US2990257A

US2990257A - Zone refiner

Info

Publication number: US2990257A
Application number: US692667A
Authority: US
Inventors: Heneage Peter; Billy W Taylor
Original assignee: Fisher Scientific Co LLC
Current assignee: Fisher Scientific Co LLC
Priority date: 1957-10-28
Filing date: 1957-10-28
Publication date: 1961-06-27
Anticipated expiration: 1978-06-27

Description

June 27, p HENEAGE ET AL 2,990,257

ZONE REFINER Filed Oct. 28, 19-57 3 Sheets-Sheet 1 Fig. Fig. 2

INVENTORS. Peter Heneage Bil/y M. Taylor THE IR A TTORNE Y5 June 27, 1961 P. HENEAGE ETAL 2,990,257

ZONE REFINER Filed Oct. 28, 1957 3 Sheets-Sheet 2 Fig. 3

INVENTORS. Peter Heneage Bil/y M. Taylor BY m Z/o rm m THE /R A T TORNE YS June 27, 1961 HENEAGE AL 2,990,257

ZONE REFINER 3 Sheets-Sheet 3 Filed Oct. 28, 195'? Fig.6

Peter Heneage Bil/y W. Taylor Fig 7 I Z k ,m

THE IR ATTORNEYS United States Patent 2,990,257 ZONE REFINER Peter Heneage and Billy W. Taylor, Pittsburgh, Pa., as-

signors to Fisher Scientific Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 28, 1957, Ser. No. 692,667 Claims. (Cl. 23-273) This application relates to a zone refiner, more specifically to apparatus for carrying out the known laboratory technique of zone refining which is used by chemists or others desiring materials of very high purity.

In practicing the technique of zone refining, a sample of the material to be tested is placed in an elongated container of suitable material and having a small cross-sectional area relative to its length. A suitable container is an elongated glass tube which may have any shape in cross section, such as round, square, oval, etc. Increments of the sample are heated progressively in the tube along the length of the tube so that a narrow molten zone passes continuously through the sample in the tube. As the molten zone passes through the sample, it carries along with it impurities in the sample. The molten zone may be passed through the sample as many times as desired to obtain the purity desired. After several passes, the sample is relatively pure at one end and the impurities are concentrated in the other end.

Our zone refiner enables a person to perform the technique of zone refining more accurately and at the same time more easily than has been possible with equipment heretofore available. Our zone refiner provides very close control over the speed of movement of the molten zone through the sample and very close control over the size of the molten zone. Our instrument can be set to cause a molten zone to pass through the sample in either direction along the length of the sample.

The operation of the instrument does not require the chemists constant attention. After a container of a sample to be refined is installed in our zone refiner, the instrument can be set to make a single pass through the sample at any speed desired, and it will stop automatically at the end of the pass. If a multiple pass operation is desired, the instrument can be set to repeat the passes automatically.

In order to cause a molten zone to pass through the sample to be refined, we provide a support for the tube containing the sample and we provide a small heater which is positioned adjacent to the tube and which is of such size as to melt a small increment of the length of the sample in the tube. The heater is moved along the length of the tube and adjacent to the tube so that the molten zone created by the heater passes longitudinally through the sample. Preferably, we provide a cooler spaced longitudinally from the heater and following the heater, which cools the portion of the sample which has been melted after the heater has moved from that portion. The heater and cooler are both mounted on a carriage which moves slowly in one direction during the heating and cooling cycle. At the end of the sample in the tube, the carriage is returned rapidly to the other end and the process is repeated until the desired purity is obtained.

In the accompanying drawings, we have illustrated a presently preferred embodiment of our zone refiner, in which:

FIGURE 1 is a front elevation of our refiner;

FIGURE 2 is a side elevation with a side panel of the refiner open;

FIGURE 3 is an enlarged front elevation (partially in section) of the carriage for supporting the heaters and coolers of our zone refiner;

FIGURE 4 is a section along the lines lV-IV of FIGURE 3;

FIGURE 5 is a section along the lines VV of FIG- URE 3;

FIGURE 6 is an electrical diagram showing the electrical circuits used in our refiner;

FIGURE 7 is a partial elevation View of mechanism for oscillating the tube about its longitudinal axis; and

FIGURE 8 is a partial elevation view of mechanism for oscillating the tube longitudinally.

