US3773423A

US3773423A - Automatic analyzer

Info

Publication number: US3773423A
Application number: US00282729A
Authority: US
Inventors: C Hach
Original assignee: Hach Chemical Co
Current assignee: Hach Co
Priority date: 1972-08-22
Filing date: 1972-08-22
Publication date: 1973-11-20
Anticipated expiration: 1990-11-20

Abstract

An automatic analyzer which combines a measured volume of a liquid sample with measured volumes of reagents in proper order, mixes and times the reacting liquids, and senses resulting liquid color by pouring the mixture through a colorimeter. The analyzer has only one major moving part - a driven center tube mounting measuring and feeding units, mixing units, and mixing and holding units, with the tube serving as a conduit between units and to the colorimeter. A measuring and feeding unit, upon rotation of the tube, dips a lifting passage into an underlying supply of fluid, lifts a quantity of the fluid by rotation of the passage, pours the liquid into an adjustable measuring pocket with the excess spilling back into the container, and finally pours the measured volume into the tube. The mixing unit receives liquid and spills it through a tortuous path upon rotation before returning the then mixed liquid to the tube. The mixing and holding unit spills liquid along a spiraling passage before returning it to the tube and thus holds the liquid for the number of tube revolutions equaling the coils in the spiral of the passage. The tube itself is slightly inclined so that liquid flows under gravity from unit to unit eventually to the colorimeter.

Description

United States Patent 11 1 Hach AUTOMATIC ANALYZER [75] Inventor: Clifford C. l-Iach, Ames, Iowa [73] Assignee: IIach Chemical Company, Ames,

Iowa

- 221 Filed: Aug .22, 1972 21 Appl. No.: 282,729

[52] US. Cl. 356/181, 23/253 R, 23/259, 73/244, 250/218, 259/89, 356/36, 356/196 [51] Int. Cl. G0lj 3/46, GOln 1/00, G02f 3/04 [58] Field of Search 356/36, 180, 181, 356/182, 246, 196, 197; 250/218; 259/89;

[56] References Cited UNITED STATES PATENTS 3,712,144 l/l973 Kuzel et a1 356/36 3,364,865 l/1968 Theuriaux 73/244 Primary Examiner-David Schonberg Assistant Examiner-V. P. McGraw Attorney-C. Frederick Leydig et al.

[57] ABSTRACT An automatic analyzer which combines a measured NOV. 20, 1973 volume of a liquid sample with measured volumes of reagents in proper order, mixes and times the reacting liquids, and senses resulting liquid color by pouring the mixture through a colorimeter. The analyzer has only one major moving part a driven center tube mounting measuring and feeding units, mixing units, and mixing and holding units, with the tube serving as a conduit between units and to the colorimeter. A measuring and feeding unit, upon rotation of the tube, dips a lifting passage into an underlying supply of fluid, lifts a quantity of the fluid by rotation of the passage, pours the liquid into an adjustable measuring pocket with the excess spilling back into the container, and finally pours the measured volume into the tube. The mixing unit receives liquid and spills it through a tortuous path upon rotation before retuming the then mixed liquid to the tube. The mixing and holding unit spills liquid along a spiraling passage before returning it to the tube and thus holds the liquid for the number of tube revolutions equaling the coils in the spiral of the passage. The tube itself is slightly inclined so that liquid flows under gravity from unit to unit eventually to the colorimeter.

11 Claims, 14 Drawing Figures AUTOMATIC ANALYZER This invention relates generally to automatic chemical analyzers and more particularly concerns a continuous analyzer for colorimetrically monitoring a given characteristic of a flowing liquid sample over long periods of time.

Chemical analyzers which react to a color change in the sample under investigation upon the addition of one or more reagents normally depend for accuracy upon bringing together closely controlled amounts of reagent and sample. Such accurate metering has, in the past, been achieved with precision pumps or with capillary passages. However, pumps for this purpose are usually intricate and expensive, and capillary metering is subject to clogging problems and is dependent upon viscosity which, in turn, is a function of temperature which must therefore be controlled. Despite such problems, however, continuous automatic testing, particularly of water intended for any one of a variety of uses, has become an increasingly sought-after objective. Continuous monitoring of a flowing water supply for acidity, chlorine or fluoride content, hardness, and/or iron or other metallic concentrations, to name just a few characteristics, is of value in water treatment plants, power stations and other industrial and agricultural situations.

