Test tube rack assembly

A test tube rack assembly including a test tube rack pivotally connected to a base having end support structure for allowing pivoting motion of the test tube rack with respect to a stationary base about a horizontal axis. A selectively actuable connector is affixed to at least one of the base end supports and includes a stud selectively engageable with one of a plurality stud receivers associated with the test tube rack for pivoting movement therewith. Each of the stud receivers defines a different angular position of the test tube rack with respect to the base. Preferably, a holder is disposed between the base and the test tube rack. A pair of holder end supports, comprising spring plates, have locking and alignment structure which mates with structure on the ends of the test tube rack to allow releasable, secure engagement between the holder and the rack.

BACKGROUND OF THE INVENTION 
The present invention generally relates to test tube holding apparatus and, 
more specifically, to a test tube rack assembly suitable for mounting a 
plurality test tubes during scientific procedures. 
During scientific experimentation, such as biological testing procedures, 
it is often necessary to utilize a number of test tubes holding liquid 
culture specimens. The test tubes are generally held in racks while the 
culture specimens are grown. These racks may also be attached to shaking 
or stirring devices, such as orbital shaker tables, to mix the contents of 
the test tubes and enhance the culture growth activity. The test tubes may 
also be incubated, refrigerated and subjected to different lighting 
conditions during such experiments or culturing procedures. 
As cultures are grown in test tubes, it is generally advantageous to 
maximize direct contact of the culture medium with air. Shaking the test 
tubes is one way to increase the exposure of culture medium to air at the 
top of the test tube. In this regard, shaking the culture medium creates a 
larger undulating surface area in the medium. Shaking also ensures that a 
greater volume of culture medium is brought to the surface to directly 
react with air at the top of the test tube. 
Another manner of increasing the surface contact area of the culture medium 
with air for reaction purposes is to angle the test tubes from vertical 
such that the upper surface of the medium takes on a larger, oval shape. 
Various make-shift ways of accomplishing this have been used by scientists 
and other laboratory personnel. These have included leaning individual 
test tubes or the rack in which they are held against other structure at 
an angle and using tape to secure the test tubes against the structure as 
they are being stirred or shaken. 
Certain test tube racks or holders have been proposed for orienting test 
tubes at an angle to increase the rate of culture growth by increasing 
surface area exposure of the culture. In this regard, U.S. Pat. No. 
4,932,533 discloses a test tube transportation container having an insert 
for holding the test tubes and culture medium contained therein at a 
predetermined, fixed angle. This holder does not allow adjustment of the 
angle and, as it is designed for transportation or shipping purposes, the 
holder is not particularly well suited for laboratory use. 
An adjustable test tube carrier is disclosed in U.S. Pat. No. 4,770,381. In 
this patent, one embodiment of the carrier is angularly adjustable by way 
of a curved slot which carries a threaded stud secured by a wing nut. The 
adjustment feature and other aspects of this holder suffer from certain 
disadvantages. For example, while the test tube carrier has two extreme 
angular positions defined at the ends of the curved slot, it does not 
provide the ability to repeatedly set the carrier at a plurality of 
discrete angular positions between these extremes. The lack of assurance 
that test tubes in different experiments or tests are being held at the 
same angle could lead to misleading results in some cases. Also, it may be 
awkward for one operator to angle the test tube carrier and then tighten 
down the wing nut while holding the test tube carrier at the desired 
angle. With a wing nut and threaded stud securing arrangement, there is 
also the possibility that the test tube carrier will loosen with respect 
to the stationary base during a shaking procedure. 
Finally, the prior art suffers from still further disadvantages with 
respect to the ability of the test tube rack to be quickly and rigidly 
secured to a shaking apparatus. In order to obtain the rigid connection 
between the shaking apparatus and the test tube rack in the past, tedious 
fastening methods have been used which do not allow the entire rack full 
of test tubes to be quickly removed from a shaking apparatus, refilled 
with test tubes and replaced or alternatively replaced by another rack 
filled with test tubes. Therefore, setting up tests and experiments and 
changing over from one test tube rack to another has generally been a time 
consuming process. 
It would therefore be desirable to provide a test tube rack assembly which 
allows versatile adjustment of the angle of the test tube rack and which 
includes other features which allow rigid attachment of the entire 
assembly to a shaking apparatus yet allow quick attachment and release of 
the test tube rack with respect to other support portions of the assembly. 
