U.S. patent number 3,674,198 [Application Number 05/048,142] was granted by the patent office on 1972-07-04 for receptacle holder for centrifuges.
Invention is credited to Gunter Eberle.
United States Patent |
3,674,198 |
Eberle |
July 4, 1972 |
RECEPTACLE HOLDER FOR CENTRIFUGES
Abstract
A holder for centrifuges, for receiving specimen containers such
as test tubes holding substances to be centrifuged, comprising
three major parts which are connected in a form-fitting manner,
namely a stirrup member, a cup member therein, and a frame in the
latter, with bores in the frame for the test tubes. The cup member
is preferably transparent, and the frame has apertured side
portions that allow inspection of the substances in the test tubes.
Photo-electric means may be provided for automatically controlling
the energization of the centrifuge, depending on the progress of
the settling process.
Inventors: |
Eberle; Gunter (D-7200
Tuttlingen, DT) |
Family
ID: |
27510042 |
Appl.
No.: |
05/048,142 |
Filed: |
June 22, 1970 |
Current U.S.
Class: |
494/7; 211/74;
494/20; 494/10 |
Current CPC
Class: |
B04B
5/0414 (20130101); B04B 5/0421 (20130101); B04B
5/04 (20130101); G01N 21/07 (20130101); B04B
13/00 (20130101); B04B 2005/0485 (20130101) |
Current International
Class: |
B04B
5/00 (20060101); B04B 5/04 (20060101); B04B
13/00 (20060101); G01N 21/03 (20060101); G01N
21/07 (20060101); B04b 009/12 () |
Field of
Search: |
;233/26,27,1R ;88/14
;211/74 ;248/311 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Franklin; Jordan
Assistant Examiner: Krizmanich; George H.
Claims
What I claim is:
1. A holder for centrifuges, adapted to receive a plurality of
specimen containers such as test tubes holding substances to be
centrifuged; the holder comprising, in combination: a substantially
U-shaped stirrup member having a bottom plate and rigid therewith
two upstanding shanks, the latter with journal pins in their
terminal portions, for pivotal insertion in the head of the
centrifuge; at least one cup member inserted in a form-fitting
manner in said stirrup member between said shanks and held in
position on said bottom plate; and at least one frame member
inserted in a central opening of said at least one cup member, and
having therein a plurality of bores adapted to receive test tubes,
wherein said at least one cup member is made of a substantially
transparent material, and said at least one frame member includes a
substantially square-shaped hollow body portion, with apertured
side portions that allow inspection of substances within test tubes
to be inserted in said frame, a head portion having said bores
therein to receive test tubes, and a bottom adapted to support
terminal portions of test tubes when inserted therein.
2. The receptacle holder as defined in claim 1, further comprising
fastening means on respective portions of said journal pins and
said shanks, adapted to take up substantially high centrifugal
forces.
3. The receptacle holder as defined in claim 1, wherein said
stirrup member and said bottom plate are made from a single piece
of material.
4. The receptacle holder as defined in claim 1, further comprising
connecting means between said stirrup member and said bottom plate
to immobilize the same in a form-fitting manner with respect to
said stirrup member.
5. The receptacle holder as defined in claim 1, further comprising
locating means in mating portions of said stirrup member and said
at least one cup member to immobilize the same in a form-fitting
manner with respect to said stirrup member.
6. The receptacle holder as defined in claim 4, wherein said shanks
are elongated, flat members and said locating means is constituted
by elongated indentations in two opposite side walls of said at
least one cup member, with a shape allowing nesting therein of at
least terminal portions of said shanks.
7. The receptacle holder as defined in claim 1, including a housing
and a rotatable centrifuge head therein, said holder being secured
to said head and describing A continuous flight path within the
housing when said head is rotated, and said at least one cup member
is of a substantially transparent material, and further comprising
a stroboscope lamp and at least one photo-electric means secured to
said housing, said flight path being between said lamp and said
photo-electric means, and circuit means connected to said at least
one photo-electric means to provide a signal for controlling the
energization of the centrifuge.
