Patent Application
20180128266
Various types of pumps exist for the purpose of pumping fluids, such as liquids. Many flow cytometers use peristaltic pumps, which have many advantages. Peristaltic pumps are positive displacement pumps. The fluid being pumped only contacts the flexible tubing and is not exposed to other pump components which could possibly cause contamination of the fluid being pumped. Both highly sterile fluids, as well as chemicals, can be pumped through a peristaltic pump since the fluids only contact the flexible tubing. Peristaltic pumps are especially suited for pumping abrasives, viscous fluids, and biological fluids.
Discussed herein are various apparatuses and methods for peristaltically pumping fluids.
In one embodiment, a method of pumping a fluid through tubing that is positioned partially around the periphery of a first disk of a peristaltic pump and partially around the periphery of a second disk of the peristaltic pump is provided. The method may include orbiting one or more first rollers at two or more angular speeds around the periphery of the first disk such that the one or more first rollers may be pressed into contact with the periphery of the first disk, the tubing, or the periphery of the first disk and the tubing. The first disk may be substantially circular and may have a first radius and each first roller may travel at the same angular speed as the other first rollers. The method may further include orbiting a plurality of second rollers at a second angular speed around the entire periphery of the second disk such that the second rollers may be pressed into contact with the periphery of the second disk, the tubing, or the periphery of the second disk and the tubing. The second disk may be substantially circular and may have a second radius that is substantially the same as the first radius. The method may further include increasing the pressure of a portion of the fluid in the tubing between one first roller and one second roller by causing the one or more first rollers to orbit at a first angular speed so that the one first roller moves along and fully compresses the tubing in a first section of the periphery of the first disk, and simultaneously causing the one second roller to move along and fully compress the tubing in a first section of the periphery of the second disk. The first angular speed may be greater than the second angular speed. The method may further include moving, after increasing the pressure of the portion of the fluid, the portion of the fluid through the tubing at a constant pressure towards an output of the tubing by causing the one or more first rollers to orbit at the second angular speed while the one first roller moves along and is fully compressing the tubing in a second section of the periphery of the first disk, and simultaneously causing the one second roller to fully compress the tubing.
In some embodiments, the method may further include reducing, after increasing the pressure of the portion of the fluid and before moving the portion of the fluid through the tubing at the constant pressure towards the output of the tubing, the angular speed of the one or more first rollers from the first angular speed to the second angular speed.
In some embodiments, the method may further include reducing, after moving the portion of the fluid through a part of the tubing at a constant pressure towards the output of the tubing, the angular speed of the one or more first rollers to a third angular speed that is less than the second angular speed.
In some such embodiments, the third angular speed may be zero.
In some other such embodiments, the one or more first rollers may move at the third angular speed while each of the first rollers may be not fully compressing the tubing.
In some other such embodiments, orbiting one or more first rollers at two or more angular speeds around the periphery of the first disk may further include orbiting two or more first rollers and the method may further include increasing, after reducing the speed of the two or more first rollers to a third angular speed, the pressure of another portion of the fluid in the tubing between another first roller of the two or more first rollers and another second roller of the plurality of second rollers by causing the two or more first rollers to orbit at the first angular speed while the other first roller moves along and fully compresses the tubing in the first section of the periphery of the first disk, and by simultaneously causing the other second roller to move along and fully compress the tubing in the first section of the periphery of the second disk. In such embodiments, the first angular speed may be greater than the second angular speed during such movement.
In some further such embodiments, the method may include orbiting, after stopping the movement of the two or more first rollers and before increasing the pressure of the other portion of the fluid in the tubing between the other first roller and the other second roller, the two or more first rollers at an angular speed less than or equal to second angular speed.
In some such embodiments, orbiting one or more first rollers at two or more angular speeds around the periphery of the first disk may further include orbiting two or more first rollers and the method may further include increasing, after stopping the movement of the two or more first rollers, the pressure of another portion of the fluid in the tubing between another first roller of the two or more first rollers and another second roller of the plurality of second rollers by causing the two or more first rollers to orbit at the first angular speed while the other first roller moves along and fully compresses the tubing in a third section of the periphery of the first disk, and by simultaneously causing the other second roller to move along and fully compress the tubing in a third section of the periphery of the second disk. In such embodiments, the first angular speed may be greater than the second angular speed.
In some other such embodiments, orbiting one or more first rollers at two or more angular speeds around the periphery of the first disk may further include orbiting two or more first rollers and the method may further include increasing, after stopping the movement of the two or more first rollers, the pressure of another portion of the fluid in the tubing between another first roller of the two or more first rollers and another second roller of the plurality of second rollers by causing the two or more first rollers to orbit at a fourth angular speed while the other first roller moves along and fully compresses the tubing in the first section of the periphery of the first disk, and by simultaneously causing the other second roller to move along and fully compress the tubing in the first section of the periphery of the second disk. In such embodiments, the fourth angular speed may be different than the second angular speed and may also be greater than the second angular speed.
