U.S. patent application number 09/766136 was filed with the patent office on 2002-07-25 for plate locator for precision liquid handler.
Invention is credited to Acker, Jeffrey L., Fawcett, Kevin R..
Application Number | 20020098115 09/766136 |
Document ID | / |
Family ID | 25075516 |
Filed Date | 2002-07-25 |
United States Patent
Application |
20020098115 |
Kind Code |
A1 |
Fawcett, Kevin R. ; et
al. |
July 25, 2002 |
PLATE LOCATOR FOR PRECISION LIQUID HANDLER
Abstract
A locator bed has nests where sample well containing plates are
held and positioned for accessing by probes moved by an X-Y-Z
positioning system. Each nest includes stop posts at two sides of a
rectangular base of a plate, and biasing posts at the opposed two
sides. The stop posts and the biasing posts have tapered upper
guide portions for guiding a descending plate into position and
cylindrical lower portions receiving the base of the plate in a
seated position. The stop posts are located on the surface of the
locator bed by conical seat portions. The biasing posts are placed
over studs fastened to the bed surface, and hoop springs are
captured between the studs and the biasing posts.
Inventors: |
Fawcett, Kevin R.;
(Ridgeway, WI) ; Acker, Jeffrey L.; (Middleton,
WI) |
Correspondence
Address: |
PHILIP M. KOLEHMAINEN
910 W VAN BUREN #302
CHICAGO
IL
60607
US
|
Family ID: |
25075516 |
Appl. No.: |
09/766136 |
Filed: |
January 19, 2001 |
Current U.S.
Class: |
422/63 ;
422/561 |
Current CPC
Class: |
G01N 35/0099 20130101;
G01N 2035/0425 20130101; B01L 2300/0829 20130101; B01L 9/523
20130101; C40B 60/14 20130101; G01N 35/04 20130101; G01N 35/1065
20130101; G01N 2035/0427 20130101; B01J 2219/00351 20130101; B01J
2219/00317 20130101; B01J 2219/00691 20130101 |
Class at
Publication: |
422/63 ;
422/99 |
International
Class: |
G01N 035/00 |
Claims
What is claimed is:
1. A plate locator for positioning and holding a four sided plate
having an array of sample containing wells, such as a microplate,
on a work bed of a precision liquid handler having at least one
probe for registration with at least one well of the plate, said
plate locator apparatus comprising: a flat, planar locator bed
adapted to be secured to the work bed of the precision liquid
handler; a plate receiving nest on said locator bed, said nest
having four sides corresponding to the four sides of the four sided
plate; said nest including rigid stop members extending up from
said bed on first and second sides of said nest; said nest
including movably mounted holders extending up from said bed at
third and fourth sides of said nest opposite said rigid stop
members at said first and second sides of said nest; and resilient
biasing elements connected between said bed and each of said
movably mounted holders for urging said holders toward the center
of said nest.
2. The plate locator of claim 1, wherein there are only three said
rigid stop members and only two said movably mounted holders.
3. The plate locator of claim 2, said two movably mounted holders
being located near a first corner where said third and fourth sides
intersect, and two of said three rigid stop member being located
near a second corner opposite said first corner.
4. The plate locator of claim 1, further comprising access recesses
in said bed adjacent an opposed pair of sides of said nest.
5. The plate locator of claim 1, said rigid stop members comprising
stop posts.
6. The plate locator of claim 5, said bed having a conical recess
for each of said stop posts, said stop posts being circular in
cross section throughout their lengths and each having a conical
bottom portion received in a corresponding said conical recess.
7. The plate locator of claim 1, each of said movably mounted
holders comprising a biasing post.
8. The plate locator of claim 7, further comprising a stud secured
to said bed for each said biasing post, said biasing post having a
central cavity receiving said stud.
9. The plate locator of claim 8, said resilient biasing element
comprising a spring in said cavity between said stud and said
biasing post.
10. The plate locator of claim 9, said stud and said biasing post
having circular cross sections and defining an annular spring
receiving chamber between said stud and biasing post in said
cavity, said spring being received in said annular chamber.