Our zone refiner is contained in a sheet metal housing 9 mounted on a base 10 and having a front panel 11. The front panel is divided longitudinally by a V-shaped bend 12 to provide a control panel 13 and an operating panel 14.

Mounted in front of the operating panel 14 is a support rod 15 which supports a glass tube 16 containing the sample to be refined. The support rod 15 carries a bottom tube support 17 and a top tube support 18 which slide along the rod 15 and which may be held in any fixed position on the rod by set screws 19. The bottom tube support has a rod 20 threaded into its outer end which carries a tip 21 of heat resistant material on which the tube 16 rests. ledger binder posts which are threaded into each other end to end in the conventional manner so that the length of the rod can be adjusted. The top tube support is in the form of a ring which surrounds the upper end of the tube 16. Two thumb screws 22 and a spring loaded plunger (not shown) spaced equidistantly around the ring center the tube in the ring.

One or more heaters 23 and a corresponding number of coolers 24 are positioned adjacent the tube 16 and are caused to move back and forth along the length of the tube. The construction of the heaters and coolers is shown in FIGURES 3 to 5, inclusive. The heaters comprise a length of electrical resistance wire 25 which is wrapped around the tube 16 but spaced therefrom a sufficient distance to allow for free movement of the heater along the tube. Clamps 26 on the ends of posts 27 hold the ends of the resistance wire 25. The posts 27 extend through a slot 28 in the front panel 14 and, at their inner ends, they are mounted in carriers 29. A vertical post 30 supports the carriers 29, the carriers having vertical bores which fit around the post 30, and the carriers are held in any desired fixed position on the vertical post 30 by set screws 31. The rods 27 at their inner ends also have binding posts 32 for conductors 33 which supply heating current to the resistance wire 25.

The coolers 24 are in the form of a ring 34 which surrounds the tube 16 but which is spaced therefrom. The ring 34 has an inner circular passageway 35 and radial passageways 36 connected to the passageway 35 and directed inwardly towards the tube 16. A tube 37 supports the ring 34 and supplies air under pressure to the passageway 35, which air flows out through the passageways 36 against the outer surface of the tube 16. A carrier 38, similar to the carrier 29 for the heater, supports the tube 37. The carrier 38, in turn, is supported by the vertical rod 30 and its position on the rod may be adjusted by a set screw 39. Flexible tubes 37a connect the tubes 37 to an air supply manifold 48a, hereinafter described.

A carriage 40 supports the vertical post 30 and this carriage is driven to move the heaters 23 and the coolers 24 back and forth along the length of the tube 16. The structure of the carriage 4i and the mechanism for moving it will now be described. Within the cabinet 9 and back of the panel 14, there is a supporting framework comprising a bottom plate 41 and a top plate 42, both plates being secured to the cabinet. Two support rods 43 and a threaded drive shaft 44 extend between the bottom and

top plates

41 and 42. A third support rod (not shown) extends between the

plates

41 and 42 adjacent the The rod 20 is made up from a series of r 3 front of the plates and opposite to the rod 43 shown in FIGURE 2 which is adjacent the front of the plates.

The carriage 40 is a generally rectangular casting having a top member 45, a bottom member 46, and

cross members

47, 48, and 49. The top and

bottom members

45 and 46 have bores 43a through which one of the support rods 43 extends. The cross member 4? extends downwardly below the level of the member 46 and is bent outwardly toward the panel 14 to form a horizontal extension 49a into which the lower end of the post 3%} is threaded. The bot-tom member 46 has a bushing t) which is threaded to cooperate with the threads on the drive shaft 44. Rotation of the drive shaft 44' thereby raises or lowers the carriage 4f), the post 30, and the heaters and coolers. The cross member 48 is wider than the other members of the carriage 4i and is drilled to form an air manifold 45 a and cross passages 48b. Tubes 48c connect the cross passages 43!) and the flexible tubes 37a. The manifold 48a is supplied with air through a flexible hose 48d which leads to a suitable air connection 48:: outside the cabinet (see FiGURE 1).