In some other such embodiments, orbiting one or more first rollers at two or more angular speeds around the periphery of the first disk may further include orbiting two or more first rollers and the method may further include increasing, after stopping the movement of the two or more first rollers, the pressure of another portion of the fluid in the tubing between another first roller of the two or more first rollers and another second roller of the plurality of second rollers by causing the two or more first rollers to orbit at a fifth angular speed while the other first roller moves along and fully compresses the tubing in a fourth section of the periphery of the first disk, and by simultaneously causing the other second roller to move along and fully compress the tubing in a fourth section of the periphery of the second disk. In such embodiments, the fifth angular speed may be different than the first angular speed and may also be greater than the second angular speed.
In some embodiments, increasing the pressure of the portion of the fluid in the tubing between the one first roller and the one second roller may account for air bubbles in the tubing between the one first roller and the one second roller.
In some such embodiments, the method may further include identifying intervals with a heightened probability of having air bubbles in the tubing.
In some embodiments, moving the portion of the fluid through the tubing at a constant pressure towards an output of the tubing may further include causing, after the one first roller has moved along the second section of the periphery of the first disk, the one first roller to move along a third section of the periphery of the first disk, the one first roller to fully compress the tubing at at least the beginning of the third section of the periphery of the first disk, and the one first roller to not fully compress the tubing at at least the end of the third section of the periphery of the first disk; and causing another second roller of the plurality of second rollers to fully compress the tubing against the second disk before causing the one first roller to not fully compress the tubing at at least the end of the third section of the periphery of the first disk.
In one embodiment, a system may be provided. The system may include a first disk that may be substantially circular, may have a nominal radius, and may include a first recess in the periphery of the first disk, the first recess configured to receive a first portion of tubing for conveying fluid; a second disk that may be substantially circular, may have substantially the nominal radius, and may include a second recess in the periphery of the second disk, the second recess configured to receive a second portion of the tubing; one or more first rollers that may be configured to orbit around the periphery of the first disk such that each of the one or more first rollers travels at the same angular speed as the other first rollers and that are configured to press into contact with the periphery of the first disk, the first portion of the tubing, or the periphery of the first disk and the first portion of the tubing; a first motor that may be configured to cause the one or more first rollers to orbit the periphery of the first disk at two or more angular speeds; a plurality of second rollers that may be configured to orbit around the periphery of the second disk and configured to press into contact with the periphery of the second disk, the second portion of the tubing, or the periphery of the second disk and the second portion of the tubing; a second motor that may be configured to cause the plurality of second rollers to orbit the periphery of the second disk at a constant angular speed; and a controller for controlling the system. The controller may include control logic for controlling the first motor to cause the one or more first rollers to orbit around the periphery of the first disk at a first angular speed and a second angular speed that is less than the first angular speed, controlling the second motor to cause the plurality of second rollers to orbit around the periphery of the second disk at the second angular speed, increasing the pressure of a portion of the fluid in the tubing between one first roller of the at least one first roller and one second roller of the plurality of second rollers by controlling the first motor to cause the one or more first rollers to orbit at the first angular speed so that the one first roller moves along and fully compresses the tubing through a first section of the periphery of the first disk, and by simultaneously controlling the second motor to cause the one second roller to orbit the second disk at the second angular speed and move along and fully compress the tubing in a first section of the periphery of the second disk, and moving, after increasing the pressure of the portion of the fluid, the portion of the fluid through the tubing at a constant pressure towards an output of the tubing by controlling the first motor to cause the one or more first rollers to orbit the first disk at the second angular speed while the one first roller moves along and is fully compressing the tubing in a second section of the first disk, while the one second roller is fully compressing the tubing.
In some embodiments, the controller may further include control logic for identifying intervals with a heightened probability of having air bubbles in the tubing, and increasing, by controlling the first motor to cause the first angular speed to increase, the pressure of the portion of the fluid in the tubing between the one first roller and the one second roller to account for air bubbles in the tubing between the one first roller and the one second roller.
In some such embodiments, the system may further include a sensor configured to provide data indicative of a heightened probability of air bubbles in the tubing.
In some embodiments, the controller may further include control logic for determining the location of each of the first rollers relative to the first disk and the location of each of the second rollers relative to the second disk.
In some embodiments, the controller may further include control logic for determining the pressure in the tubing from a pressure sensor that is in fluidic communication with the tubing.
In some embodiments, the controller may further include control logic for controlling the first motor to stop the movement of the one or more first rollers.
In flow cytometry equipment, peristaltic pumps are used to pump sample fluids from sample vessels or other sources and through a cuvette or into a nozzle for analysis. In a cuvette-based system, the sample stream is hydrodynamically focused within a sheath fluid so that the sample stream is a constant width as it flows through the cuvette (where it is illuminated by lasers that are focused on a particular location). In a nozzle-based system, the sample stream is also hydrodynamically focused before being jetted out of the nozzle to form a droplet stream; it is important to keep the sample stream a constant width in the nozzle context so that the timing of droplet formation remains predictable and constant. Conventional, single-stage peristaltic pumps may cause pulsations in the pumped fluid that cause the width of a hydrodynamically focused fluid stream to vary with time, thereby making the fluid flow rate non-uniform. This can cause the flow cytometry system to be less accurate, thereby negatively affecting performance.