11. The plate locator of claim 10, said spring comprising a hoop
spring having coils surrounding a circular axis.
12. The plate locator of claim 1, said rigid stop members and said
movably mounted holders comprising posts having vertical portions
immediately adjacent said bed and having inclined plate guide
portions above said vertical portions.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to precision liquid handlers
for pharmaceutical, drug development and similar laboratory
applications, and more specifically to a plate locator for holding
and accurately positioning sample well plates in a liquid
handler.
DESCRIPTION OF THE PRIOR ART
[0002] In pharmaceutical, genomic and proteomic research and drug
development laboratories, and other biotechnology applications,
automated liquid handlers are used for handling laboratory samples
in a variety of laboratory procedures. For example, liquid handlers
are used for biotechnological and pharmaceutical liquid assay
procedures, sample preparation, compound distribution, microarray
manufacturing and the like. An automated liquid handler has a work
bed that supports an array of sample receptacles. One-piece sample
containing plates having an integral array of many sample
containing receptacles or wells are widely used. A typical liquid
handler has a probe or an array of multiple probes that are moved
into alignment with one or more wells to carry out liquid handling
operations such as adding liquid to the wells.
[0003] It is desirable to decrease the volumes of samples treated
with automated liquid handlers. Sample containing plates with a
footprint of about three and one-half by five inches and having an
X-Y array of 96 wells in an eight by twelve well pattern have been
widely used. In order to increase throughput and to reduce
consumption of sample constituents, these plates are being
superceded by microplates of the same footprint but having an array
of smaller wells, for example 384 wells in a sixteen by twenty-four
array. This trend is continuing, and there is a need for an
automated liquid handler able to accommodate microtiter plates
having a very dense array of a very large number of very small
volume wells for sample volumes in the nanoliter range. For
example, some microtiter plates presently in use have the same
footprint as previously used plates but have 1,536 wells in a
thirty-two by forty-eight well array.
[0004] Microtiter plates with a dense array of small, closely
spaced wells present serious problems for an automated liquid
handler. In operation, the handler must be precise enough to place
every probe of a multiple probe array in exact alignment with a
corresponding number of sample containing wells. As well size and
spacing decreases, it becomes more difficult for an automated
handler to reliably place the liquid handling probes directly over
selected sample containing wells.
[0005] The margin for error in locating the plates and wells on the
work bed of the handler and for positioning the probes relative to
the plates and wells decreases as well array density increases. One
aspect of the problem is the precise and consistent location of the
plates and wells upon the work bed. Approaches such as using
manually adjustable clamps or workholders can accurately locate the
sample containing plates upon the work surface, but this type of
system requires a high degree of operator skill and care, a large
number of delicate manual operations and excessive consumption of
time in setting up a bed of plates for treatment in the liquid
handler. In addition this type of system is not well suited for
automated, robotic placement of plates on the bed. It would be
desirable to provide a plate locator that is easy and quick to use,
that does not require great operator skill, that accommodates
robotic placement and that accurately holds and positions sample
containing plates on the work bed of a liquid handler.
SUMMARY OF THE INVENTION
[0006] A principal object of the present invention is to provide an
improved plate locator for positioning and holding sample
containing plates on the work bed of a precision liquid handler.
Other objects are to provide a plate locator that consistently
achieves precise plate positioning; that is easy to use and does
not require great care or skill to locate plates on the work bed;
that is suited to robotic placement of plates on the work bed; and
that is simple and inexpensive yet reliable and rugged.
[0007] In brief, in accordance with the invention there is provided
a plate locator for positioning and holding a four sided plate
having an array of sample containing wells, such as a microplate,
on a work bed of a precision liquid handler having at least one
probe for registration with at least one well of the plate. The
plate locator apparatus includes a flat, planar locator bed adapted
to be secured to the work bed of the precision liquid handler. A
plate receiving nest on the locator bed has four sides
corresponding to the four sides of the four sided plate. The nest
includes rigid stop members extending up from the bed on first and
second sides of the nest and movably mounted holders extending up
from the bed at third and fourth sides of the nest opposite the
rigid stop members at the first and second sides of the nest
Resilient biasing elements are connected between the bed and each
of the movably mounted holders for urging the holders toward the
center of the nest.