During the heating and cooling pass, the heaters and coolers mounted on the carriage move at a slow rate of speed the length of the tube containing the material to he refined. At the end of the slow pass, the carriage is returned rapidly to the other end of the tube where a slow heating and cooling pass again starts. In our zone refiner, the slow heating and cooling pass can be carried on in either direction and the fast return pass is arranged to operate in a direction appropriate to the direction of the slow pass.

We also provide a driving mechanism and control circuit therefor whereby the speed of the heating and cooling pass can be adjusted. The circuit also includes means whereby the carriage can be automatically stopped at the end of a single heating and cooling zone or the cycle of a slow and fast pass can be continued indefinitely. We further provide a jog circuit whereby an operator can move the heaters and coolers to any desired position along the length of the tube.

The driving mechanism and electrical control circuit therefor are shown in FIGURES 2 and 6, FIGURE 6 being a diagram of the electrical circuit. As noted, the carriage mounting the heaters and coolers is driven by a shaft 44. The shaft is rotated by two motors, a slow motor 51 mounted on the plate 42 and a fast motor 52 mounted below the plate 41. The supply of current to these motors is controlled by a microswitch 53 which, in turn, is opened and closed When the carriage reaches its limits of travel at either end of a pass.

A control rod 54 is movable lengthwise in the supporting framework and carries two

trip levers

55 and 56 which may be positioned at any point along the length of the control rod and which are held in any selected position by thumb screws 57. The control rod also has two laterally extending arms 58 which engage actuating buttons on the microswitch 53 to open and close appropriate contacts.

When the carriage reaches the limit of its travel in one direction, as determined by the position of a

trip lever

55 or 56 on the control rod, it strikes the lever and this, in turn, moves the control rod in the direction of the movement of the carriage. Movement of the control rod causes one of the laterally extending arms 58 to engage the switch and shift it from one position to the other. The action of the switch 53 can be best understood from a description of the electrical circuit in which it forms a art.

p Referring to FIGURE 6, the circuit includes a plug 59 for connecting the instrument into a source of power and a manually operated main switch 60 for controlling the supply of current to the refiner and a fuse 61. The circuit also includes the fast motor 52, a switch 62 for jogging the carriage, a switch 63 by which automatic or one pass operation is selected, the switch 53, and a reversing switch 64, which is used to select the direction of the heating and cooling cycle. The circuit further includes the slow motor 51 and a proportional timer 65. Included in the slow motor and timer circuit are two step-down transformers 66 and 67 for supplying heating current to the heaters, the transformer 66 being variable so that the supply of current to the heaters can be adjusted by a knob 66a on panel 13. The circuit also includes a pilot light 68 for indicating when current is being supplied to the instrument when the main switch 60 is closed, a pilot light 69 which shows when the fast motor 52 is operating, a pilot light '76 which indicates operation of the slow motor 51, and a pilot light 71 which indicates when current is being supplied to the heaters.

The operation of the control circuit will now be described, assuming an operation in which it is desired to heat the material being refined on the down stroke of the heaters and coolers and further assuming that the i heaters and coolers are at the upper limit of their path of travel and are about to start the downward heating pass. The switch 60 is closed. The jog switch 62 is in neutral position, as shown in FIGURE 6. The limit limit switch 53 is in position to close the contact 72. The reversing switch 64 is in position to close the two pairs of contacts adjacent to the legend Down nearest the switch in the figure.