In a peristaltic pump, it is generally desirable to have at least two rollers evenly spaced apart about the circumference of a cam or disk; these rollers may be caused to orbit the cam or disk. The tubing of the peristaltic pump may be routed around the cam or disk such that the rollers compress and release the tubing as they orbit around the cam or disk. When the tubing is compressed by a roller, the roller will cause the fluid in the tubing to be pushed ahead of the roller. The fluid behind the roller will be at a pressure generally governed by the upstream pressure of the fluid, e.g., the fluid source pressure, and the fluid ahead of the roller will be at a pressure generally governed by the downstream pressure of the fluid, e.g., the back pressure.
Generally speaking, it is always desirable in a single-cam or single-disk peristaltic pump to have at least one roller fully compressing the tubing during all stages of operation—if there are any points in time when a roller is not fully compressing the tubing, the back pressure in the system may cause the fluid to travel backwards through the pump before being driven forwards again due to the compression on the tubing caused by the next roller to fully compress the tubing.
In a single-cam or single-disk peristaltic pump, pressure pulsations in the pumped fluid may result each time the leading roller stops fully compressing the tubing—this is because the fluid that was trapped behind the roller may become fluidically united with the fluid that was pushed ahead of the roller, thereby allowing the pressures of the two portions of fluid to equalize. Since the fluid being driven ahead of the roller is typically at a higher pressure than the fluid that follows the roller, this causes the pressure in the downstream fluid to drop slightly, which causes pulsations in pressure.
Some peristaltic pumps attempt to reduce the pulsation by using three or more rollers to average out or smooth out the pulsations, but the additional rollers decrease the lifespan of the flexible tubing of the peristaltic pump thereby leading to increased maintenance costs and pump downtime. For example, the tubing will experience 50% more wear and tear with three rollers instead of two.
In view of the issue with pulsation in the flow cytometry context, a substantially constant output pressure is desirable in many flow cytometry applications. The pulsing of the output liquid from a conventional peristaltic pump may be acceptable in many instruments and other applications. However, it would be much more desirable to have a substantially constant pressure output that does not pulse in many other applications of a peristaltic pump, e.g., in flow cytometers.
While other types of pump technology may offer more uniform pumping, such as air compression pumps or syringe pumps, there may be reasons why such alternatives may be undesirable. For example, because samples in flow cytometry may be taken from small volume containers, such as a 5 milliliter tube or 96-well plate, it is more difficult and complex to use an air compression pump that utilizes a seal with such containers. Syringe pumps may also be used for flow cytometry, but such pumps are slow, have functional problems, are difficult to clean out or de-clog, and are unable to effectively draw samples of varying media and/or varying volumes.
The present inventors conceived of a new type of peristaltic pump that provides for generally constant pressure output and that eliminates most or all of the pulsative behavior of conventional peristaltic pumps discussed above. Such improved peristaltic pumps may feature two stages—one in which the fluid is intermittently pressurized to the desired output pressure, and a second in which the pressurized fluid is then moved at a constant flow rate to an output of the pump. Generally speaking, the rollers in the second stage of such a two-stage peristaltic pump may orbit around a disk or cam of the second stage at a constant angular velocity, whereas the roller or rollers of the first stage may orbit around a disk or cam of the first stage with a varying angular speed that varies so as to be faster than, slower than, and equivalent to the constant angular velocity of the rollers in the second within certain sectors of the disk or cam of the first stage. Such embodiments are discussed in more detail below.
The two-stage peristaltic pump of
Other sections of the tubing may be wrapped around a portion of the first disk, e.g., tubing 126, and around a portion of the second disk, e.g., tubing 128; an interconnect section of tubing may span between tubing 126 and 128, e.g., tubing 127 (also may be referred to as “interconnect tube,” “interconnect tubing,” or “interconnecting tubing”). For instance, the tubing of the peristaltic pump in
Referring back to
It should be noted that such orbiting of rollers (i.e., the first and the second rollers) may also be referred to herein as the rollers rotating around or about the first disk; such orbiting also means the movement of rollers around, or encircling, the periphery of a disk. Such orbiting or movement around the periphery of a disk is not intended refer to the rotation of each roller around each roller's individual pivot point, as discussed below, although the rollers may typically rotate about their own centers as they orbit the disk and roll along the periphery of the disk. Therefore, as each roller orbits around the periphery of the disk, each roller is also simultaneously rotating about its own pivot point. It is also to be understood that the term “orbit” is used herein to refer to motion that may not be a complete orbit. For example, a roller may travel at different speeds as it makes a complete orbit around a disk—in such a case, the roller, for example, may be said to orbit the disk at a first speed and then orbit the disk at a second speed. For example, the roller may orbit the disk at the first speed through an orbital arc with an included angle of 45 degrees, and may orbit the disk at the second speed through an orbital arc with an included angle of 90 degrees.