BRIEF DESCRIPTION OF THE DRAWING
[0008] The present invention together with the above and other
objects and advantages may best be understood from the following
detailed description of the preferred embodiment of the invention
illustrated in the drawings, wherein:
[0009] FIG. 1 is a simplified, diagrammatic, isometric view of a
precision automated liquid handler with which the plate locator of
the present invention is used;
[0010] FIG. 2 is an enlarged, fragmentary front view of the probe
carrier and multiple probes of the precision liquid handler of FIG.
1, showing the probes in registration with wells of a
microplate;
[0011] FIG. 3 is a top plan view of the work bed of the precision
automated liquid handler of FIG. 1, including an array of plate
nests, each having a plate locator constructed in accordance with
the present invention;
[0012] FIG. 4 is a rear and top perspective view of one of the
plate nests of the work bed of FIG. 3, showing the nest empty and
before a plate is placed into the nest;
[0013] FIG. 5 is a view like FIG. 4 showing the nest with a plate
in place;
[0014] FIG. 6 is a side view taken from the line 6-6 of FIG. 3
showing a plate and portions of a nest with the plate positioned
above the nest;
[0015] FIG. 7 is a view like FIG. 6 showing the plate in place in
the nest;
[0016] FIG. 8 is an enlarged sectional view of a rigid stop member
of the nest, taken along he line 8-8 of FIG. 7;
[0017] FIG. 9 is an enlarged, fragmentary, sectional view taken
along the line 9-9 of FIG. 3, showing the nest and plate in the
positions of FIG. 6 with the plate positioned above the nest;
[0018] FIG. 10 is a view like FIG. 9 showing the plate in place in
the nest;
[0019] FIG. 11 is an exploded sectional view of a movable holder of
the nest; and
[0020] FIG. 12 is an enlarged top plan view of a hoop spring of a
movable holder of the nest.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] Having reference now to the drawings, and initially to FIG.
1, there is shown in simplified, diagrammatic form an example of an
automated precision liquid handler generally designated as 20. The
liquid handler 20 includes a table or work bed 22 below an X-Y-Z
positioning system 24 carrying a probe holder 26. A locator bed 28
is fixed to the surface of the work bed 22. The locator bed
includes a number of nests 30 for holding sample containing plates
32. The probe holder 26 supports individual probes 34 that are
moved by the positioning system 24 to predetermined locations above
the plates 32. As described below, each of the nests 30 includes a
plate locator apparatus generally designated as 36 and constructed
in accordance with the principles of the present invention.
[0022] The X-Y-Z positioning system 24 moves the probe holder 26
above the work bed 22 and positions it with great of precision in
predetermined positions relative to the work bed 22. The system 24
includes an X drive assembly 38 mounted above and to the rear of
the work bed 22 by suitable supports 40. An X drive motor 42, with
an encoder 44, operates a mechanism within an X arm 46 to move a Y
arm 48 from side to side in the X direction. A Y drive motor 50,
with an encoder 52, of a Y drive assembly 54 operates a mechanism
within the Y arm 48 to move a Z arm 56 forward and back in the Y
direction. A Z drive motor 58, with an encoder 60, of a Z drive
assembly 62 operates a mechanism within the Z arm 56 to move the
probe holder 26 up and down in the Z direction. A programmable
controller 63 is connected by cables (not shown) to the motors 42,
50 and 58 and to the encoders 44, 52 and 60. Controller 63 may
include a microprocessor based operating system capable of
controlling the motion of the probe holder 26 in accordance with
programmed instructions saved in memory of the controller and/or
communicated to the controller from a remote source. Linear
encoders may be used in place of the illustrated encoders 44, 52
and 60.