8. The receptacle holder as defined in claim 7, wherein said at
least one photo-electric means includes at least two separate
photocells aligned with the apertured side portions so that test
tubes as they pass in the flight path provide separate output
signals for said circuit means, responsive to the light - dark jump
and the dark - light jump in transparency during the settling of
the substances therein.
9. The receptacle holder as defined in claim 1, wherein said
stirrup member includes immobilizing means for holding in place
said at least one cup member.
10. The receptacle holder as defined in claim 9, wherein said
immobilizing means is in the form of a girdle member attached to
said shanks, adapted to hold at least two of said cup members.
11. The receptacle holder as defined in claim 9, wherein said
immobilizing means is in the form of at least a pair ledge members
attached to said bottom plate.
12. The receptacle holder as defined in claim 9, wherein said
immobilizing means is in the form of a trough attached to said
bottom plate, adapted to hold a plurality of said cup members.
Description
The invention relates to a receptacle holder for centrifuges, for
receiving specimen containers such as test tubes and the like, to
be pivotally supported in the centrifuge head by means of lateral
journal pins and corresponding grooves in the centrifuge head.
Hitherto known receptacle holders, provided for receiving several
specimen containers, such as test tubes, were usually machined from
a preferably light-metal block from the solid, and they were
provided either with individual blind-hole bores with the diameter
of a test tube or with a substantially rectangular recess to
receive a supporting frame.
Receptacle holders provided with individual blind bores, each to
receive a test tube, had not only the disadvantage to be rather
expensive on account of the machining from the solid with a view to
obtaining the required sturdiness but they also had a substantial
mass which involved exceedingly high centrifugal forces during the
operation.
A further disadvantage constituted in that rubber stoppers had to
be inserted into the individual blind-hole bores for protecting the
test tubes yet the latter broke quite frequently during the
centrifuging process whereafter it was rather tedious and
time-consuming to clean the respective blind bore or bores.
Even receptacle holders which were provided with a substantially
rectangular recess or cut-out for simultaneously receiving several
specimen containers placed in a support frame had to be machined
from the solid and were consequently similarly expensive and heavy.
They necessarily involved very considerable centrifugal forces that
acted primarily on the supporting journal pins. On account of these
high forces prevailing in both types of known devices it was not
even possible separately to manufacture the journal pins and insert
them subsequently into the receptacle holders because neither screw
connections nor rivets were capable of withstanding the enormous
centrifugal forces. The result was that even the journal pins or
trunnions had to be machined from the solid material.
Another, considerable drawback of known receptacle holders consists
in that these devices, being closed on their sides and made from a
non-transparent material, such as mostly steel, do not allow
inspection of the lower portions of the specimen containers, such
as from the sides. Thus one has to set the centrifuging time
according to empirical results or intermediate tests have to be
made for which the centrifuge has to be stopped in each instance in
order to remove and inspect the individual specimen containers.
This procedure naturally considerably disturbs and handicaps the
operation.
It is an object of the present invention to provide a receptacle
holder which eliminates the aforesaid disadvantages, is cheaper to
manufacture, lighter in weight, does not develop exceedingly high
centrifugal forces, and is simple to manipulate.
It is also one of the objects of the invention to allow the
inventive receptacle holder simultaneously to receive a plurality
of specimen containers, such as test tubes, in the form of a
battery or set, to be individually withdrawable from the
holder.
Further, a receptacle support frame should be provided which allows
overall inspection of the lower portions of the test tubes, thereby
allowing the lab operator to recognize the results of the
centrifuging operation at a glance, without having separately to
remove one or more of the individual specimen containers.
It is also one of the objects of the inventive receptacle holder to
provide the facility of carrying out a continuous observation of
the material being centrifuged, during the entire process, so that
the duration of centrifuging is not dependent any more on estimated
or empirical values but it can made directly dependent upon the
centrifuging effect itself, that is, upon the attained
sedimentation in the specimen receptacles.