The switch 64, as stated, is a four pole, double throw switch. Two

poles

73 and 74 are used to control the direction of both the fast and slow motors. That is, if a down heating cycle is desired, then the two

poles

73 and 74 are connected to the two contacts adjacent the legend Down so that the slow motor is energized and drives the shaft 44 in a direction to move the heaters and coolers downwardly. When the heaters and coolers reach the lower limit of their path, then the two

poles

73 and 74 determine the direction of the fast motor so that, when it is energized, the heaters and coolers move rapidly in an upward direction. Conversely, if the

poles

73 and 74 are moved to close the contacts adjacent the legend Up nearest the switch, so that the material being refined is heated on an upward pass of the heaters and coolers, then, when the slow motor 51 is energized, it will drive the shaft 44 in a direction to slowly raise the heaters and coolers, and the fast motor, when it is energized, will drive the heaters and coolers rapidly downward to the starting point of a new upward pass. The

switch poles

75 and 76 are used to reverse the connections on the limit switch 53 so that the heating cycle takes place in accordance with the direction selected.

The switch 69 being closed, current flows through the jog switch to the single pole of the limit switch 53 which has closed the contact 72. Current will then flow to the pole 76 of the switch 64 through its associated down contact and thence to the pole 74 which is in contact with its corresponding down contact. This energizes one of the two

coils

77 and 78 of the slow motor 51, which is a reversing synchronous motor. This motor thereby turns in one direction. The current continues through the proportional timer 65 (assuming that the switch 79 is closed) and then back to the source of current.

When the carriage carrying the heaters and coolers reaches the lower limit of its predetermined path of travel, the carriage strikes the trip lever 55 on the con trol rod 54 and this throws the switch 56 so as to open the contact '72 and close the contact 80. This deenergizes the slow motor 51. The current then flows from the switch 60 through the jog switch 62 to the pole of the switch 53 which has then closed the contact 80. It then flows to the pole 75 of the switch 64 through its associated down contact and from there through the switch 63 to the field coil 81 of the fast motor 52, which is an induction motor, and then back to the source of current. When the carriage is moved rapidly by the fast motor back to the upper limit of its predetermined path, the switch 53 is reversed and the cycle is repeated.

It will be noted that, if a single heating pass is desired, all that is required is opening of the switch 63, since this breaks the circuit to the field coil of the motor 52. The carriage will stop as soon as the slow motor is deenergized by throwing the limit switch 53.

As stated, when the slow motor is deenergized, it is mechanically disconnected from the shaft by a solenoid operated clutch (the solenoid 82 only is shown in FIG- URE 2). FIGURE 6 shows that the solenoid is energized whenever the fast motor 52 is energized. Throwing the limit switch 53 at the end of a heating and cooling path, therefore, deenergizes the slow motor 51, energizes the fast motor 52, and, at the same time, actuates the clutch operated by the solenoid 82 so as to disengage the motor 51 from the shaft 44.

If it is desired to have the heating cycle occur during upward motion of the heaters and coolers, then the switch 64 is thrown so as to close the circuit through the four poles of this switch and their associated up contacts. As is apparent from the drawing, the motor 51 is reversed by having one or the other of the two

coils

77 or 78 energized in accordance with the position of the switch. That is, when the

poles

73 and 74 close the up contacts, the field coil 77 is energized, and, when the down contacts are closed, the coil 78 is energized. The direction of rotation of the motor 52 is controlled by two

shading coils

83 and 84, the direction being selected by shorting out one of the two coils for one direction and the other coil for the other direction. Referring to FIGURE 6, it will be seen that, when the up contact associated with the pole 73 is closed, then the shade coil 83 is shorted. When the down contact associated with the pole 73 is closed, then the coil 84 is shorted.

The proportional timer 65 is a timer in which a cam driven by a constant speed motor closes and opens the switch 79 for selected periods of time, the time intervals being determined by the position of the switch relative to the orbit of the rotating cam. The position of the switch is set by a knob 7921 on the panel 13 so that, by setting periods of time during which the switch 79 is opened and closed, the amount of time that the motor 51 is energized and, therefore, the amount of distance during which the carriage moves during any period of time can be regulated.

