Five- Port Mechanically Operated ElectricaIIy Controlled Valve Paul B. Hamilton, Alfred 1. du Pont Institute, Wilmington, Del.
livery tip of the plug is straight and is provided with an expanded portion to prevent attached rubber tubing from slipping off. The side arms of the stopcock are bent vertically and terminate in female SB 12/5 joints. To clear the motor, the arm protruding beneath it is bent, horizontally forward for approximately 1 inch, and then vertically. The driving mechanism is built as a demountable unit which can be readily detached from the stopcock frame by removing two knurled screws, K , K . This enables the stopcock to be easily and rapidly serviced or replaced. With the driving unit in place, the control knob of the plug is engaged in the driving cup, D, a t the bottom of the vertical shaft, V . I n Figure 1 slots in the driving cup engage a brass pin through the control portion of the Teflon plug. With glass plugs, the more conventional symmetrical knob is held by a cup designed to receive it. The gear, G, a t the top of the vertical shaft is engaged by the worm, W (G1023 gear, HLSH worm, ratio 100 to 1, Boston Gear Works, Quincy, Mass.), mounted on the horizontal shaft, H . The latter is coupled, J,directly to the output shaft of the helical-gear reducer motor, M (B8194E-30Ml 56 r.p.m., Bodine Electric Co., 2254 West Ohio St., Chicago 12, Ill.). The motor is connected electrically for clockwise rotation. Mounted on the vertical shaft between gear and cup are two cams for activating the control switches. The upper cam, C1, is bolted to the gear; the lower cam, Cz, has its own hub and setscrew for locking to the
Stein, and Moore (3) and S Hamilton (1, 2) have shown, in the chromatography of amino acids on PACKMAY,
0.9 X 100 or 150 cm. analytical ion exchange columns, that flow through the columns can be elevated to rates as high as 35 ml. per hour (55 ml. per square em. per hour) under the conditions of analysis which these authors have described. With such rapid flow rates, it is often imperative to change solutions a t nonworking times of the day, in order to keep the specified schedules when a sequence of buffers is employed in column development. To affect solution changes a t any time, the five-port mechanically operated, electrically controlled valve described was devised. Because of the possibility of wider application, the essential details of the valve are described and illustrated in Figure 1. A four-way borosilicate glass stopcock with arms 90" apart and in the same plane (Scientific Glass Apparatus Co., Inc., Bloomfield, K. J., catalog J-2213-lJST17) is mounted in an aluminum frame, F, where it is retained by a plastic ring, R. Plastic screws, S,in the ring enable play of the arms to be eliminated without strain. A modified Fresenius-type plug, PL, without a slot in the barrel opposite the bore, may be fabricated either of borosilicate glass or Teflon and should have a symmetrically shaped control knob that can be easily coupled to the turning mechanism. Teflon plugs should be spring-loaded as s h o m . The de-
shaft. The upper cam bears four elevations 90" apart on its edge; the lower cam bears four half-round grooves also 90" apart on its edge. The control switches, SI, S2 (ISM1 subminiature, with JS-5 roller actuator, Microswitch Co., Freeport, Ill.), are each mounted on circular plates, PI, P,,which rotate freely on the vertical shaft belom each cam. The plates pass through slots in the plate block, PB, where each may be independently locked by screws, L, L: They are also provided 15 ith two slotted holes (not shown) for bolting the snitches in position. The cams and snitches are adjusted as follovrs: Clockwise rotation of the motor results in clockwise rotation of the vertical shaft (when viewed from abore) and hence clockwise rotation of both cams. K i t h cam C1 locked to the shaft through the gear, cam Cz is rotated clockwise until its grooves lie approximately 20" ahead of the elevations on the upper cam; it is then locked in place on the shaft. The lower plate, Pz, is rotated so that the actuator roller of its switch, S,,lies in one of the grooves; it is locked in position a t the block. The upper plate, P I , is rotated so that the roller of its switch, SI, lies on its cam approximately half the angular distance between the cam elevation and the position of the lower cam groove (projected vertically on the upper cam). The plate is locked a t the block in this position. Finally, the subminiature switches are adjusted on their respective plates. The upper switch is shifted on the slotted holes, so that it will remain open except for the momentary closure which takes place when an elevation passes the roller as the cam rotates. The lower switch is adjusted, so that it is open when its roller rests in a cam groove and closed when it rises out of the groove as the cam rotates. After
4 Figure 1. of valve
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Essential details
XSIGNALX ' INPUT i
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Figure 2. Electrical connections
1
IIOV
zc
VOL. 30, NO. 1 1 , NOVEMBER 1958
1887
satisfactory adjustment, the srvitches are bolted securely in position. Electrical connections are shonn in Figure 2 . Switches S1, Sz, and the latching relay switch, RS, are all wired for normally open operation. A cycle of operation is as follons. A momentary electrical impulse from the governing mechanism-e.g., a Technicon fraction collector-to the control coil (signal input a t SX) of the latching relay (LE 2C l l X A , -1dvance Relay, Electronics Division, Elgin K a t c h Co., Burbank, Calif.) mol-es the armature which locks and simultaneously closes the relay snitch RS. This completes one circuit to the motor, nhich then turns. Rotation of can1 CB lifts the roller from the groove to close S2, which completes a parallel motor circuit. As rotation continues, the elevation on cam C1, which passes the roller of Si, momentarily closes the circuit to the reset coil. thereby unlocking the
relay and opening switch RS. Power to the motor is maintained through S2 until its roller drops in the next cam groove, causing the motor circuit to be broken. Because the stopcock turns s l o d y , 90” in 45 seconds, and because of its frictional resistance there is no rotational momentum; on breaking the motor circuit, dead stop arrest of the plug occurs. At the completion of a cycle, the apparatus is ready for the next, on impulse from the controlling apparatus. K i t h the device, four diffuent solutions may be delivered in succession through the side arms of the valve to the conimon exit from the plug, and solution changes may be effected a t any time on signal from the controlling apparatus. Fluid dead space, from plug to apparatus being supplied, is of constant volume and unirrigated cul-desacs do not contribute to the dead space.
