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Simple adapter for facilitating comparation of ultracentrifuge plates
490
SHORT COMMUNICATIONS NORMAND L. FORTIER JOHN SILVA~ FABIAN J. LIONETTI
Division of HematologicResearch Institute for Health Sciences Brown University, Providence, Rhode Island 02912 Received August 16, 1968
‘Fellow of the PHS training program at Providence College (5-Tl-GM-454), Providence,
Rhode Island.
Simple
Adapter
for Facilitating Ultracentrifuge
Comparation
of
Plates
Many measurements made with comparators require subsequent subtraction of one reading from another. This is usually the case with the plates on which ultracentrifuge patterns are recorded. However, Trautman (ref. 1) has incorporated a special stage in his comparator so that this and other arithmetic can be avoided, by making it possible to set the micrometer reading to any desired value after the cross-wires have been brought into coincidence with the reference mark on the photographic image, For measurement of schlieren patterns manual positioning of the plate on the comparator stage can be done easily, but for interference fringe measurements plate orientation is much more critical. The simple device shown in Figure 1 which, when attached to a standard twodimensional comparator achieves virtually the same objects as Trautman’s specially constructed comparator, has been used successfully for some time. Figure 2 shows the device fixed to the carriage of a comparator (supplied by Precision Grinding Corporation Ltd., Mitcham Junction, Surrey), and Figure 3 is a diagram of the relevant parts of the comparator, with adapter attached. The adapter consists basically of a wedge block (1) screwed to the comparator carriage (2) and a second wedge block (3) suspended so that8 its wedge face can slide across the corresponding face of the first block. The two wedges are maintained in contact by the return spring of the comparator carriage which keeps the movable wedge in contact with the micrometer spindle (4). A rack (5), which is attached to the fixed block parallel with its wedge face, engages with an idler pinion (6) supported
SHORT
491
COMMUNlC4’i’IONS
5cm.
?
I
\
-I-
‘e
J
8
b
SECTION
ON’A-A’.
FIG. 1. Details of construction of comparator adapter: plan view (a), end view (b), section (c), fixed wedge (l), comparator carriage (2), movable wedge (3), micrometer spindle (4), rack (51, pinion (6), worm (7), knob (S), small bracket (9): angle bracket (IO), slot (ll), large-headed screw (12), spacer (13).
on the other block. Also meshing with the pinion is a worm (7) that has an extended spindle terminating in a knurled knob (8). The worm is supported by small brackets (9) fixed to the top of the movable wedge: which is suspended from an angle bracket (10). The latter, which is attached to the carriage by the same screws as block 1, has a slot (11) cut parallel with the wedge faces of the blocks. The shank of a large-headed screw (12) is a sliding fit in this slot, and the screw is locked into the movable wedge, although both pinion (6) and spacer (13) are free to
492
FIG. 2. riage (2), (7), small (14), and
Adapter movable bracket rotatable
attached to comparator, showing fixed wedge (l), comparatt )r carwedge (3)) micrometer spindle (4), rack (5), pinion (6), worm (9), angle bracket (lo), large-headed screw (12), micrometer drum stage (16).
FIG. 3. Position of adapter relative to comparator. Diagram, not to scale, shows comparator carriage (Z), micrometer spindle (4), worm (7), knurled knob (8), angle bracket (lo), micrometer drum (14), ultracentrifuge plate (15), rotatable stage (16), reference mark (177, reference fringes (18, 19).