Referring back to
Because the radius of the first disk 106 is substantially circular, it has a substantially constant radius and substantially circular periphery. Accordingly, each of the first rollers travels at substantially the same angular speed and tangential speed as the other first roller(s) (e.g., within +/−5%). There may be some minor variation in tangential speed of the rollers due, for example, to shifts in roller position due to the amount of tubing compression by the rollers; generally speaking, however, the rollers will be kept at the same nominal speed. Similarly, because the radius of the second disk 112 is substantially circular, it has a substantially constant radius and substantially circular periphery and therefore, each second roller travels at substantially the same angular and tangential speed as the other second roller(s). In some embodiments, such as that in
As noted above and discussed in greater detail below, the first rollers 108, 110 orbit around the periphery of the first disk 106 at two or more angular speeds. During each such orbit, each roller is caused to contact the periphery of the first disk 106, the tubing 126, or the periphery of the first disk 106 and the tubing 126, such that in various locations around the periphery of the first disk 106 one or more of the first rollers fully compresses the tubing 126. As indicated by arrow 130 in
Additionally, as discussed below, when fluid in the tubing is trapped between a first roller and a second roller, and the rear roller, i.e., the first roller, is moving at a greater angular speed than the front roller, i.e., the second roller, the length of the tubing containing the fluid is decreased, but because the fluid is incompressible, the volume of the fluid remains constant and forces the tubing to expand to accommodate this fluid volume which in turn increases the pressure of the trapped fluid in the tubing between these two rollers. It is this process that is used by the peristaltic pump disclosed herein to increase the pressure of a fluid flowing through the pump. Additionally, if air is trapped in this volume, the compression of this air is also used to increase the pressure of the trapped fluid.
Similar to the first stage 102, the flexible tubing 128 is wrapped around a portion of the outside perimeter, i.e., the periphery, of the second disk 112. Again, as illustrated in more detail below with respect to
In some embodiments,
Similar to the first stage 102, the second rollers 114, 116 may be mounted on roller brackets and are biased against the outer periphery of the second disk 112 by springs. As the second roller support 134 rotates the second rollers 114, 116 in the clockwise direction, the second rollers 114, 116 roll along the periphery of the second disk 112 and rotate around pivot points, thereby squeezing or compressing the flexible tubing 128 at locations along the periphery of the second disk 112 where the flexible tubing 128 is exposed to the surface of the second rollers 114, 116. The fluid in tubing 128 that is in front of a second roller, i.e., located on the side of the second roller further from the tubing inlet, is pumped by the second stage 104 by the rotation of the second roller support 134 around the second disk 112 to move the second rollers 114, 116 such that the fluid moves through the flexible tubing 128 around the periphery of the second disk 112 until the fluid exits the output 138 of the tubing, which may be connected to a flow cell in a flow cytometer or a nozzle of a flow cytometer, or other fluid-receiving system. The fluid may be pumped into any device for use and does not necessarily need to be pumped into a flow cytometer. The fluid in the second stage 104 that is in front of each of the second rollers 114, 116 (e.g., being pushed by each second roller) is not subjected to a pressure increase (when the first stage pressurizes the fluid to the same pressure as the downstream pressure at the output 138 of the tubing), but is simply moved towards the output of the tubing at a constant pressure. Back pressure of the system to which the fluid is being applied assists in maintaining a substantially constant pressure of the fluid pumped from the second stage.
As noted above, the second rollers 114, 116 are biased against (i.e., constantly pressed into contact with) the periphery of the second disk 112, tubing 128, or the periphery of the second disk 112 and tubing 128, depending on the circumferential positions of the second rollers at any given time. Furthermore, because the second rollers 114, 116 move at substantially the same angular speed around the periphery of the second disk 112, the pressure of the pumped fluid (e.g., the fluid that is pushed by each second roller 114, 116 towards the output 138 of the tubing) remains substantially the same as the fluid is pushed around the second disk 112.
Moreover, fluid from intake tubing 118 is drawn into the flexible tubing 126 as the first rollers 108, 110 move in the clockwise direction and fully compress the flexible tubing 126. Fluid is thus drawn from the intake tubing 118 and is forced out of the interconnecting tubing 127 and proceeds to the second stage 104.
As indicated by the aforementioned shaded and non-shaded circles in the interior of the first disk 106, at position 140, the first roller 108 is not fully compressing the tubing 126 and transitions to fully compressing the tubing 126 at some position in the first sector 184 (i.e., some position along the section 182).
As stated above, the first rollers 108 and 110 are configured to travel simultaneously at the same angular speed such that the movement of the first roller 108 is simultaneously mirrored by the first roller 110. Therefore, as the first roller 108 moves along a section 182 of the periphery of the first disk 182 within the first sector 184 to position 142, the first roller 110 simultaneously moves along the section of the periphery of the first disk 106 within the opposing first sector 186 from position 148 to position 150 such that the first roller 110 travels substantially the same tangential distance as the first roller 108 and substantially the same tangential and angular speeds as first roller 108.