[0023] Each plate locator apparatus 36 positions and holds upon the
work bed 22 a plate 32 including an array of many individual sample
containing wells. The plate 32 has a footprint of about three and
one-half by five inches, and known plates may have an X-Y array of
96 wells in an eight by twelve well pattern, or an array of 384
smaller wells in a sixteen by twenty-four array, or an array of
1,536 nanoliter volume wells in a thirty-two by forty-eight well
pattern. A cross sectional view of a plate 32 of this latter
configuration is seen in FIG. 2, along with the probe holder 26
carrying twelve individual probes 34. This plate 32 includes
thirty-two rows 64 each having forty-eight sample wells 66, one row
64 being seen in FIG. 2. Each well 66 has a width of 1.2
millimeters and the center to center well spacing is 2.25
millimeters. The diameter of each probe 34 is 1.1 millimeters, and
the center to center probe spacing is nine millimeters, or five
wells.
[0024] Each probe 34 can discharge liquid in a droplet size of 0.2
millimeter. The probe holder 26 is moved to the location seen in
FIG. 2 to distribute liquid to the twelve wells 66 that are aligned
under the probes 34. The probe holder 26 is then moved by the X-Y-Z
positioning system 24 to align the probes 34 with another set of
wells 66. In this manner some or all of the wells 66 of the plate
32, and of some or all of the plates 32, can be supplied with
liquid. Because of the small well size and spacing, and the small
probe size and spacing, great precision is required. In order for
the X-Y-Z positioning system to align the probes 34 with wells 66,
the positions of the wells 66 and thus the positions of the plates
32 must be precisely determined. This is the result achieved by the
plate locator 36 of the present invention.
[0025] FIG. 3 shows the locator bed 28, preferably a thick, stable
panel of metal such as aluminum fastened to the work bed of 32 the
liquid handler 20 at three leveling and locating points 68 so that
the location of the locator bed 28 can be precisely adjusted and
fixed on the work bed 22. The locator bed 28 includes a probe rinse
station 70 and probe locator sockets or tubes 72 that can be used
to assess the probe locations for initializing the operation of the
positioning system 24. The locator bed 28 also includes an array of
twelve tray nests 30 in a three by four nest pattern. Each nest 30
includes a plate locator apparatus 36 holding a plate 32. Each
plate 32 may be a 1,536 microtiter plate such as seen in FIG. 2, or
may be of another configuration. Regardless of well size and
configuration, each plate has a four sided base 74 of a consistent,
known size and shape.
[0026] A nest 30 with its plate locator apparatus 36 is seen in
more detail in FIGS. 4 and 5. The plate locator apparatus 36
includes rigid stop members 76 engageable with two sides 74A and
74B of the four sided tray base 74 and movable holders 78 at the
remaining two sides 74C and 74D. When a plate 32 is placed into the
nest 30, the movable holders 78 are contacted by the sides 74C and
74D and are displaced outwardly to permit downward movement of the
base 74 until it rests upon the top surface 80 of the locator bed
28. In this seated position, the sides 74A and 74B are in
engagement with the rigid stop members 76. The rigid stop members
76 are fixed to the locator bed 28 in a known position, and the
rigid stop members 76 determine the position of the plate 32
because they contact two sides of the base 74. As a result, when
the plate 32 is seated in the nest 30, it is in a precisely fixed
and known position and the wells 66 can reliably be accessed by the
positioning system 24 and the probes 34.
[0027] The rigid stop members 76 are stop posts 82. One is shown in
detail in FIG. 8. A threaded opening 84 is made in the top surface
80 at a precisely determined position. The opening 84 has a conical
upper portion 86. The post 82 has a central opening 88 and a
conical base 90 matching the shape of the opening portion 86. Base
90 is seated in the opening portion 86 and this locates the post 82
on the surface 80. A cap screw 92 received in the opening 88 is
threaded into the opening 88 to attach the post 82 in place. The
post 82 is symmetrical about its central axis, with a circular
cross section throughout its length, and can be mounted in any
rotational position.