SHORT
493
COMMUNICATIONS
turn on the shank. The thickness of the wedge blocks is such that they just clear the bed on which the comparator carriage slides. In use, the drum (14) of the micrometer is set to read zero, or, in the case of ultracentrifuge patterns, some even more useful reference reading (see below). The plate (151 is clamped to the comparator stage and manually adjust’ed until the horizontal reference mark (17) on the plate appears close to the intersect.ion of the cross-wires in t,be projection viewer (not shown). The rotat,able stage (16) is used to align the reference fringes (IS, 19) as accurately as possible with the longitudinal movement of the carriage. Then rotation of the worm causes the movable wedge to slide across the other, shifting the carriage a very small distance longitudinally so that the image of the horizontal reference (17) is exactly coincident wit,h the intersection of the cross-wires. All micrometer readings subsequently taken are then absolllte on thr scale of the plate. The value, x,, at, which the micrometer drum ought to be set initially for this to hold is calculated by multiplying the magnification factor of the ultracentrifuge optical system (in the appropriate direction) by the real distance of the reference from the axis of rotat’ion of t,he rotor. Because s,. exceeds the drum range, an integral number of cm is subtracted from 5, to give the setting, and is added mentally to all readings, e.g., if Z, = 2.124 X 5.70 cm = 12.1068 cm the drum is set to read 0.1068 cm when the crosswires coincide with the rcafrrcncc and 12 cm is added to each reading. The dimensions of the adapter show-11 arc convenient, but could well be different without disadvantage. The two factors governing the sensitivity of the adjustment arc the wedge angle of the blocks (tan-l 0.025 in the assembly shown) and the number of teeth per miit length of rack (20 per inch in this case). For a rotation of about 111/!,” of t’he knurled knob these correspond to a carriage movement of 0.0001 cm, the limit of mea,surement on the micrometer. Accuracly of fit of components appears not to be very critical, and it is easily verified that any slack in the system has been taken up if the carriage is pulled slightly to the left and its return spring allowed to pre,,qq blocks and micrometer spindle together. The image of the horizontal reference (17) should remain coincident with t,he cross-wires. If not, a second adjustment is made by rotating the worm and rechecking. ACKNOWLEDGMENTS The author thanks for the drawings.
Mr.
S. Grmsw~ll
for
helpful
RP;FERENClS 1. TR4UTM.4N.
R., 2. Ph~n.
Chem.
60, 1211 (1956).
suggestions
and
Mr.
F. .4. New
494
SHORT
COMMUNICATIONS
1’.
The National Institute for Medical The Ridgeway, Mill Hill London N.W.7, England Received August 21, 196S
Volumes
GHARLWOOD
Research
Device for Automatically Eluting Buffer after Sample
A.
Starting Application
to Chromatographic
the Flow of of Large Columns
When applying a large volume of sample to a chromatographic column, it is sometimes rather difficult to complete the sample application and start the eluting solvent at a time of day which is convenient. To eliminate this inconvenience, we have used the arrangement shown in Figure 1.
Sample Reservoir
Approx 2 Feet Buffer Reservoir
FIGURE
I
SHORT COMMUNICATIONS NORMAND L. FORTIER JOHN SILVA~ FABIAN J. LIONETTI
Division of HematologicResearch Institute for Health Sciences Brown University, Providence, Rhode Island 02912 Received August 16, 1968
‘Fellow of the PHS training program at Providence College (5-Tl-GM-454), Providence,
Rhode Island.
Simple
Adapter
for Facilitating Ultracentrifuge
Comparation
of
Plates
Many measurements made with comparators require subsequent subtraction of one reading from another. This is usually the case with the plates on which ultracentrifuge patterns are recorded. However, Trautman (ref. 1) has incorporated a special stage in his comparator so that this and other arithmetic can be avoided, by making it possible to set the micrometer reading to any desired value after the cross-wires have been brought into coincidence with the reference mark on the photographic image, For measurement of schlieren patterns manual positioning of the plate on the comparator stage can be done easily, but for interference fringe measurements plate orientation is much more critical. The simple device shown in Figure 1 which, when attached to a standard twodimensional comparator achieves virtually the same objects as Trautman’s specially constructed comparator, has been used successfully for some time. Figure 2 shows the device fixed to the carriage of a comparator (supplied by Precision Grinding Corporation Ltd., Mitcham Junction, Surrey), and Figure 3 is a diagram of the relevant parts of the comparator, with adapter attached. The adapter consists basically of a wedge block (1) screwed to the comparator carriage (2) and a second wedge block (3) suspended so that8 its wedge face can slide across the corresponding face of the first block. The two wedges are maintained in contact by the return spring of the comparator carriage which keeps the movable wedge in contact with the micrometer spindle (4). A rack (5), which is attached to the fixed block parallel with its wedge face, engages with an idler pinion (6) supported
SHORT
491
COMMUNlC4’i’IONS
5cm.
?
I
\
-I-
‘e
J
8
b
SECTION
ON’A-A’.