The inventive receptacle holder is characterized, in one of its
important aspects, by a substantially U-shaped stirrup with a
bottom plate and journal pins at the ends of its shanks, at least
one cup that can be inserted in a form-fitting manner into the
stirrup, as well as at least one receptacle supporting frame to be
inserted in the cup or cups, with lateral walls open in their lower
regions.
As compared to hitherto known devices, the inventive receptacle
holder has the following important advantages:
The stirrup is swingably supported in the head of the centrifuge
and, while it has to withstand all the centrifugal inertial forces,
is much simpler and cheaper to make and also much lighter in weight
so that, as a result, the centrifugal forces to be endured by the
pins are considerably lower, allowing substantially higher
centrifuging speeds as well as a simpler construction of the
centrifuge head itself.
The cup, insertable in a form-fitting manner into the stirrup, is
similarly simple and cheap to manufacture and has a very low weight
whereby it does not substantially contribute to an increase in the
centrifuging forces. It is actually the purpose of this cup to
receive, in the case of a breakage of a specimen container, both
its contents as well as the broken pieces, such as glass fragments
of a test tube, and to insure that neither the liquid or other
substance nor the broken parts of the specimen container are
whirled into the centrifuge drum.
In this manner the contamination of the centrifuge drum in case of
a breakage of a specimen container and the development of an
unbalance are both eliminated. It is known that for each
centrifuging process simultaneously several receptacle holders are
suspended in the centrifuge heads, in a manner symmetrical to the
center axis, so as to insure a centrifuging process which is
possibly free from unbalance.
The receptacle support frame inserted in the cup and receiving a
battery of individual specimen containers has the advantage that
simultaneously, by a single movement, several specimen containers
can be handled whereby a mix-up between individual containers is
eliminated or at least considerably reduced. These support frames
are furthermore very useful as stands for a number of specimen
containers, and after the centrifuging they can be placed on a
suitable surface (table, counter top, etc.).
The open arrangement of the side walls of the receptacle support
frame, at least in its lower portion, allows inspection by the
operator of all inserted specimen containers and their contents so
that it is not necessary to remove the individual specimen
containers from the support frame in order to make a visual
inspection.
This receptacle support frame is similarly simple and cheap to
produce. Only its bottom on which the specimen containers rest is
exposed to the centrifugal forces of the containers and their
contents, thus the receptacle frame does not require a particularly
high rigidity so that it can consequently be made, for example,
from a light plastic material or any other suitable light-weight
material, in a simple and light constructional arrangement.
The inventive receptacle holder consequently exhibits not only the
advantages of being simple to produce, cheaper and lighter, as
compared to the hitherto known devices serving the same purpose,
but it has the added advantage that the manipulation of the
specimen containers is considerably simplified. This means that at
the same time a substantial saving is obtained in operating time
and effort.
As a further, optional feature of the inventive device, the stirrup
and the bottom plate can be made from a single piece. This
expedient results in a further reduction in costs and
simplification of the manufacture.
According to the size of the stirrup it might be advisable,
according to the invention, to make the stirrup and the bottom
plate separate, these elements being subsequently connected by
screws or other conventional expedients in a form-fitting
manner.
Unlike the known receptacle holders in which the journal pins were
made from the same material and machined from the solid, the
invention also provides separate pins which can be riveted or
screwed into the shanks of the stirrup. This also results in a very
considerably further reduction in costs and simplification of the
manufacturing process.
Another preferred, optional feature of the invention resides in
that the stirrup can be made from a plastic material or a light
metal.
It is suggested to provide the stirrup with an upper girdle or
frame member and/or upwardly directed safety members disposed on
the surface of its bottom plate, such as ledges, pins, notches and
the like, for supporting the cup or cups.
