered to the at least one piston. The method may further include delivering a flow of solvent in a liquid chromatography system by the at least one piston with a flow rate determined at least partially by the output. The method may include using the liquid chromatography solvent pump in an analytical liquid chromatography system and in a preparative liquid chromatography system. The method may include providing a first stage of planetary gears in the gearbox. The method may include providing, by the motor, an input to a sun gear of first stage of planetary gears, such as the sun gear <NUM>, <NUM>. The method may include providing an output by a carrier, such as one of the outputs <NUM>, <NUM>, <NUM>, by a plurality of planet gears, such as one of the planet gear system <NUM>, <NUM>, <NUM>.

The method may include engaging a ring gear, such as the ring gear <NUM>, <NUM>, <NUM> with a fixed housing, such as the housing <NUM>, <NUM>, to prevent rotation of the ring gear such that a first ratio exists between the input from the motor and the output delivered to the at least one piston. The method may include disengaging the ring gear with the fixed housing to provide for free rotation of the ring gear about the fixed housing such that a second ratio exists between the input from the motor and the output delivered to the at least one piston. The method may include providing a second stage of planetary gears in the gearbox. The method may include providing an input, by a second carrier, such as the output <NUM>, to a second sun gear, such as the second sun gear <NUM>. The method may include providing an output, by the second carrier, to a piston or to a third sun gear of a third stage of gears. The method may include selectively and independently engaging, with the fixed housing, the ring gear and the second ring gear to selectively and independently prevent rotation of the ring gear and the second ring gear. The method may further include selectively and independently disengaging, with the fixed housing, the ring gear and the second ring gear to selectively and independently allow free rotation of the ring gear and the second ring gear about the fixed housing.

While embodiments of the present invention have been described herein for purposes of illustration, many modifications and changes will become apparent to those skilled in the art. Accordingly, the appended claims are intended to encompass all such modifications and changes as fall within the scope of the claims.

Claim 1:
A liquid chromatography solvent pump (<NUM>) comprising:
a motor (<NUM>);
a first piston (<NUM>);
a second piston (<NUM>);
a variable output drive system (<NUM>) coupling the motor (<NUM>) to at least one of the first piston (<NUM>) and the second piston (<NUM>), the variable output drive system (<NUM>) comprising a gearbox (<NUM>) configured to provide a non-equal ratio between an input (<NUM>, <NUM>) from the motor (<NUM>) and an output (<NUM>, <NUM>) delivered to at least one of the first piston (<NUM>) and the second piston (<NUM>),
wherein the first piston (<NUM>) and the second piston (<NUM>) are configured to deliver a flow of solvent in a liquid chromatography system (<NUM>).