As can be seen further in
Referring to the second stage 104 of
As described above, the second rollers 114, 116 may be configured such that they both constantly orbit at the same angular speed and may be located at opposite points on the second disk 112, e.g., separated from each other by 180 degrees about the disk center. Therefore, as the second roller 114 moves along the periphery of first sector 190, the second roller 116 simultaneously moves along the periphery of an opposing first sector that mirrors the first sector 190. Accordingly, when the second roller 116 is at position 156, the second roller 114 is at position 166, and the second roller 116 then moves from position 156 to position 158 along a substantially identical section of the periphery of the second disk 112 as section 188 of the periphery of the second disk 112 and at substantially the same angular speed as the second roller 114.
Referring to the legend in
In some embodiments, the first rollers may orbit around a part of the first disk at the same angular speed as the second rollers orbit around the second disk such that the first rollers and the second rollers traverse equivalent sections of their respective disks. For example,
As fluid is drawn into the tubing 126, fluid becomes trapped between a first roller and a second roller when these rollers are fully compressing the tubing. For instance, referring to
As stated above, when the first roller 108 moves from position 140 to position 142, and after it is fully compressing the tubing 126 and is moving at the same angular speed as the second roller 114, the first roller 108 pushes (and the second roller 114 pulls at the same rate) and causes the fluid in the tubing 126 to move towards the second disk 112 without increasing the pressure of the fluid trapped between the first roller 108 and the second roller 114 as they move between these positions (i.e., 140 to 142 and 166 to 168, respectively).
In some such situations, the fluid in the tubing between a first roller fully compressing the tubing and a second roller fully compressing the tubing will not be subjected to a pressure increase. For example, referring to
The peristaltic pump disclosed herein is configured not only to pump fluid through the tubing, but also to increase the pressure of fluid within the tubing prior to moving the fluid through the second stage. For instance, the pressure of fluid trapped in between a first roller fully compressing the tubing and a second roller fully compressing the tubing may be increased by increasing the angular speed of the first rollers to an angular speed greater than the angular speed of the second rollers.
The first roller 110 moves in a substantially identical, synchronized manner in a substantially identical second sector of the first disk 106, but at a different location, as seen in
The change in angular speed of the first rollers 108, 110 may be accomplished by increasing the angular speed at which the first rollers 108, 110 orbit around the substantially circular first disk 106, such as by increasing or decreasing the speed of a motor that causes the first rollers 108, 110 to orbit around the first disk 106. A separate motor may be used to drive the second rollers 114, 116 around the second disk 112 independently of the movement of the first rollers 108, 110.
Referring to the second stage 104 in
As depicted in
Furthermore, it is this difference in angular speeds between a first roller and a second roller that causes a pressure increase of the fluid that is trapped between that first roller and that second roller. As mentioned above, the peristaltic pump disclosed herein increases the pressure of a portion of fluid in the tubing between a first roller and a second roller by causing that first roller to move at a faster angular speed around the first disk than the angular speed of second roller around the second disk. Again, this pressure increase is caused by the first roller outracing the second roller, thereby decreasing the length of tubing between the two rollers that contains a fixed volume of fluid, which causes the tubing to expand in order to accommodate the fluid, and thus increases the pressure of the fluid.
For example, in
After the pressure in the tubing is increased to a desired pressure, e.g., equal to the desired output pressure, the first rollers may be slowed down to, and then moved at, the same angular speed of the second rollers in order to move the fluid through the tubing 126, the interconnect tubing 127, and tubing 128 towards the output 138 without further increasing the pressure. The first rollers may also be slowed down before the desired pressure is reached, e.g., such that the desired output pressure is reached near-simultaneously or simultaneously with the first rollers reaching an angular speed that matches that of the second rollers.
The first roller 110 moves in a substantially identical, synchronized manner in a substantially identical sector of the first disk 106, but at a different location, as seen in
Referring to the second stage 104 in
The deceleration rate of the first rollers 108, 110 from their angular speed in the second sector 194 to the angular speed of the second rollers 114, 116 dictates the length of the section 198 of the periphery of the first disk that the first rollers 108, 110 travel in this third sector 1100. In some embodiments, this deceleration speed is variable. For instance, in some such embodiments, this deceleration speed may be low such that the length of the section 198 that the first roller 108 travels is greater than the length of the section 1102 that the second roller 114 travels, such as depicted in
In some embodiments, this deceleration may occur very quickly, such as near-instantaneously, such that the distance traveled by the first roller is very small compared to the other sections of the periphery of the first disk it travels. In some embodiments, this distance may be negligible or non-existent. Therefore, in some such embodiments, it may be considered that this third sector is, in effect, a single point on the periphery of the first disk.
Once the angular speed of the first rollers is decelerated to match the angular speed of the second rollers, the first and the second rollers may continue around the first and second disks, respectively, at substantially the same angular speed.
As indicated by the shaded and non-shaded circles in the interior of the first disk 106, at position 146 the first roller 108 is fully compressing the tubing 126 and transitions to not fully compressing the tubing 126 at some position in the fourth sector 1108 (i.e., some position along the section disk 1106 of the periphery of the first) such that the first roller 108 is not fully compressing the tubing 126 at position 148, i.e., at the end of the sector. Because of the synchronized movement of the first rollers 108, 110, when the first roller 108 is at position 148, the first roller 110 is at position 140 and both the first rollers 108, 110 are not fully compressing tubing 126 at these positions.