Thus the latter are held in place in a simple manner, and it is not
necessary to provide the walls or other parts of the cups with some
supporting profiles with which to be attached to or secured with
respect to the stirrup.
It is advisable and suggested by the invention to provide the
bottom plate with a trough for receiving the lower portion of the
cup or cups.
In accordance with another recommended feature of the invention,
the stirrup, made in different sizes, is designed to receive
several cups and/or support frames.
It is thus possible to lodge several receptacle supporting frames
within the stirrup, thereby multiplying the capacity of the device,
while using a standardized size of support frames and possibly also
of matching cups.
It is also possible to make the stirrup and the cup, or either of
them, in various sizes, to receive different quantities of
receptacle supporting frames.
In this embodiment only a single cup is required, the size of which
corresponds to that of the stirrup, and in which several smaller
receptacle support frames of standard size can be inserted. A
further reduction in costs and weight is achieved, in combination
with an increase in specimen-container receptivity.
The cup itself is preferably made with thin walls, from a plastic
material insensitive to acids, lyes and other aggressive chemical
substances. This avoids the cups to be damaged, such as, for
example, when a specimen receptacle should break and its content
spilled into the cup.
The invention suggests a very simple construction for the cups
insofar as two opposite lateral walls may have indentations or
depressions for receiving the stirrup shanks.
Another rather important feature consists in that the cups are made
of a transparent, preferably glass-clear plastic, such as
plexiglass.
This allows not only the contents of the individual specimen
containers to be observed from the outside through the cup walls
and the lateral openings of the receptacle support frame but the
possibility is also give continuously to observe during the
centrifuging process any changes occurring in the condition of the
material being centrifuged, and to photo-electrically to sense and
use the changing transparency of the material. During sedimentation
in the course of the centrifuging action a dense, opaque deposit
develops, as a rule, in the lower portion of the specimen
containers, while the upper portion clarifies and becomes
transparent.
The receptacle supporting frame consists preferably of a
substantially square-shaped hollow body with apertured side walls,
a bottom and a massive top portion, the latter having perpendicular
through bores, preferably arranged in rows, each for receiving a
specimen container or test tube.
According to yet another feature of the invention one or more
photo-electric sensors or transducers can be disposed above the
flight path of the receptacle holder, assumed during centrifuging,
while one or more stroboscope lamps and the like can be arranged
below the flight path, their pulse or light frequency being adapted
to or varied in accordance with the rotational speed of the
centrifuge.
It is of course possible to observe the material contained in the
individual receptacle holders and being centrifuged by means of one
or more stroboscope lamps through the transparent cups, the
inventive device furthermore allowing the centrifuge to be
automatically stopped or disconnected when the required effect has
been achieved. The man skilled in the art can of course reverse the
above-mentioned arrangement of the photo transducers and
stroboscope lamps; it is however advisable to keep the former
possibly close to the flight path of the receptacle holder.
With a view to attaining a relatively high triggering sensitivity
of this supervisory or control arrangement, the invention
furthermore suggests two groups of photo-electric cells to be used
of which one is responsive to the light dark jump and the other,
conversely, to the dark - light jump, a known electronic circuit,
for example a logic circuit, being provided for producing a control
signal or performing an operational function (stopping of the
centrifuge).
