|Publication number||USRE42606 E1|
|Application number||US 12/001,750|
|Publication date||Aug 16, 2011|
|Filing date||Dec 11, 2007|
|Priority date||Jan 18, 2001|
|Also published as||DE60118028D1, DE60118028T2, EP1351767A2, EP1351767B1, US6973845, US20020092367, WO2002057016A2, WO2002057016A3|
|Publication number||001750, 12001750, US RE42606 E1, US RE42606E1, US-E1-RE42606, USRE42606 E1, USRE42606E1|
|Inventors||David W. Bell, Westley D. Peters|
|Original Assignee||Beckman Coulter, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (29), Referenced by (1), Classifications (8), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is a reissue application of U.S. Pat. No. 6,973,845, which was derived from U.S. patent application Ser. No. 09/764,691, filed on Jan. 18, 2001, which is herein incorporated by reference in its entirety for all purposes.
1. Field of the Invention
The present invention relates to an apparatus for handling chemical and biological substances, and more particularly to pipetting systems.
2. Background Information
The use of manual, semiautomatic, or automatic pipette devices for the transfer and dispensing of precise quantities of fluids in analytical systems is well known as is the use of disposable pipette tip members. Disposable tips accommodate the serial use of such pipette devices in the transfer of different fluids without carryover or contamination.
A proper seat between the pipette device and disposable tip is essential. Most pipetting systems require a proper seal to create a vacuum for receiving and dispelling samples. Additionally, many analytical processes require very small sample sizes, for example, in the range of 1 to 250 micro liters. If the seal is not air-tight, the pipette device may not pick up the precise amount of sample that the device was set to receive. Therefore, the pipette device may receive and dispel too much or too little sample which could impact the quantitative or qualitative result of the assay. Also, many samples are very expensive and are wasted by unintended oversampling. This results in premature depletion of the sample and, thus, added cost.
Commercially available pipetting devices use several techniques for picking up and discarding disposable pipette tips. Some companies use specially designed mandrels for engagement with disposable pipette tips. These mandrel ends are generally tapered or cylindrical in shape to accommodate pipette tips. Both tapered and cylindrical mandrel ends provide a good seal with the pipette tip and work well to align the tip with the mandrel. However, large insertion forces are required for insertion of the pipette tip onto the tapered or cylindrical mandrel end.
With the tapered mandrel end, the engaged portion of the pipette tip continues stretching as the pipette tip travels farther up the mandrel end which results in an exponential increase in the insertion force required as the pipette tip travels farther up the mandrel. With the cylindrical mandrel end, the engaged portion of the pipette tip is held in the stretched position as the pipette tip travels farther up the mandrel end which results in a roughly linear increase in the insertion force required as the pipette tip travels farther up the mandrel.
To accommodate the large insertion forces required with cylindrical or tapered mandrel ends for automatic pipetting devices, many systems require high-inertia instrument structures to effectively attach and shuck disposable pipette tips. These high-inertia to instrument structures tend to be large and very expensive. Therefore, it is desirable to have a pipetting device and custom molded tip design that minimizes the force necessary to attach and shuck disposable pipette tips, thereby eliminating the need for massive and expensive high-inertia instrumentation systems.
To minimize the force necessary to attach and shuck disposable pipette tips, one pipetting device uses a substantially cylindrical mandrel in conjunction with custom molded pipette tips that have molded rings which act as seals between the mandrel end and the pipette tips. This prior art pipetting device is shown in
Another problem with the pipetting device shown in
For the foregoing reasons there is a need for a low insertion force custom tip and mandrel design in which the seals are positioned on the pipettor mandrel. This will reduce the need for large and costly high-inertia instrumentation. In addition, it will reduce manufacturing costs associated with pipette tips with molded rings acting as seals since fewer will be damaged during molding.
The present invention is directed to an apparatus that satisfies the need for a low insertion force custom pipette tip and pipettor mandrel design in which the seals are positioned on the pipettor mandrel.
The pipette mandrel of the present invention is an elongated hollow metallic structure that includes a lead-in portion with a first cylindrical portion adjacent to the lead-in portion. The first cylindrical portion has a first exterior diameter with a first raised band positioned upon the first exterior diameter. Additionally, the mandrel may include a second cylindrical portion with a second exterior diameter adjacent to the first cylindrical portion. The second cylindrical portion also includes a second raised band positioned upon the second exterior diameter. Both the first and second raised bands are non-resilient and stationary, being integrated as part of the mandrel.
The pipette tip of the present invention includes a collar portion and an adjacent conical head. The conical head is the receptacle portion for receiving fluids. The collar portion is used to connect the pipette tip to the mandrel. The collar portion has an interior cylindrical wall which is defined by a first step portion having a first interior diameter. When the pipette tip is fully inserted onto the mandrel, the first raised band on the mandrel contacts the first step portion of the pipette tip. The interior cylindrical wall of the pipette tip may also have a second step portion having a second interior diameter that may contact a second raised band on the mandrel when fully inserted. Thus, the first raised band on the cylindrical portion contacts the interior wall of the pipette tip to form the first seal. Additionally, the second raised band on the cylindrical portion may contact the pipette tip to form a second seal. At a minimum, the second band is useful in aligning the pipette tip on the mandrel. Because only the seal portions of the mandrel contact the pipette tip, lower forces are required to insert the pipette tip onto the mandrel and remove the pipette tip from the mandrel. Additionally, placement of the seals on the mandrel as opposed to the pipette tips reduces manufacturing costs associated with pipette tips while adding almost no additional cost to mandrel manufacturing. Furthermore, placement of the non-resilient seals upon the mandrel provide for a consistent and reliable seal between the mandrel and the pipette tips.