In the second stage 104 in
The second roller 114 can also be seen moving along a section 1114 of the periphery of the second disk 112 within an opposing fourth sector 1116 of the second disk 112, i.e., from position 172 to position 174 of the second disk 112. In the opposing fourth sector 1116, at position 172 the second roller 116 is fully compressing the tubing 128 and transitions to not fully compressing the tubing 128 at some position in the opposing fourth sector 1116 (i.e., some position along the section 1114 of the periphery of the second disk) such that the second roller 114 is not fully compressing the tubing 128 at position 174, i.e., at the end of the sector.
As the first rollers and the second rollers move between the positions depicted in
This “handoff” is explained in more detail in
In
In
Once the second roller 116 is fully compressing tubing 128 and the second roller 114 is not fully compressing tubing 128, as seen in
After the handoff occurs between the first stage 102 and the second stage 104, both the first rollers 108, 110 may not be fully compressing the tubing 126 and may slow or stop their movement.
In some embodiments, the first rollers may be not stopped, but rather may be moving at an angular speed less than that of the second rollers, thereby moving through corresponding fifth sectors of the first disk. In such embodiments, the first rollers may still be not fully compressing the tubing 126. The non-movement or very slow angular movement of the first rollers in this interval allows the second rollers to “catch up” to the positions that the second rollers were in when the pumping cycle started, as shown in
Based on the above-described movement of the first rollers 108, 110 and the second rollers 114, 116, the first rollers 108, 110 rotate around some parts of the first disk 106 synchronously with the second rollers 114, 116. Consequently, the rotational phase of the first rollers 108, 110 and the second rollers 114, 116 is constant in some instances and not constant in other instances.
It should also be noted that the first roller 108 continues to draw fluid through the intake tubing 118, as it rotates clockwise around the periphery of the first disk 106, i.e., from soon after position 140 through a position before position 148 when it stops fully compressing tubing 126. As noted above, once the first rollers 108, 110 are both not compressing tubing 126, the second roller that is fully compressing tubing 128 may continue to draw fluid into the intake tubing 118.
As noted above, the peristaltic pump 100 of
Beginning at the left of each chart, the first roller 108 begins at position 140, like depicted in
As noted above and seen in
Once the first roller 108 has moved to cause the pressure to increase to the desired level, the first roller then may decrease its angular speed, as described above for the third sector 1100 in
After the first roller 108 stops fully compressing the tubing 126 in the fourth sector 1108, the first roller 108 stops at position 148, like previously described in
Accordingly, first stage 102 functions to increase the pressure of the fluid that is being drawn from the intake tubing 118 by causing the first rollers 108, 110 to move faster than the second rollers 114, 116 move around the second disk 112 by increasing the angular speed of the first rollers 108, 110 during certain portions of the pumping cycle. As such, the two stage peristaltic pump is capable of pumping fluids with minimal pressure variation at the outlet, which results in little or no pulsing of the fluid at the output tubing 138. Additionally, referring back to
After the above-described movements of the first and second rollers of the peristaltic, such movements may be repeated in a similar and/or identical matter so that the pump will continue to pump the fluid at a continuous output pressure. For example, once the second rollers have traveled along the periphery of the second disk as described with respect to
For example,
Once the first and second rollers move around the periphery of the first disk and second disk, respectively, the movements of the rollers may again repeat as described with respect to
In some embodiments, the subsequent movements of the first rollers may not be identical to those previously described. For instance, after the first roller 108 has moved as previously described in
As mentioned above, the peristaltic pump disclosed herein may be configured to identify and account for air in the tubing. Air may be drawn into the tubing when the peristaltic pump is running constantly and the uptake probe of the autoloader or liquid handling device is periodically removed from the sample fluid. For example, referring back to
The air that is drawn into the tubing may be identified or estimated in various manners. For instance, the estimate of air in the tubing 126 may be based on, at least in part, each incremental movement, i.e., a “count”, of the first disk and/or the second disk of the peristaltic pump that it takes the peristaltic pump to move fluid from the uptake probe 122 to the tubing 126 and the number of counts the uptake probe is in air. For instance, an estimate may be made of a particular volume of air that is drawn through the uptake probe during the time (i.e., for the particular counts) that the probe is in the air, and another estimate may be made as to the time (i.e., the particular counts) it takes for a volume of fluid (e.g., air or liquid) to travel from the uptake probe 122 through tubing 118 and to the tubing 126. For instance, the uptake probe may be in the air for 30 counts, fluid may move from the uptake probe to the tubing 126 in 350 counts, and accordingly, the volume of air may reach the tubing 126 after about 350 counts and may continue to enter tubing 126 until about 380 counts. Such calculations may be an estimate or identification of intervals with a heightened probability of having air bubbles in the tubing, and may be used to estimate the amount of air that is present. In another example, a sensor may be used that may detect and/or measure air in the tubing.