Other objects and many of the attendant advantages of the invention
will be readily appreciated as the same becomes better understood
by reference to the following detailed description, when considered
with the accompanying drawings, wherein
FIG. 1 is a disassembled (exploded) perspective view showing an
exemplary embodiment of the inventive receptacle holder for
centrifuges, with its three major parts: a stirrup, a cup and a
frame;
FIG. 2 is a vertical section, partly broken away, along line 2 -- 2
in the central section of FIG. 1;
FIG. 3 is a modified stirrup as compared to the lower section of
FIG. 1;
FIG. 4 is a vertical, partly sectional view taken along line 4 -- 4
of FIG. 3;
FIG. 5 is a horizontal, partly sectional view taken along line 5 --
5 of FIG. 3;
FIG. 6 is a perspective view of the three major parts of FIG. 1
completely assembled and ready for use;
FIG. 7 is a somewhat oblique top view of a centrifuge head, on a
reduced scale, adapted to be used with the inventive receptacle
holder;
FIG. 8 is a top view of a multiple assembly having several frames
and cups therein;
FIG. 9 is a top view similar to that of FIG. 8 of an assembly
including a single frame with four cups therein, the bottom plate,
shanks and journal pins having been omitted;
FIG. 10 is a perspective view of another modified stirrup, large
enough to accommodate optionally several cups and several
frames;
FIG. 11 is a vertical section, partly broken away, through a
modified bottom plate of the stirrup of FIG. 10; and
FIG. 12 is a somewhat schematic vertical sectional view showing the
arrangement of the inventive receptacle holder, mounted in a
centrifuge drum, with a photo-electric transducer and a stroboscope
lamp flanking the flight path of the specimen containers.
As can be seen from FIGS. 1 and 6, the inventive receptacle holder,
in its exemplary, preferred embodiment consists essentially of
three major parts, namely a substantially U-shaped stirrup 1, with
a bottom plate 2 and journal pins 3 at the ends of shanks 4, a cup
5 and a receptacle support frame 6. Specimen containers, for
example test tubes 50, cam be inserted in the frame 6, as will be
explained later in full detail.
In the exemplary embodiment, the two stirrup shanks 4 are attached
(for example welded) about midway along the side edges of the
bottom plate 2. The two oppositely arranged shanks 4, thus
connected to the plate 2, constitute the U-shaped stirrup, when
viewed from the front (see also FIG. 3 for a modified stirrup
construction).
The cup 5 is preferably made from a plastic material with
relatively thin side walls and a thin bottom. The cup is shaped so
that it can be inserted and located on the plate 2, between the
stirrup shanks 4 (see FIG. 6). In order to secure the cup 5 against
unwanted movement in the direction of the double arrow 7 (FIG. 1,
lower section) the two opposite side walls 8 and 9 of the cup 5 are
provided with respective indentations or depressions 10 adapted in
their form to that of the shanks 4. FIG. 6 shows how the latter are
located within the depressions 10 when the cup 5 is assembled with
the stirrup 1.
The sectional detail view of FIG. 2 shows how the indentations 10
are profiled or shaped, e.g. by molding, when the cup 5 is made
from plastic. It will be understood that the indentations could be
provided in a different manner, and of course locating means other
than the mating shanks and indentations could be provided in the
cup and the stirrup, respectively.
The cup 5 is provided to receive the support frame 6; this means
that the outer shape of the latter is adapted and closely
corresponds to the inner shape of the former.
The receptacle support frame 6 consists essentially of a
square-shaped hollow member with windows or apertures 11 in its
side walls, as shown in the upper section of FIG. 1. It has a
bottom 12 and a sturdy head portion 13, the latter being provided
with a plurality of perpendicular through bores 14, preferably
arranged in several rows, adapted to receive and hold the
above-mentioned test tubes 50 and the like. The latter have usually
rounded bottom ends which rest on a soft insert 16 placed atop the
bottom 12, inside the frame 6 (see FIG. 2, not shown in FIG.
1).
For the purpose of centrifuging sediments or other substances in
the test tubes 50, the latter are placed into the frame 6 which is
then inserted in the cup 5, both being subsequently placed into the
stirrup 1. The inventive receptacle holder, in its assembled
condition, thus consists of the major parts 1, 5 and 6 which can be
pivotally inserted, by way of the journal pins 3, in a conventional
centrifuge head 57, as schematically shown in FIG. 7. Further
details of the head have been omitted since they are well known
from centrifuges.
FIG. 7 shows that the head 57 has a number of recesses 58,
preferably arranged in a symmetrical manner, 3 or 4 in a circular
arrangement, each recess being flanked by cut-outs 59.