These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims.
The exterior of the mandrel 30 is defined by a tapered lead in 38 on the distal end 31 of the mandrel, followed by a first band 40, a first cylindrical portion 42, a second cylindrical portion 44, and a second band 46. The diameter of the lead in 38 gradually increases from the distal end 31 up to the diameter of the first band 40. The first band 40 is a raised portion on the mandrel 30 adjacent to the lead in 38 upon the first cylindrical portion 42. The first cylindrical portion 42 is an elongated portion of the mandrel 30 extending from the first band 40. The diameter of the first band 40 is slightly larger than the diameter of the first cylindrical portion 42. On the opposite end of the first cylindrical portion 42 from the first band 40, the mandrel 30 tapers into the second cylindrical portion 44, which has a larger diameter than the first cylindrical portion 42. Like the first band 40, the second band 46 is a raised portion upon the mandrel 30. The second band 46 is positioned upon the second cylindrical portion 44 and has a diameter slightly larger than that of the second cylindrical portion 44.
Insertion of the mandrel 30 into the pipette tip 12 is now described with reference first to
The first cylindrical portion 42 of the mandrel 30 does not generally contact the interior cylindrical wall of the pipette tip 12 as the mandrel is inserted because the diameter of the first cylindrical portion is less than the interior diameter of both the second step 22 and the first step 24 of the pipette tip 12. However, there may be some incidental contact between the first cylindrical portion 42 and the first step 24, depending upon manufacturing tolerances, but this incidental contact does not contribute any significant resistance during insertion. Because only a portion of the mandrel 30, specifically the first band 40, contacts the pipette tip 12, roughly constant insertion forces are required to insert the mandrel into the tip once the first band fully engages the mandrel. This constant insertion force provides an advantage over other pipettor assemblies where a greater portion of the mandrel contacts the tip.
Final alignment occurs when the second cylindrical portion 44 and the second band 46 of the mandrel 30 enters the taper 20 and second step 22 of the pipette tip 12. As shown in
As with insertion, the forces required to remove the mandrel 30 from the tip 12 are roughly constant during removal. During removal, if a second seal has been formed between the second band 46 and the second step 22 of the pipette tip 12, contact is maintained between the second band 46 and the interior wall of the second step 22 of the pipette tip 12 until the second band clears the second step and enters the first taper portion 20 of the mouth 18 of the pipette tip. The second cylindrical portion 44 of the mandrel 30 does not continually contact the interior wall of the first taper 20 of the pipette tip 12 as the mandrel is removed because the diameter of the first taper of the pipette tip is larger than the diameter of the second cylindrical portion 44. There may be some incidental contact between the second cylindrical portion 44 and the first taper 20, but this incidental contact does not contribute any significant resistance during removal.
The first seal is maintained during removal until the first band 40 clears the first step 24 of the pipette tip 12. The first band 40 then enters the second taper 23 followed by the second step 22 of the pipette tip 12. As the first band 40 is removed from the tip 12, the first band of the mandrel 30 does not generally contact the interior wall of the second step 22 or first taper 20 since the diameters of the second step and first taper are both larger than the diameter of the first band. There may be some incidental contact between the first cylindrical portion 42 and the second step 22 or first taper 20, but this incidental contact does not contribute any significant resistance during insertion. Therefore, removal forces are similar to the roughly constant insertion forces.
Since the seals for the pipettor assembly 10 are on the mandrel and not on the interior wall of the pipette tip, greater manufacturing yields of the pipette tips can be attained. As discussed previously, a core pin which forms the interior of the pipette tip must be pulled out of the tip during manufacturing. When the seals are on the interior wall of the pipette tip as with some prior pipette tips, the core pin must be dragged across the seals in order to remove the core pin from the mold, thus increasing the likelihood of damage to the seals. In contrast, during removal of the core pin from the pipette tips of the present invention, the core pin is 1 pulled out of the pipette through portions of the pipette tip with increasingly greater diameters, thereby eliminating any drag. Thus, fewer pipette tips are damaged during manufacturing when the seals are positioned on the mandrel and not the pipette tip.
Furthermore, since the seals for the pipettor assembly 10 are on the non-resilient mandrel 30 and not on the resilient interior wall of the pipette tip 12, there is no twisting of the seals upon insertion of the tip onto the mandrel. As discussed previously, when the seals are resilient and located on the pipette tip, they may improperly twist upon insertion of the mandrel into the pipette tip and prevent proper sealing. However, the present invention avoids this problem by integrating non-resilient seals onto the mandrel. When such seals are positioned on the mandrel 30 and not the pipette tip 12, twisting of the seals upon insertion of the tip onto the mandrel is eliminated and a proper seal is consistently formed between the mandrel and the pipette tip.
Another embodiment of the present invention further improves manufacturability of the pipette tips. In this embodiment, shown in
The previously described versions of the present invention have many advantages including, but not limited to low insertion, sealing, and removal forces, and higher manufacturing yields for the custom molded pipette tips. Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.
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|Citing Patent||Filing date||Publication date||Applicant||Title|
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|International Classification||G01N1/00, B01L3/02|
|Cooperative Classification||B01L3/0275, G01N35/1016, B01L2200/025, B01L2200/0689|