The general aim of the invention is to provide an improved analyzer that is economical to manufacture and operate, requiring virtually no maintenance, and which functions accurately and reliably without viscosity, i.e. temperature, control.

It is also an object of this invention to provide an analyzer as characterized above which is rugged and damage-resistant in that measuring, mixing, and aging or timing functions are carried out by a solid, single assembly, so that even relatively complex tests are automatically and repeatedly run with what is virtually a single moving part.

Another object is to provide an analyzer of the above described type which is made up of components that can be assembled in groups, arrangements and proportions to perform a wide variety of tests varying in number and quantity of reagents employed, and in timing or aging of the reaction steps.

A further object is to provide an analyzer as referred to above which, for accuracy and reliability, mechanically measures and mixes, and mechanically times or ages under the control of an ordinary synchronous motor.

Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in

y rhich:

FIG. 4 is a fragmentary section taken approximately along the line 4-4 in FIG. 3;

FIG. 5 is a fragmentary section corresponding to FIG. 4 but showing the unit in an alternate operating position;

FIG. 6 is a section taken approximately along the line 6-6 in FIG. 4;

FIG. 7 is an enlarged fragmentary longitudinal section of another one of the units shown in FIG. 1;

FIG. 8 is a section taken approximately along the line 88 in FIG. 7;

FIG. 9 is a fragmentary section taken approximately along the line 99 in FIG. 8; and

FIG. 10 is an enlarged fragmentary section taken along the line l010 in FIG. 1.

While the invention will be described in connection with a preferred embodiment, it will be understood that I do not intend to limit the invention to that embodiment. On the contrary, I intend to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

Turning to the drawing, there is shown an analyzer 10 embodying the invention and including a number of sub-components arranged to test water introduced through a line 11 at a rate determined by the setting of a valve 12. To illustrate the construction and operation of the invention, the analyzer 10 is set up to test for silica in the water sample using the heteropoly blue method in which a water sample is taken; ammonium molybdate in an amount equaling a 50th part of the water volume is added, mixed and held for 5 minutes; oxalic acid in an amount equaling a 50th part of the water sample volume is next added and mixed; and finally an amino acid solution in an amount equaling a 50th part of the water sample volume is added, mixed and held for another 5 minutes. A blue color developed in the solution is indicative of the presence of silica in the water sample. The analyzer 10 performs this test automatically and repeatedly on water flowing in from the line 11. It will be apparent, once the analyzer is understood, that other arrangements of the analyzer components can be assembled to perform a wide variety of other test procedures involving measuring, mixing, holding and color checking of thesample and test reagents.

The components of the analyzer 10 include a center tube 15 rotatably driven by a synchronous motor 16, a sample measuring and feeding unit 17, a pair of reagent measuring, mixing and holding units 18 and 19, a reagent measuring and mixing unit 20, and a colorimeter 21 of the flow-through type. The units 17-20 are all fixed on the tube 15 for simultaneous rotation with the tube, and the reagent units 18-20 are enclosed in tanks 22, 23 and 24 containing, respectivelyfammonium molybdate, oxalic acid and a solution of amino acid. The sample unit 17 also rotates on the tube 15 into a container 25 which receives water for testing from the line 11 through the valve 12. All of the components of the analyzer 10 are supported in a suitable frame 26, schematically indicated, which includes a discharge line 27 for draining the water and reagent solution from the analyzer following testing.

Considering first the measuring and feeding of the water sample, the unit 17 includes a body 30 having a liquid receiving core fitted tightly around the tube 15 which defines the axis about which the body 30 rotates.

The body 30 defines a measuring pocket 31 adjacent the core and having an open top leading to an opening 32 in the tube 15. The pocket 31 also has a spill wall side whose edge 33 defines the top of the pocket 31 and thus the upper level of liquid in the pocket when the pocket is disposed beneath the axis of the tube 15 (see FIG. 2a).