SUMMARY OF THE INVENTION 
It has therefore been one object of the present invention to enable 
orientation of a test tube rack at a plurality of discrete, repeatable 
angular positions separated by relatively small angular increments. 
It has been another object of the invention to allow quick, rigid and 
releasable connection of a test tube rack to a mounting support or base 
structure. 
It has been a further object of the invention to provide a test tube rack 
assembly which is easily used in conjunction with chest-like enclosures, 
such as incubators or refrigeration devices, having an upper opening 
through which the test tube rack is vertically inserted and removed. 
To these ends, the test tube rack assembly of the present invention in one 
general aspect includes a base comprising a bottom support and a pair of 
upright end supports. A test tube rack is pivotally connected between the 
base end supports. The test tube rack also includes a pair of end supports 
with test tube supporting structure extending therebetween. A pivot 
connection is provided between the base end supports and the test tube 
rack end supports with the pivot connection allowing a pivoting motion of 
the test tube rack with respect to the base about a horizontal axis. A 
selectively actuable connector is affixed to at least one of the base end 
supports and includes a stud selectively engageable with one of a 
plurality stud receivers associated with the test tube rack for pivoting 
movement therewith. Each of the stud receivers defines a different angular 
position of the test tube rack with respect to the base. 
In the preferred embodiment, the test tube rack assembly includes a test 
tube rack holder disposed between the test tube rack and the base. The 
test tube rack holder includes a pair of end supports which are each 
pivotally connected to a respective base end support by a pivot pin or 
rivet centrally disposed between front and rear edges of the base. The 
stud receivers preferably comprise arcuately spaced holes in the end 
supports of the holder and the selectively actuable connector is a 
spring-loaded plunger mechanism for moving the stud axially between 
engaged and disengaged positions with respect to the holes. The plunger is 
spring-biased to normally hold the stud in an engaged position and 
includes a hold-open feature allowing the stud to be temporarily held in a 
disengaged position as an angular adjustment is made to the holder and the 
rack. 
The holder end supports and rack end supports have mating locking structure 
for allowing releasable, secure engagement between the holder and the 
rack. The holder end supports more specifically comprise upright spring 
plates which are normally disposed in a locking structure engagement 
position. The spring plates are capable of being spread or biased 
outwardly to both receive the test tube rack and disengage the locking 
structure during removal of the test tube rack. 
In part, the locking structure of each spring plate is formed by inwardly 
extending portions of the spring plates which engage upwardly facing 
surfaces of the test tube rack end supports to prevent upward movement of 
the rack within the holder. In the preferred embodiment, these inwardly 
extending portions comprise inward bends in the spring plates. The spring 
plates are formed integrally with a bottom plate of the holder from a 
single sheet of resilient material, such as stainless steel. The spring 
plates are bent upwardly from the bottom plate and further bent to include 
the inward, locking bends mentioned above as well as upper, outward bends 
which act as cam surfaces. These cam surfaces allow the spring plates to 
be spread apart during insertion of the test tube rack. 
The end supports of the test tube rack and holder also include mating 
alignment and locking structure for both aligning the test tube rack as it 
is inserted within the holder and preventing movement in forward rearward 
and downward directions with respect to the holder and base. The alignment 
and locking structure generally includes mating male and female portions 
of the rack and holder which allow insertion and removal of the rack in 
upward and downward directions. More specifically, respective recesses or 
cutouts are formed in the test tube rack end supports and these slidingly 
receive alignment members extending inwardly from the spring plates. 
Further advantages and objects of the invention will become more readily 
apparent from the following detailed description of a preferred embodiment 
of the invention taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Generally referring to FIGS. 1-3, the present invention is preferably 
embodied in a test tube rack assembly 10 including three major components. 
These components include a test tube rack 12, a test tube rack holder 14 
and a base 16. As will be discussed in detail below, rack 12 and holder 14 
pivot as a unit with respect to base 16 and may be locked at one of 
several discrete angles, such as the angle shown in FIG. 3. As will also 
be discussed below, holder 14 and test tube rack 12 are further designed 
to be connected together in a quickly releasable, yet stable manner. 