FIG. 1. Details of construction of comparator adapter: plan view (a), end view (b), section (c), fixed wedge (l), comparator carriage (2), movable wedge (3), micrometer spindle (4), rack (51, pinion (6), worm (7), knob (S), small bracket (9): angle bracket (IO), slot (ll), large-headed screw (12), spacer (13).
on the other block. Also meshing with the pinion is a worm (7) that has an extended spindle terminating in a knurled knob (8). The worm is supported by small brackets (9) fixed to the top of the movable wedge: which is suspended from an angle bracket (10). The latter, which is attached to the carriage by the same screws as block 1, has a slot (11) cut parallel with the wedge faces of the blocks. The shank of a large-headed screw (12) is a sliding fit in this slot, and the screw is locked into the movable wedge, although both pinion (6) and spacer (13) are free to
492
FIG. 2. riage (2), (7), small (14), and
Adapter movable bracket rotatable
attached to comparator, showing fixed wedge (l), comparatt )r carwedge (3)) micrometer spindle (4), rack (5), pinion (6), worm (9), angle bracket (lo), large-headed screw (12), micrometer drum stage (16).
FIG. 3. Position of adapter relative to comparator. Diagram, not to scale, shows comparator carriage (Z), micrometer spindle (4), worm (7), knurled knob (8), angle bracket (lo), micrometer drum (14), ultracentrifuge plate (15), rotatable stage (16), reference mark (177, reference fringes (18, 19).
SHORT
493
COMMUNICATIONS
turn on the shank. The thickness of the wedge blocks is such that they just clear the bed on which the comparator carriage slides. In use, the drum (14) of the micrometer is set to read zero, or, in the case of ultracentrifuge patterns, some even more useful reference reading (see below). The plate (151 is clamped to the comparator stage and manually adjust’ed until the horizontal reference mark (17) on the plate appears close to the intersect.ion of the cross-wires in t,be projection viewer (not shown). The rotat,able stage (16) is used to align the reference fringes (IS, 19) as accurately as possible with the longitudinal movement of the carriage. Then rotation of the worm causes the movable wedge to slide across the other, shifting the carriage a very small distance longitudinally so that the image of the horizontal reference (17) is exactly coincident wit,h the intersection of the cross-wires. All micrometer readings subsequently taken are then absolllte on thr scale of the plate. The value, x,, at, which the micrometer drum ought to be set initially for this to hold is calculated by multiplying the magnification factor of the ultracentrifuge optical system (in the appropriate direction) by the real distance of the reference from the axis of rotat’ion of t,he rotor. Because s,. exceeds the drum range, an integral number of cm is subtracted from 5, to give the setting, and is added mentally to all readings, e.g., if Z, = 2.124 X 5.70 cm = 12.1068 cm the drum is set to read 0.1068 cm when the crosswires coincide with the rcafrrcncc and 12 cm is added to each reading. The dimensions of the adapter show-11 arc convenient, but could well be different without disadvantage. The two factors governing the sensitivity of the adjustment arc the wedge angle of the blocks (tan-l 0.025 in the assembly shown) and the number of teeth per miit length of rack (20 per inch in this case). For a rotation of about 111/!,” of t’he knurled knob these correspond to a carriage movement of 0.0001 cm, the limit of mea,surement on the micrometer. Accuracly of fit of components appears not to be very critical, and it is easily verified that any slack in the system has been taken up if the carriage is pulled slightly to the left and its return spring allowed to pre,,qq blocks and micrometer spindle together. The image of the horizontal reference (17) should remain coincident with t,he cross-wires. If not, a second adjustment is made by rotating the worm and rechecking. ACKNOWLEDGMENTS The author thanks for the drawings.
Mr.
S. Grmsw~ll
for
helpful
RP;FERENClS 1. TR4UTM.4N.
R., 2. Ph~n.
Chem.
60, 1211 (1956).
suggestions
and
Mr.
F. .4. New
494
SHORT
COMMUNICATIONS
1’.
The National Institute for Medical The Ridgeway, Mill Hill London N.W.7, England Received August 21, 196S
Volumes
GHARLWOOD
Research
Device for Automatically Eluting Buffer after Sample
A.
Starting Application
to Chromatographic
the Flow of of Large Columns
When applying a large volume of sample to a chromatographic column, it is sometimes rather difficult to complete the sample application and start the eluting solvent at a time of day which is convenient. To eliminate this inconvenience, we have used the arrangement shown in Figure 1.
Sample Reservoir
Approx 2 Feet Buffer Reservoir
FIGURE
I