Detailed mechanical drawings are available on request. ACKNOWLEDGMENT
The author gratefully acknowledges the assistance of E. R. Rohrbaugh, Model Machine Co., 1129 Capitol Trail, Xewark, Del., with design, development, and complete fabrication of the unit. LITERATURE CITED
(1) Hamilton, P. B., ANAL. CHEAT. 30, (2) Hamilton, 914 (1958). P. B., in “Ion Exchangers
in Organic and Biochemistry,” Calmon and Kressman, ede., Chap. 14. D. 280. Interscience. SeF- Tork. 195j.
(3) Spackman, D. H., Stein, IT. H., Xoore, S., Federation Proc. 15, 358 (1956).
Adapter for Utilization of Pen and Ink Recorder with Polarograph Truman
s.
Licht, David J. Curran, and Andre J. deBethune, Department of Chemistry, Boston College, Chestnut Hill 67, Mass.
RECORDING potentiometer may A adapted to convert a manual
be or photographic polarograph into an automatic pen and ink recording polarograph with direct-reading current and voltage scales. Problems encountered in this adaptation include maintaining recorder sensitivity, facilitating shifting and expansion of the voltage axis, and damping of mercury drop oscillations. These problems have been solved with the circuit shonn in the figure in conjunction n-ith a Sargent Model XI1 photographic polarograph as a motordriven voltage source, and a Brown 0-10 niv. recording potentiometer. However, any linear motor-driven sliden-ire nhich may be set to span the voltage range from 0 to 3 volts in 10 to 15 minutes, may be employed as a voltage source. Many suitable recorders are available [G. W.Em-ing, J . Chem. Educ. 33, 424 (1966)l. The numerical values belom- apply to the above polarographrecorder combination. I n its simplest form, constructed by omitting the portions of the figure in dotted lines, the only parts needed are: R1,a 0- to 10,000-ohm decade resistance box; RP,a 3800-ohm resistor; RI, a 25ohm variable resistor; B,, a 1.5-volt flashlight battery, and switch Sl. If desired, a combination wave spreader and voltage zero shifting circuit may be added by inserting, at X Y , a 150-ohm variable resistor, Rq, a 1.5-volt battery, BP,like Burgess KO. 6, and switch SZ.A suitable damping circuit may be added with C1 and Cz, a pair of 2000-pf. 15voIt direct current condensers and slyitch Ss. By selection of R1 and of the voltage span setting, the chart voltage and time 1888
ANALYTICAL CHEMISTRY
scales may be converted into directreading polarographic current and voltage scales, respectively. Values of Ri and of voltage span should be calculated from the voltage-time characteristics of each recorder-slide-11-ire combination. For example, with a 0-10-mv. recorder and 280-mm. chart, an R1 setting of 1191 or 357.1 ohms gives 0.03 or 0.10 pa. per mm., and allons full scale currents of 8.4 or 28.0 pa., respectively. If a full span of the motor-driven slidenire covers 85.5 chart time units, a voltage span setting of 0.855 or 2.57 volts would then give 0.01 or 0.03 volt per chart time unit, respectivelv. The use of the voltage shifting portion of the circuit may be illustrated as foll o w . If the X Y roltage is 0.20 volt (X negative), the voltage scale, which might originally have spanned from 0 to -1.70 volts, would be shifted to span from +0.20 to -1.50 volts. By reversing the polarity of battery Bz, the same portion of the circuit may be used as a wave spreader [as described by D. S . Hume and T. IT. Gilbert, ANAL. C H m r . 24, 431 (1952)]. Thus it would _i
be possible to have a full scale Ecanning between any tn-o voltages. ‘C‘se of good quality variable resistors in R3 and R4. such as the spiral-wound Beckman Helipot. will increase the smoothness of operation of zeroing coiltrols. A constant-speed drive motor for the slide-wire is desirable; this type of motor is not used in the Sargent Model XII. If the Model XI1 is used, the galvanometer may be safeguarded by setting the sensitivity control a t 1000, or it may be clamped, or shorted. The circuit can be checked by substituting a precision resistor of 100,000 ohms for the cell, and verifying that the plot of Ohm’s law obtained on the recorder is correct within 1% of the full scale voltage and current. ACKNOWLEDGMENT
Grateful acknowledgment is made to
B. TI7. ST’essling (hI. S. thesis 1955, Boston College) for an earlier design of this adapter and to the International Kickel Co. for a grant-in-aid in support of this n-ork.