[0028] The movable holders 78 are biasing posts 92 and are seen in
detail in FIGS. 9-11. For each post 92, a threaded opening 94 is
made in the top surface 80 at a precise location. A stud 96 is
threaded into the opening 96, and the biasing post 92 is placed
over the stud 96 with the stud 96 received in a central opening 98
in the post 92. The stud 96 and the post 92 are symmetrical about
their central axes, with circular cross sections throughout their
lengths, and can be installed in any rotational position.
[0029] Interfacing channels 100 and 102 in the stud 96 and in the
interior of the post 92 define a spring chamber containing a hoop
spring 104. The hoop spring 104 is a wire wound coil spring having
an annular shape similar to that of the spring receiving channel,
with individual windings surrounding the circular spring axis. The
hoop spring 104 resiliently biases the post 92 to a central
position wherein the axes of the stud 96 and post 92 coincide, and
permits the post 92 to be displaced laterally from this central
position while maintain a restoring return force on the post
92.
[0030] FIG. 6 illustrates a plate 32 as it enters the nest 30. The
stop post 82 has an inclined, tapered upper portion 106, and the
post 92 has an inclined, tapered upper portion 108. The surfaces
106 and 108 receive and guide the base 74 of the plate 32 as it
moves downward toward the surface 80. The surface 108 acts as a
cam, and the descending base 74 forces the bias post 92 outwardly
against the force of the hoop spring 104. The stop post 82 has a
cylindrical lower portion 110 immediately adjacent to the surface
80, and the bias post 92 has a cylindrical lower portion 112
immediately adjacent to the surface 80. As the base 74 reaches its
home position against the surface 80, the edges of the base (i.e.
the edges 74B and 74D in FIG. 7) contact these cylindrical surfaces
110 and 112 and there is no tendency for the base to be lifted away
from the surface 80.
[0031] In the initial position of the posts 82 and 92, the spacing
between the cylindrical portions 110 and 112 is slightly less than
the width of length of the base 74 of the plate 32. In the fully
nested, home position of the plate 32, as can be seen from
comparing FIGS. 9 and 10, the hoop spring 104 is compressed at the
region of a radial line extending through the point of contact of
the biasing post 92 with the base 74. The resulting resilient force
applied by the biasing post 92 against the base 74 holds the base
74 firmly against the stop post or posts 82 on the opposite side of
the base 74. Therefore the system of stop posts 82 and biasing
posts 92 guides the descending plate 32 into place and also
precisely determines the nested position of the plate 32.
[0032] Each nest 30 includes three stop posts 82 and two biasing
posts 92 (FIGS. 3-5). Two stop posts 82 are located near opposite
ends of one of the longer sides 74B of the base 74. A third stop
post is located at an adjacent side 74A near the corner with side
74B. These three posts define an unambiguous, certain position for
a plate 32 held in the nest. No rotation or deviation of the plate
32 from the intended position can occur when the base 74 contacts
the three stop posts 82. The two biasing posts 92 are located on
the two sides 74C and 74D opposite the sides 74A and 74D engaged by
the stop posts 82. These two biasing posts 92 apply forces in two
perpendicular directions to force the base 74 firmly against the
three stop posts 82. This provides a simple arrangement that is
inexpensive to fabricate and assemble.
[0033] No special skill or care is needed to place a plate 32 into
the nest where is it held in a precise, known position. In
addition, the plate can be removed with a simple lifting motion
because the plate is not latched or locked in place by any
structure engaging a top surface of the plate. The plate locator
apparatus 36 of the present invention is well suited for robotic
plate placement and removal because the final positioning of the
plate is carried out by the plate locator 36 associated with the
locator bed 28 and not by the person or machine that places the
tray onto the surface 80. To facilitate robotic placement and
removal, each nest 30 includes opposed recesses 114 in the surface
80 at opposite sides of the nest. The recesses 114 provide
clearance for gripping the edges of the base 74.
[0034] While the present invention has been described with
reference to the details of the embodiment of the invention shown
in the drawing, these details are not intended to limit the scope
of the invention as claimed in the appended claims.
* * * * *