AU2011201569A1 - Pipette reading device - Google Patents

Pipette reading device Download PDF

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Publication number
AU2011201569A1
AU2011201569A1 AU2011201569A AU2011201569A AU2011201569A1 AU 2011201569 A1 AU2011201569 A1 AU 2011201569A1 AU 2011201569 A AU2011201569 A AU 2011201569A AU 2011201569 A AU2011201569 A AU 2011201569A AU 2011201569 A1 AU2011201569 A1 AU 2011201569A1
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AU
Australia
Prior art keywords
pipette
reading
distinctive feature
graduation
fluid
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
AU2011201569A
Inventor
Miles Blackwood
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from AU2010901463A external-priority patent/AU2010901463A0/en
Application filed by Individual filed Critical Individual
Priority to AU2011201569A priority Critical patent/AU2011201569A1/en
Publication of AU2011201569A1 publication Critical patent/AU2011201569A1/en
Abandoned legal-status Critical Current

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Abstract

A pipetting device provided with a distinctive feature disposed as close as practicable to the interior wall of the pipette tube, which feature moves according to movement of the piston assembly, and graduation marks on the surface of the pipetter tube, wherein the distinctive feature is a line created by a washer within the seal assembly, and visible around the circumference of the seal assembly. By virtue of the provision of a distinctive feature on the piston assembly adjacent the interior wall of the pipette, the distance between the reading point and the pipette graduation is greatly reduced such that significant parallax error is eliminated. ENLARGED VIEW

Description

This invention relates to the reading of graduated laboratory pipetting devices. This invention is more particularly concerned with the way in which the fluid level is read when using a pipetting device. 5 The concave fluid surface in a pipette is called the fluid meniscus and the fluid level is measured at the very bottom of the concave surface which is at a point medial to the tube walls. The miss-aligning by the operator of the meniscus level against the graduation marks, parallax error, is one of the main causes of pipetting error. Parallax error is caused because 10 the operator takes the reading when the eye is not simultaneously perpendicular to the graduation mark and the meniscus. In other words the operator holds the pipette either too high or too low relative to their eye. Moreover the reading of the meniscus can be difficult when the fluid is of a dark colour or possesses viscosity greater than water. 15 In patent specification U.S Pat. No. 12/083 700 the liquid is separated from the seal by an air gap and the fluid level is read by determining the position of the fluid surface in relation to the graduation marks on the transparent pipette body. In regard to the method of reading the fluid 20 level, US Pat application No. 12/083,700 is the same as most laboratory pipettes. The potential for parallax error is increased the further apart the two reading points are, and it has been determined that the distance between graduation marks and the meniscus of a typical 25mL graduated pipette 25 with an outside diameter of 15mm is close to 7.5mm. It is therefore easy to misalign the meniscus, the graduation mark, and the eye when reading the fluid level. The same situation applies to all pipettes where the fluid inside the pipette is read against a mark on the exterior of the pipette, although in varying degrees according to the glass tube diameter and the 30 fluid's surface tension properties. When considering pipetting devices it is desirable that parallax error be minimized as much as practicable, and that features be provided to facilitate accurate reading of dark fluids and viscous fluids. 35 In accordance with one aspect of the present invention, a pipetting device of the general type mentioned above is characterized in that a pipetting device is provided with a distinctive feature disposed as close as practicable to the interior wall of the pipette tube, which feature moves according to movement of the piston assembly, and 40 graduation marks on the surface of the pipette tube, wherein the distinctive feature is a line created by a washer within the seal assembly, and visible around the circumference of the seal assembly. By virtue of the provision of a distinctive feature on the piston assembly adjacent the interior wall of the pipette, the distance between the reading 45 point and the pipette graduation is greatly reduced such that significant parallax error eliminated Furthermore, the distinctive feature, being on the dry side of the seal, is free from reading interference caused by opaque and coloured fluids. Also, when handling viscous fluids, the provision of a distinctive reading 1 point defines clearly the volume of fluid moved according to the distance the feature moves, so that although there may be an undetermined and variable volume of fluid retained in an air gap on the wet side of the seal, this does not affect volumetric measurement while dispensing. The 5 amount of fluid in the pipette can be read accurately without bending down or holding up the pipette to eye level for reading, which may be of great advantage when working in a restricted space such as a ventilation cabinet. 10 In another embodiment of the invention the pipette section and the distinctive reading feature may be arranged so that the user has the ability to determine the fluid volume by reading a distinctive feature adjacent graduations on the inside wall of the pipette. It will be understood that the distinctive feature is best constructed of 15 chemically resistant materials and is preferably of a highly contrasting colour so that it is easily read and identifiable in use and when instructing new users on how to read the fluid level. BRIEF DESCRIPTION OF THE DRAWINGS 20 Specific embodiments of the present invention will now be described, by way of example, with reference to the following drawings, in which:. Fig 1,is an oblique view illustrating difficulties of parallax error in pipette fluid level reading. Fig. 2 is a sectional view of an embodiment of the present invention with 25 distinctive features provided as a coloured band on the seal section of the piston assembly and incorporates a magnified section DETAILED DESCRIPTION The problem experienced when reading pipettes of the prior art are 30 demonstrated in FIG. 1.The bottom of the meniscus [1] is clearly seen in the pipette [2] and in demonstration 'A' the graduation [3] is being correctly read in relation to the eye [4]. In demonstration 'B' the user is holding the pipette [2] too high relative to the eye [4] and is therefore seeing an erroneous reading of the fluid level 35 [5].The diameter of the pipette [2] is shown as 15 mm and the distance between the bottom of the meniscus [1] on the medial line [6] and the pipette graduations [7] is shown as 7.5mm FIG. 2 Shows equipment of the present invention where red line reading point [8] is adjacent the pipette graduation lines [7] 40 provided as part of the seal section [9] of the piston assembly [10]. Various viewing angles are represented by lines [11,12,13] and demonstrate that no matter what the reading angle may be parallax error is greatly reduced over the reading method shown in FIG 1. The pipette wall [14] is typically 1 to 1.5mm in thickness and due to the proximity of 45 the red line [8] to the pipette wall [14], parallax error is negligible. Graduation mark [15] represents the most distal point reached by the red line when the nominal volume of the pipette has been fully dispensed 2
AU2011201569A 2010-04-07 2011-04-07 Pipette reading device Abandoned AU2011201569A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2011201569A AU2011201569A1 (en) 2010-04-07 2011-04-07 Pipette reading device

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
AU2010901463A AU2010901463A0 (en) 2010-04-07 Pipette reading device
AU2010901463 2010-04-07
AU2011201569A AU2011201569A1 (en) 2010-04-07 2011-04-07 Pipette reading device

Publications (1)

Publication Number Publication Date
AU2011201569A1 true AU2011201569A1 (en) 2011-10-27

Family

ID=45442234

Family Applications (1)

Application Number Title Priority Date Filing Date
AU2011201569A Abandoned AU2011201569A1 (en) 2010-04-07 2011-04-07 Pipette reading device

Country Status (1)

Country Link
AU (1) AU2011201569A1 (en)

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Legal Events

Date Code Title Description
MK1 Application lapsed section 142(2)(a) - no request for examination in relevant period