Upon completion of the centrifuging process, the operator can
remove from the centrifuge head 57 either the entire receptacle
holder, that is stirrup 1, cup 5 and frame 6, or perhaps only the
cut 5 with the frame 6 therein, or even the latter (frame) by
itself, with the test tubes 50 therein. Another unit, assembled cup
or frame can be inserted with test tubes containing substances that
should be subjected to the next centrifuging operation.
The operator can observe the test-tube contents at any time through
the windows 11 in the side walls of the frame 6, before, during and
after centrifuging, without requiring the individual containers to
be removed from the support frame 6.
FIGS. 3, 4 and 5 show a modification in the form of a stirrup 1',
consisting of a single saddle member bent to U shape, having shanks
4' and a bridge portion 20 on which a bottom plate 2' (similar to
plate 2) can be secured by means of screws 22 and the like.
In order to secure plate 2' with respect to the stirrup 1', it may
be provided with lateral cut-outs 23, as shown in FIG. 5, for
clearing the shanks 4'. Additionally, a groove 24 may be provided
at the bottom of plate 2' (see FIG. 4) so that both the bridge
portion 20 and the shanks 4' are held in a form-fitting manner. The
ends of shanks 4' have riveted or otherwise secured journal pins
3', similar to the earlier-described pins 3, actually constituting
fastening means between the shanks and the pins.
The modified stirrup 1' of FIGS. 3 to 5 is of course
interchangeable with stirrup 1 of FIGS. 1 and 6, and it eliminates
the use of welding steps. Only two parts are needed, namely the
U-shaped, bent element and the bottom plate, as illustrated.
A further modification of the stirrup for the inventive receptacle
holder is shown in FIG. 10, generally designated 1". In a manner
similar to FIGS. 3 to 5, the stirrup proper is bent from flat
material, as shown, and a bottom plate 2" is secured with screws 22
to a horizontal bridge portion 27 between shanks 4". The latter
have respective pins 3" thereon, these parts of course
corresponding to the earlier described parts 4, 4' and 3, 3',
respectively.
The stirrup 1" is so designed as to be adapted to receive four
smaller receptacle support frames, such as frame 6 of FIGS. 1 and
6, within a rectangular girdle member 30, and resting on the bottom
plate 2".
FIGS. 8 and 9 show how four frames 6 can be simultaneously disposed
in respective one or more cups which are inserted in the stirrup
1". As a first solution, reference should be had to FIG. 8 which
shows four cups 5 each with its own frame of appropriate size,
inserted together in the stirrup 1" and held therein by the girdle
member 30.
The sectional detail view of FIG. 11 shows how to provide the
bottom plate 2" of stirrup 1" with a trough or rim 31, releasably
secured thereto by means of screws and the like. FIG. 10
illustrates ledges 32, extending partly or all along the
peripheries of the plate 2", for safely holding the cup or cups in
the stirrup.
Coming back to the afore-mentioned FIG. 9, another solution is
illustrated for lodging several frames 6 in a stirrup, such as 1"
as shown in FIG. 10, having four receptacle support frames 6 in a
common cup 5" which is thus four times as large, as a matter of
example, as the cup 5 of FIGS. 1, 6 and 8. It should be noted at
this point that in the modified embodiment of FIGS. 8 to 10, there
is no need for the locating means 8, 9 and 10, as described for the
first exemplary embodiment, on account of the provision of the
rectangular girdle member 30 although the sole or common cup 5"
could have indentations or depressions which cooperate with the
shanks 4" of stirrup 1", thus dispensing with the need for the
number 30. The shanks and pins have been omitted from FIG 9 for the
sake of clarity while they are shown in FIG. 8.