The peristaltic pump disclosed herein may be configured to account for the presence of air bubbles in the tubing, such as in the tubing between one first roller and one second roller. This may entail estimating, detecting, and/or identifying air bubbles in the tubing and then causing the first roller to move such that it decreases the volume of the tubing that contains the trapped liquid and air in order to cause that volume of both air and liquid to have the desired pressure. For example, if only liquid is trapped in the tubing between a first roller and a second roller, then the pressure on the fluid is exerted entirely by the walls of the tubing that are stretched (as caused by the first roller's above-described movement). However, if both liquid and air are trapped in the tubing between a first roller and a second roller, then the bubble will compress somewhat, causing the tubing to expand less, thereby exerting less pressure on the liquid. To account for that, the tubing length must be further decreased so that the tubing is stretched to the same amount as without the bubble, which exerts the same pressure on the liquid in the tubing.
Although two first rollers have been discussed herein, it is to be understood that the peristaltic pump disclosed herein may be configured to function with only one first roller. In some such embodiments, the first roller may move from position 140 of the first disk 106 clockwise through position 148 in the same manner as described herein above, but may move from position 148 clockwise to position 140 in a different manner. For instance, the first roller may be moved at a high angular speed clockwise from position 148 to position 140 while not fully compressing the tubing 126 such that it may arrive at position 140 and move from position 140 when the other first roller 110 would have moved from position 140; this movement may occur during the aforementioned “park” phase and therefore replace that phase. In essence, the single first roller is configured to operate for both the first rollers 108 and 110 between positions 140 and 148.
Additionally, even though the description of the movement of the first rollers and second rollers began when the rollers were at their respective positions in
In addition to the above description, the peristaltic pump disclosed herein may also be configured to pump fluid in the reverse direction through the pump. For instance, fluid may be drawn through the outlet 138, then through tubing 128, 127, and 126, respectively, and out the inlet 118. This reverse pumping may be performed by rotating both the first rollers 108, 110 and the second rollers 114, 116 in the reverse direction, e.g., counterclockwise as depicted in the above-described Figures. In some embodiments, it may not be necessary or desired to increase the pressure of fluid pumped in this reverse direction and accordingly, the angular speeds of the first rollers 108, 110 and the second rollers 114, 116 may be substantially the same during this reverse pumping. The reverse pumping may be useful to cleaning or clearing out the pump by drawing in a rinse fluid or other cleaning fluid through the pump.
For example, the peristaltic pump 100 of
As the second roller 114 orbits the second disk, a first roller, such as first roller 108 also orbits the first disk 106 counterclockwise at substantially the same angular speed as the second roller 114 so that the pressure of the fluid in the tubing 126, 127 and 128 between these two rollers is not increased. The first roller 108 may thus simultaneously move through the fourth 1108, third 1100, second 194, and first 184 sectors of the first disk 106, respectively, while fully compressing the tubing 126, but transitioning to not fully compressing the tubing 126 towards the end of the first sector 184. This movement by the first rollers 108, 110 and the second rollers 114, 116 draws fluid into the pump through the outlet 138 and through tubing 128, 127, 126, and the outlet tubing 118, respectively.
In another example of the reverse pumping, the second rollers 114, 116 may orbit the second disk 112 counterclockwise as described directly above, but the first rollers 108, 110 may be positioned in the “park” location, i.e., positions 148 and 140, respectively, of the first disk 106 such that the tubing 126 around part of the periphery of the first disk 106 is not compressed. The first rollers 108, 110 therefore are not preventing fluid from flowing through tubing 126. Accordingly, the counterclockwise movement of the second roller 114, 116 pumps fluid through the peristaltic pump from the outlet 138, through tubing 128, 127, 126, and the outlet tubing 118, respectively.
As noted above, the periphery of each disk may have a recess (i.e., trough) that is configured to receive the tubing and configured to cause the tubing to be exposed to a roller to various degrees in order to fully compress, partially compress, or not compress, the tubing.
In some embodiments, a system may be provided that includes aspects of the peristaltic pump disclosed herein above.
The system 1500 may also include a first motor 15134 that is configured to move, i.e., orbit, the first rollers 1508, 1510 around the first disk 1506 at multiple angular speeds, including a speed of zero, and a second motor 14136 that is configured to move the second rollers 1514, 1516 around the second disk at a constant angular speed. The system 1500 may also include a first roller support arm 15138 (which may be considered part of the first stage 1502) to which the first rollers 1508, 1510 are connected such that the first motor 15134 causes the support arm 15138 to rotate which in turn causes the first rollers 1508, 1510 to move around the first disk 1506. Second stage 1506 may be similarly configured (e.g., the support arm is shown but not labeled).
The system may also include a controller 15140 configured to control the system. Controller 15140 may include one or more processors and a memory that may store instructions for controlling the one or more processors to execute various instructions, which may be collectively referred to herein as “control logic,” for causing the first and second stages to pump fluid through the tubing, such as all of the operations described herein above, like in
In some embodiments, the controller 15140 may also include control logic for identifying intervals with a heightened probability of having air bubbles in the tubing, and increasing the pressure of the portion of the fluid in the tubing between one first roller and one second roller to account for air bubbles in the tubing between the one first roller and the one second roller. The system 1500 may also include a sensor 15142 that is configured to identify, determine the existence of, and/or measure air in the tubing. For instance, sensor 15142 is located such that it may detect air bubbles in uptake tubing 1518. The controller may then be able to measure and determine the amount of air that has entered tubing 1518. As stated previously, the controller may contain control logic for controlling, at least in part, the first rollers 1508, 1510 in order to increase the pressure to account for the air that has entered the tubing 1518.