Specifically, and as best shown in FIGS. 1 and 2, test tube rack 12 
includes a pair of vertical end supports 18, 20 and test tube supporting 
structure 22 rigidly affixed therebetween. Test tube supporting structure 
22 preferably comprises horizontally oriented, vertically spaced plates 
24, 26, 28. The two upper plates 24, 26 have respective, aligned holes 30, 
32. Test tubes 34 (FIG. 2) may be inserted through and laterally supported 
by respective vertically aligned holes 30, 32. As further shown in FIG. 2, 
test tubes 34 rest on upper surface 36 of bottom panel 28. End supports 
18, 20 include handles 38, 40 for allowing rack 12 to be carried by the 
user and inserted and removed from holder 14. 
Rack 12 also includes alignment and locking structure for engagement with 
mating structure of holder 14. With respect to rack 12, this structure 
includes alignment and locking recesses or cut-outs 41, 43 which provide 
for alignment and guidance as rack 12 is inserted and removed from holder 
14 and, as discussed below, prevent forward, rearward and downward 
movement of rack 12 after it has been fully inserted into holder 14. 
Further locking structure is provided on rack 12 for preventing upward 
movement of rack 12 once it has been fully inserted into holder 14. This 
structure comprises upper surface portions 50, 52 of rack end support 18 
and upper surface portions 54, 56 of rack end support 20 all of which are 
engaged by mating locking structure of holder 14 as described below. 
As best illustrated in FIG. 1, test tube rack holder 14 includes a pair of 
end supports 60, 62 which preferably comprise spring locking members or 
plates. End supports or spring plates 60, 62 are formed integrally with a 
bottom support plate 64 from a sheet of resilient material. This material 
is preferably T-301 stainless steel which is 0.20 inches in thickness, 
however, it is contemplated that polymer or plastic materials or other 
metals may be used as well. 
Still referring to FIG. 1, holder 14 includes male alignment structure, as 
mentioned above, which preferably comprises alignment members 66, 68 
formed from the same plate material as spring plates 60, 62. Alignment 
members 66, 68 are permanently affixed to respective inside surfaces 
thereof by spot welds 70, 72 and clinching rivets 74, 76. Each alignment 
member 66, 68 includes respective inward bend portions 78, 80 and 82, 84 
which essentially form rails to ride against the front and rear cut-out 
surfaces 42, 44 of recess or cut-out 41, 43. The lower end of each recess 
or cut-out 41, 43 further includes diverging or outwardly angled surfaces 
46, 48. Surfaces 46, 48 effectively widen the lower portions of the 
respective recesses or cut-outs 41, 43 to allow easier location of the 
male alignment members or rails 66, 68 into recesses or cut-outs 41, 43. 
When rack 12 is fully inserted in a downward direction into holder 14, the 
upper ends of rails 78, 80 and 82, 84 stop further downward movement 
thereof by engaging upper surfaces 45, 47 of recesses or cut-outs 41, 43. 
Forward and rearward movement of rack 12 is prevented by engagement of 
rails 78, 80 and 82, 84 with front and rear surfaces 42, 44 of recesses or 
cut-outs 41, 43. 
Referring now to FIGS. 1-3, holder end supports or spring plates 60, 62 
include handle cut-outs 86, 88 which receive handles 38, 40 of rack 12 as 
shown in FIGS. 2 and 3. Each spring plate 60, 62 includes further locking 
structure comprising inward bend portions 90, 92 and 94, 96 on either side 
of handle cut-outs 86, 88 for respectively engaging upper surfaces 50, 52 
and 54, 56 of rack 12. As will be appreciated from FIGS. 2 and 3, once 
rack 12 is fully inserted into holder 14, upward movement of rack 12 is 
prevented by engagement of lower surfaces 90a, 92a and 94a, 96a of bend 
portions 90, 92 and 94, 96 with upper surfaces 50, 52 and 54, 56 of rack 
end supports 18, 20. 