It is of course possible to design a support frame which fits
snugly into the cup 5- and contains four times as many test tubes
as the frame 6 of the standard embodiment. Although measurements
and proportions are not considered to be conclusive, for the sake
of comparison it might be considered that stirrup 1" is about four
times as large in its overall surface and receiving area as
stirrups 1 and 1', with similar proportions prevailing between the
respective cups and frames (e.g. 5" and 5).
The stirrup 1" of FIG. 10 having a larger space requirement, it
should be suspended from a centrifuge head similar to head 57 as
shown in FIG. 7, basically constructed for the stirrups 1 and 1'.
In a larger centrifuge, an appropriately dimensioned and designed
centrifuge head would be used to accommodate the fourfold capacity
of stirrup 1", as will be understood by those skilled in the
art.
There is nevertheless the advantage that the standard cups 5 and
frames 6 can also be used in the larger stirrup 1", one each of the
cups and frames fitting the stirrup 1 and 1" while four will be
needed for 1". Similar structures could of course be designed for a
smaller or larger number of elements (say three or six cups or
frames, with a corresponding number of test tubes to be lodged
therein for simultaneous processing).
FIG. 12 is a somewhat schematic partial, vertical sectional view
through a centrifuge drum 55 which has a cover 56 closed during
centrifuging. The inventive receptacle holder, consisting as it
does of a stirrup 1 (1' or 1"), cup 5 (or 5") and frame 6 (or a
modification of the latter), fitted with a number of test tubes 50,
is shown in this figure in its flight path, assumed during
high-speed centrifuging (the device swings outward on account of
the centrifugal force, about the pins by which it is attached to
the centrifuge head 57).
The cup 5 is made preferably from plexiglass, making it perfectly
transparent, so that the windows or apertures 11 of the frame 6
allow the ends of the test tubes 50 to be visible at all times.
Above the area where the apertures 11 pass during the rotation of
the unit, the cover 56 or other structure of the centrifuge drum
may have a photo-electric transducer or sensor 17 disposed therein.
Substantially perpendicularly below, the drum has a stroboscope
lamp or other source 18 disposed, with a pulse frequency adapted to
the rotational speed of the head 57 and/or the number of the
receptacle holders in the device.
The adaptation of the pulse frequency of the lamp 18 is
accomplished, for example, by providing a conventional pulse
emitter, such as shown in FIG. 12 at 19a and 19b, in cooperation
with a driven shaft or shaft extension of the centrifuge motor,
schematically shown at 53. With each revolution of the centrifuge
head 57, photo-electric or other pulse producing means in unit 19a
gates a pulse generator unit 18a which in turn controls the
flashing frequency of the lamp 18.
The photo-electric unit 17 may include two photocells or two groups
thereof, as 17a and 17b. One of these can be chosen to respond to
the light - dark jump in the change of transparency of the
substances within the terminal portions of the test tubes 50, and
the other is further inside (toward the axis of rotation of the
centrifuge head), scanning intermediate portions of the test tubes.
It is known that during centrifuging thickened sediments such as
schematically shown at 51 settle in the ends of the test tubes
while clear liquid 52 remains above the sediments, that is further
inside toward the rotational axis.
The photocell or group 17b responds to the dark - light jump which
occurs in the course of centrifuging by the settling of the
sediments and the clarification of the liquid thereabove. In this
manner the response sensitivity of the photo-electric unit 17 can
be substantially increased. The electrical parameters obtained by
way of the photocells or groups 17a, 17b can be combined or
integrated into a single control signal, such as by using known
electrical or electronic circuits, for example an AND-type logic
gage and the like.
The above arrangement allows it to determine the duration of the
centrifuge process by the centrifuging effect itself, the signal
derived from the photo-electric unit 17 serving to stop the
centrifuge through conventional electrical circuit and switching
means, schematically shown at 17c.
It should be understood, of course, that the foregoing disclosure
relates only to preferred embodiments of the invention, and that it
is intended to cover all changes and modifications, as well as the
combination of separately shown features, which do not constitute
departures from the spirit and scope of the invention.
* * * * *