The controller may also include control logic for determining the location of each of the first rollers on the first disk and the location of each of the second rollers on the second disk, which may be an angular sensor 15144 in the first motor 15134 and an angular sensor 15146 in second motor 15136. Such angular sensors 15144, 15146 may also be located in the system 1500 in locations such that they may detect the location(s) of each of the first and second rollers.
The controller may include control logic for determining the pressure in the tubing. Such logic may be calculating the pressure based, at least in part, on speed and/or distance along the periphery of the first disk the first rollers traveled. The system 1500 may also include one or more sensors that are configured to detect pressure in the tubing. Such a pressure sensor may be placed on or within the tubing, such as interconnecting tubing 1527, for example, as seen as pressure sensor 15148 in
The controller may also be configured to receive an input from a user as to a desired output pressure of fluid flowing out of the outlet 1538 and to cause the first and second stages to move (as described herein) such that the flow pressure of fluid flowing out of the outlet 1538 substantially matches the desired output pressure that was input by the user (which may flow into a flow cytometer, nozzle, or flow cell, for instance). Accordingly, the system 1500 may include a user interface associated with controller 15140. The user interface may include a display screen, graphical software displays of the apparatus and/or process conditions, and user input devices such as pointing devices, keyboards, touch screens, microphones, etc. The controller 15140 may also be communicatively connected to the first motor 15134, the second motor 15136, and/or the sensor 15142, as illustrated by the use of dotted lines between these items.
While the examples provided herein have focused on peristaltic pumps with substantially round disks used in each stage, it is to be understood that the concepts discussed herein may also be applied to peristaltic pumps having non-round disks, e.g., oval or varying diameter disks. In such alternative embodiments, the drive motors governing the angular speeds at which the various rollers orbit their respective disks may be controlled so as to replicate the tangential speeds of the rollers relative to the disk perimeters (and thus the speeds of the rollers relative to the tubing with the fluid) discussed herein. For example, the motor driving the angular speed of the support arm for the second rollers may be controlled so that the second rollers travel around the second disk at a substantially constant tangential speed, e.g., the angular speed may increase when the second rollers are traversing a reduced-diameter portion of the second disk, and may decrease when the second rollers are traversing an increased-diameter portion of the second disk. The drive motor that controls the speed of the first rollers may be similarly controlled such that the first rollers' tangential speed relative to the tangential speed of the second rollers is in accordance with the relative tangential speeds of such rollers in the examples discussed earlier herein. Due to the fact that the pumping characteristics of the dual-stage peristaltic pumps discussed herein are ultimately controlled by the speeds at which the rollers in each stage move relative to the fluid transport tubing, it may technically be possible to arbitrarily change the mechanical configuration of the disks and “correct” out the effects of such changes in the mechanical configuration by altering the movement profiles of the drive motors so that such embodiments produce the same relative movement profiles between the rollers and the tubing as discussed above with respect to the provided examples. Such embodiments are to be understood as still falling within the scope of this disclosure.
It is to be understood that use of the term “substantially” in this application and the claims, unless otherwise indicated, refers to relationship that is within ±5% of the value specified. The term “substantially” may also be used, for instance, because there may be slight variations in speed or pressure due to manufacturing tolerances or other negligible contributing factors. For example, “substantially the same angular speed” would be within ±5% of the specified angular speed. In a further example, a pressure that substantially matches another pressure would be within ±5% of that other pressure. A substantially circular shape would be a shape that has a boundary falling that falls within an annulus with an inner and outer diameter within ±5% of the diameter of a particular true circle.
The term “each,” as used herein, may be used to refer to every member of a group of multiple objects, as well as to refer to a single-object group. For example, if “at least one object” or “one or more objects” are introduced, and then followed by a later statement such as “for each object,” “for each object of the one or more objects,” or “for each object of the at least one object,” this is meant to indicate that the description that follows such a statement is applicable to each instance of such an object—regardless of whether there is only one such object or multiple such objects. This is in contrast to the standard dictionary definition for the term “each,” which implies that there must be at least two objects, but is consistent with the use of the term “each” or the phrase “for each” in computer programming and in set theory.
The foregoing description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and other modifications and variations may be possible in light of the above teachings. The embodiment was chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention except insofar as limited by the prior art.
This application is related to U.S. application Ser. No. 15/242,122, filed on Aug. 19, 2016, entitled “CONTINUOUS SAMPLE DELIVERY PERISTALTIC PUMP,” and U.S. Provisional Application No. 62/208,465, filed on Aug. 21, 2015, entitled “CONTINUOUS SAMPLE DELIVERY PERISTALTIC PUMP,” both of which are incorporated by reference herein in their entirety.