To facilitate the insertion of rack 12 into holder 14, the upper ends 98, 
100 of holder end supports or spring plates 60, 62 are bent outwardly from 
bend portions 90, 92 and 94, 96. As will be appreciated best from FIG. 2, 
during the downward insertion of rack 12 into holder 14, the bottoms of 
rack end supports 18, 20 will slide down the upper cam surfaces 98a, 100a 
and spread the upper portions of spring plates 60, 62 outwardly as shown 
in phantom lines. Once upper surfaces 50, 52 and 54, 56 of rack end 
supports 18, 20 pass the lower edges 98b, 100b of upper ends 98, 100, 
upper ends 98, 100 snap back into their normal upright position as shown 
in solid lines in FIG. 2. As will be discussed in detail below, each 
holder end support or spring plate 60, 62 further includes a plurality of 
arcuately spaced holes, including center holes 102a, 104a, which define a 
vertical orientation of rack 12 and holder 14 as well as additional 
arcuately spaced holes 102, 104 which allow discrete, repeatable angular 
adjustments to be made in the orientation of rack 12 and holder 14. Holes 
102 and 104 are successively placed on both sides of the respective center 
holes 102a, 104a so as to define 15.degree. angular increments in the 
adjustment of rack 12 and holder 14. Preferably, a total of 45.degree. of 
adjustment is provided for in both directions relative to vertical. 0f 
course, the increments and total adjustment capabilities may be modified 
according to the needs of the application. 
Referring again to FIG. 1, base 16 of assembly 10 comprises end supports 
110, 112, a bottom panel 114 having mounting holes 116, as well as front 
and rear sides 118, 120. Holes 116 are used to accommodate fastening 
screws for holding base 16 to another structure, such as a shaking 
apparatus (not shown). As in the case of holder 14, base 16 is preferably 
formed from a single sheet of stainless steel by bending end supports 110, 
112 and front and rear sides 118, 120 upwardly from bottom mounting plate 
114. To provide for a more rigid structure, front and rear sides 118, 120 
may be rigidly connected to end supports 110, 112, such as by welding at 
their junctions. 
Pivot pins 122, 124 are provided to form a pivot connection between holder 
end supports or spring plates 60, 62 and base end supports 110, 112 in 
opposite directions about a horizontal axis 121. Pivot pins 122, 124 and 
axis 121 are disposed centrally between front and rear sides 118, 120 of 
base 112. Pivot pins 122, 124 preferably comprise shoulder rivets which 
extend through respective holes 123, 125 in base end supports 110, 112. As 
will further be appreciated best from FIG. 1, shoulder rivets 122, 124 
further extend through the respective clinching rivets 74, 76 in spring 
plates 60, 62. Shoulder rivets 122, 124 are fastened conventionally 
between base end supports 110, 112 and spring plates 60, 62 such that 
holder 14 is pivotally supported on base 16. 
Referring to FIGS. 1 and 2, each base end support 110, 112 further includes 
a selectively actuable connector 126, 128 which functions with holes 102a, 
104a to lock rack 12 and holder 14 in a vertical orientation or with holes 
102, 104 to lock rack 12 and holder 14 at any one of several discrete 
angular positions. Specifically, each connector comprises an identical 
spring-loaded plunger mechanism and therefore like reference numerals of 
each refer to identical structure in the drawings. The spring-loaded 
plungers of the preferred embodiment are manufactured by Southco, Inc. 
under part no. 56-10-301-20. Each spring-loaded plunger 126, 128 is 
mounted to a portion 130 of each base end support 110, 112 which has been 
punched or deformed outwardly approximately 0.120 inches for reasons to be 
discussed below. 
Spring-loaded plungers 126, 128 include a cylindrical portion 132 which is 
rigidly fastened to the corresponding mounting portion 130 by a threaded 
sleeve 131, as shown in the left hand side of FIG. 1. As such, it will be 
appreciated that outwardly deformed mounting portions 30 prevent 
interference between sleeve 131 and the outer surfaces of spring plates 
60, 62 during pivoting motion about axis 121. A stud 136, shown extending 
through sleeve 131 in the left hand side of FIG. 1, is movable with each 
handle 134 inwardly and outwardly with respect to sleeve 131 and with 
respect to holes 102, 104. Each handle 134 and attached stud 136 is spring 
biased in an inward or normally engaged position with respect to holes 
102, 104 or 102a, 104a. The spring-loaded plungers 126, 128 of the 
preferred embodiment include a hold-open feature which allows stud 136 to 
be pulled outwardly and held in a disengaged position against the spring 
force by twisting handle 134 after pulling it out. This allows an operator 
to make the appropriate angular adjustment of rack 12 and holder 14 
without manually holding each plunger 126, 128 with its stud 136 in a 
disengaged position during the adjustment. 