It will be noted from FIGURE 6 that the circuit for supplying current to the heaters parallels the circuit for the slow motor 51 and, therefore, current is supplied to the heaters only during slow passes of the heaters and coolers. The heating circuit includes the two step-down transformers 66 and 67 whereby a low voltage (in the order of 5 volts), high amperage current is supplied to the heaters.

As stated, the electrical circuit also includes a jog switch 62 whereby the heaters and coolers can be moved rapidly under the drive of the motor 52 to any position desired within the path of travel of the carriage. The jog switch 62 is manually operated and has three positions, a neutral position (shown in FIGURE 6), an up position, and a down position. The jog switch has four

poles

85, 86, 87, and 88. If the operator desires to raise the carriage, he throws the switch into the up position. This closes the contact 89 associated with the pole 85. The contact 90 associated with the pole 86 remains closed. The contact 91 is closed and the contact 92 remains closed. As is apparent from the figure, current will then flow through the field coil 81 and the motor 52. At the same time, the shading coil 83 will be shorted so that the motor 52 will operate to raise the carriage. If the operator desires to move the carriage downwardly, then he shifts the jog switch to the down position. This closes the contact 93 associated with the pole 85, the contact 94 associated with the pole 86, the contact 95 associated with the pole 87, and the contact 96 associated with the pole 88. Again, as is apparent from the figure, the field coil of the motor 52 is energized and the shading coil 84 is shorted out and the motor turns in a direction to lower the carriage.

It has been found that the efficiency of zone refining can be improved if the tube containing the sample is oscillated and, in FIGURES 7 and 8, we have shown mechanism for oscillating the tube 16 which holds the sample.

FIGURE 7 shows mechanism for oscillating the tube about its axis. The tube 16 is supported adjacent its upper end by a ring support 97 which is adjustably mounted on the support rod 15. A circular clamp 98 is fastened to the top of the tube 16 by thumb screws 99. The clamp 98 is carried by a shaft 100 which is mounted for rotation in the housing 9, the shaft 100 being held in the housing by a collar 101 threaded over the end of the shaft above the housing. A motor 102 mounted above the housing 9 and covered by a supplemental housing 9a turns a shaft 103 through reduction gearing 104. The shaft 103 carries a circular plate 105 at its lower end. A link 106 pivots on stub shafts 107 and 108 positioned adjacent the peripheries of the plate 105 and the clamp 98. Rotation of the plate 105 thereby causes the clamp 98 and, therefore, the tube 16 to oscillate about their central axes.

When the material being refined solidifies, it forms crystals which present an uneven surface at the surface of the molten zone in the material. Rotation of the tube and of the material in the tube moves the crystal faces across the surface of the molten zone and thereby agitates the liquid in the molten zone.

FIGURE 8 shows mechanism for oscillating the tube 16 longitudinally along its central axis. The mechanism comprises vibrating mechanism in a block 109 mounted on the support bar 15 below the level of the rod 20. The lower end of the rod 20 carries an armature 110 which is positioned directly above the poles of an electromagnet 111. The rod 20 is held in the block 109 by a rubber ring 112 and collar 113 which hold the rod 20 in such position that the armature 110 is spaced a slight distance away from the poles of the electromagnet 111. The rubber ring, however, will allow limited axial movement of the rod 20 against the resilient force of the ring which tends to restore the rod to its original position. The electromagnet is supplied with an alternating current which will draw the armature 110 towards the poles. When the value of the alternating current passes through zero, the rubber ring 112 will raise the rod 20 from the magnet and thereby an oscillating movement will be imparted to the rod 20 and thereby the tube 16.