Angular orientation of test tubes 34 is often important to procedures 
involving the growth of cultures. It will be appreciated from FIGS. 4 and 
4A that a vertically oriented test tube 34 holding a liquid culture medium 
140 causes the medium to have circular surface area 142 (FIG. 4A). On the 
other hand, angling test tube 34 as shown in FIG. 5 causes culture medium 
140 to have a larger oval shaped surface area 144. Surface area 144 
exposes more of culture medium 140 to the air above culture medium 140. 
This results in faster culture growth. The present invention provides for 
a range of angles at which a plurality of test tubes 34 may be oriented 
and further provides for precise repeatability of such orientations. This 
repeatability is often important when conducting multiple tests or 
procedures which require the same control parameters for each procedure. 
OPERATION 
Referring first to FIG. 3, with holder 14 angled in the position shown, the 
front portion of base 16 may be rigidly secured to another structure, such 
as a shaking or stirring apparatus by inserting suitable fasteners (not 
shown), such as screws, through holes 116 as necessary. Rack 12 may 
optionally be inserted with holder 14 during the securement of base 16, 
however, it is easier to secure base 16 with rack 12 detached from holder 
14. Holder 14 may then be adjusted to an oppositely angled orientation to 
that shown in FIG. 3 after pulling plungers 126, 128 outwardly into their 
hold-open positions to disengage studs 136 from holes 102, 104 (FIG. 1). 
The rear portion of base 16 may then be rigidly secured using additional 
fasteners inserted through an appropriate number of mounting holes 116 
along a rear portion of base 16. 
Referring now to FIGS. 1 and 2, with holder 14 preferably returned to a 
vertical orientation, rack 12 is snapped securely into place within holder 
14 by simply sliding rack 12 downwardly into holder 14. The easy, 
vertically downward insertion of rack 14 into holder 14 is especially 
advantageous when base 16 and holder 14 are mounted within an enclosure, 
such as an incubator or refrigeration device, having a top opening. During 
the downward sliding motion of rack 12, spring plates 60, 62 will be 
spread outwardly as shown in dotted lines in FIG. 2 and then surfaces 42, 
44 of alignment recesses or cut-outs 41, 43 will engage alignment members 
78, 80 and 82, 84 in a sliding manner. Rack 12 may be pushed downwardly 
until upper surfaces 50, 52 and 54, 56 of rack end supports 18, 20 pass 
bends 98b, 100b in the respective spring plates 60, 62 and, 
simultaneously, upper ends of alignment members 78, 80 and 82, 84 abut 
against upper surfaces 45, 47 of recesses or cut-outs 41, 43. At this 
point, spring plates 60, 62 will return to their original upright or 
vertical position and bend portions 90, 92 and 94, 96, in conjunction with 
plates 66, 68 and recesses or cut-outs 41, 43, will lock rack 12 against 
any substantial movement with respect to holder 14. 
Referring generally to FIGS. 1-3, to make the desired angular adjustment of 
test tubes 34, such as to the angle shown in FIG. 3, handles 134 on each 
side of base 16 are pulled outwardly and twisted into their hold-open 
positions to disengage studs 136 from holes 102a, 104a. Rack 12 and holder 
14 may then be pivoted about axis 121 to the desired angle and both studs 
136 of spring-loaded plungers 126, 128 may be re-engaged with holes 102, 
104 corresponding to that angle. This is accomplished by twisting handles 
134 in the opposite direction and allowing the spring force of each 
plunger 126, 128 to bias studs 136 inwardly into respective holes 102, 
104. 
To remove rack 12 from holder 14, assembly 10 is preferably returned to its 
vertical orientation as shown in FIG. 2 by disengaging and re-engaging 
plungers 126, 128 in center holes 102a, 104a (FIG. 1). Upper portions 98, 
100 are then biased outwardly to disengage bends 90, 92 and 94, 96 and 
allow rack 12 to be lifted vertically out of holder 14. 
Although the foregoing description details one preferred embodiment of the 
invention, Applicants' intention is not to be bound by such details. 
Rather, several inventive concepts and features have been disclosed by way 
of this detailed embodiment. Many modifications and substitutions for the 
details presented herein may be made without departing from the spirit and 
scope of the invention as covered by the appended claims.