From the foregoing, it is apparent that we have developed a compact instrument for carrying out zone refining of materials in a more accurate manner than has heretofore been possible. At the same time, the actual operation is simpler than has heretofore been possible. Our instrument provides for a very close control of the speed at which a molten zone is passed through a sample being refined. The size of the zone can be closely controlled by regulating the current supplied to the heaters and by adjusting the distances between the heaters and coolers.

The molen zone can be passed through the sample in either direction and the machine can be set so that only one pass is made through the sample or as many passes as desired are carried out automatically.

While we have described certain presently preferred embodiments of our invention, it is to be understood that it may be otherwise embodied within the scope of the appended claims.

We claim:

1. A zone refiner comprising a support for an elongated tube containing a sample to be refined, a heater for supplying heat locally to the sample within the tube,

tube forsupplying localized cooling to the sample, a carriage supporting the heater and cooler adjacent to the tube, and means for moving the carriage parallel to the tube 'Whereby localized heating and cooling are supplied to the sample along its length within the tube, the heater and cooler being adjustably mounted on the carriage whereby the extent of localized heating may be controlled.

, 2. A zone refiner comprising a support for an elongated tube containing a sample to be refined, a carriage movable parallel to the tube when it is positioned in the support, a plurality of heaters and coolers adjustably mounted on the carriage and positioned adjacent to the tube for supplying localized heating and cooling to the sample in the tube, the heaters and coolers being spaced alternately from each other and longitudinally of the tube, and means for moving the carriage parallel to the tube.

8 selecting in which direction said carriage may be driven by each of the two motors.

4. A zone refiner as described in claim 3 and including a reversing switch to supply current independently of said first two switches to said fast motor and drive it in either direction.

5. A zone refiner comprising a support for an elongated tube containing a sample to be refined, a heater for supplying heat locally to the sample within the tube, a cooler spaced from the heater longitudinally of the'tube for supplying localized cooling to the sample, a carriage supporting the heater and cooler adjacent to the tube, means for moving the carriage parallel to the tube whereby localized heating and cooling are supplied to the sample along its length within the tube, said means for moving the carriage comprising two motors operating at different speeds and an electrical circuit for selectively driving each motor and for changing the direction of each motor when said heaters and coolers reach each end of the 3. A zone refiner comprising a support for an elonsample in the tube.

gated tube containing a sample to be refined, a heater for supplying heat locally to the sample within the tube, a cooler spaced from the heater longitudinally of the tube for supplying localized cooling to the sample, a carriage supporting the heater and cooler adjacent to the tube, means for moving the carriage parallel to the tube whereby localized heating and cooling are supplied to the sample along its length within the tube, a slow speed reversible electric motor and a. high speed reversible electric motor for alternatelydn'ving said carriage moving means in either direction, a first switch actuated by movement of said carriage moving means for alternately supplying current to the two motors, and a second switch connected between said first switch and said motors for References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Keck: Review of Scient-lnst., vol. 25, #4, pages 331- 334, April 1954.

Bell Tel. Lab. Transistor Technology," vol. 1, September 1952, pages 31, 44, 52 and 54.

Claims

1. A ZONE REFINER COMPRISING A SUPPORT FOR AN ELONGATED TUBE CONTAINING A SAMPLE TO BE REFINED, A HEATER FOR SUPPLYING HEAT LOCALLY TO THE SAMPLE WITHIN THE TUBE, A COOLER SPACED FROM THE HEATER LONGITUDINALLY OF THE TUBE FOR SUPPLYING LOCALIZED COOLING TO THE SAMPLE, A CARRIAGE SUPPORTING THE HEATER AND COOLER ADJACENT TO THE TUBE, AND MEANS FOR MOVING THE CARRIAGE PARALLEL TO THE TUBE WHEREBY LOCALIZED HEATING AND COOLING ARE SUPPLIED TO THE SAMPLE ALONG ITS LENGTH WITHIN THE TUBE, THE HEATER AND COOLER BEING ADJUSTABLY MOUNTED ON THE CARRIAGE WHEREBY THE EXTENT OF LOCALIZED HEATING MAY BE CONTROLLED.