The body 30 also includes a cup and tube defining a lifting passage 34 leading from the top of the pocket 31 to a point well spaced from the axis of the tube 15, with the passage 34 having a bottom surface generally facing the axis of the tube so that rotation of the body on the tube with the tube axis generally parallel to the water in the container 25 will sequentially cause the bottom of the passage 34 to dip into the liquid, raise a quantity of liquid from the supply and pour the raised liquid quantity into the pocket 31 the sequence illustrated in FIGS. 2 and 2a. The passage 34, particularly the cup portion thereof, is proportioned to raise and pour into the pocket 31 a volume of liquid significantly greater than that retained by the pocket spill wall side. Preferably, the passage 34 is also sufficiently large in diameter that the liquid flows smoothly without bridging across the passage. The edge 33 of the spill wall is rounded and made hydrophilic so that liquid spills smoothly thereover with a minimum capillary effect from surface tension, and the edge 33 is also curved about the axis of the tube 15 so as to maintain a substantially fixed wall height through a range of rotation of the body 30 about that axis. In the illustrated embodiment, the hydrophilic property is imparted to the spill wall edge 33 by forming the body of polyvinyl chloride and slightly roughening that edge, as by sanding or chemical etchmg.

As a result of the spill wall configuration, a precise volume of liquid is retained in the pocket 31, the excess spilling over the spill wall edge 33, with the top of the retained liquid being almost exactly at the spill wall edge when the pocket is beneath the tube 15 (see FIG. 211). To adjust this precisely measured volume, a member 35 is adjustably mounted, in this case by a threaded connection, for movement into and out of the pocket 31 so as to permit selective variation of the pocket volume. Once having been measured, the liquid content of the pocket 31 is poured into the tube 15 through the opening 32 upon continuing rotation of the tube (see FIG. 2b). In keeping with the analysis performed by the analyzer 10, the unit 17 measures and feeds into the tube ml. of water sample upon each tube revolution.

The measuring portions of the units 18-20 are structurally virtually alike and conceptually similar to the structure and operation of the unit 17. Taking the unit 18 as representative, it includes a body 40 in the form of a disk having a liquid receiving core tightly fitted on the tube which defines the axis about which the body 40 rotates (see also FIG. 3). The body 40 defines a measuring pocket 41 adjacent the core and having an open top leading to an opening 42 in the tube 15 (see also FIG. 4). The pocket 41 also has a spill wall side whose edge 43 defines the top of the pocket and thus the upper level of liquid in the pocket when the pocket is beneath the axis of the tube 15 (see FIG. 3a).

The body 40 is formed with a spiral groove in its outer face defining a lifting passage 44 leading from the top of the pocket 41 to a point well spaced from the axis of the tube 15, with the passage 44 having a bottom surface generally facing the tube axis so that rotation of the body on the tube with the tube axis generally par- I side 43. Preferably, the groove forming the passage is sufficiently large that the liquid flows smoothly without bridging across. The edge 43 of the spill wall is rounded and made hydrophilic so that liquid spills smoothly thereover with a rninumum capillary effect, and the edge 43 is also curved about the axis of the tube 15 to maintain a substantially fixed wall height through a range of body rotation about that axis. As was the case in the unit 17, the hydrophilic property can preferably be imparted to the spill wall edge 43 by forming the body 40 of PVC and slightly roughening the edge 43 as by sanding or chemical etching.

As a result of the spill wall configuration, a precise volume of liquid is retained in the pocket 41 upon rotation of the tube 15, the excess falling over the spill wall with the top of the liquid retained being almost exactly at the spill edge 43 when the pocket is beneath the tube 15 (see FIG. 3a). To adjust this measured volume, a member 45 is adjustably mounted, in this case by a threaded connection 46, in the body 40 for movement into or out of the pocket 41 so as to permit selective variation of the pocket volume. Once measured, the fluid reagent in the pocket 41 is poured into the tube 15 through the opening 42 upon continuing rotation of the tube. Again, following through with the analysis performed by the analyzer 10, the unit 18 measures and feeds into the tube 0.1 ml. of ammonium molybdate upon each tube revolution.

The center tube 15 is slightly inclined (see FIG. 1) so that there is gravity flow of liquid from the high end, on which the sample unit 17 is fixed, to the low end, under which the colorimeter 21 is mounted. The ends of the tube are sealed by plugs 47 and 48, the plug 48 carrying a pin 49 rotatably seated in the frame 26 so as to define a bearing and the plug 47 being formed to slide over an irregularly shaped output shaft 51 forming part of the motor 16. The tube 15 is thus drivingly connected to the motor, although it can be easily removed from the analyzer frame for cleaning or other servicing.

The

units

17 and 18 are angularly phased on the tube 15 so that the lower, or downstream, unit 18 pours its reagent into the tube 15 just ahead of the upstream water sample being received into the tube so that the sample, in effect, washes all of the reagent along. To insure that liquid in the center tube 15 will not spill back into the unit 18, an introduction tube 53,fitted into the center tube 15, opens from the tube opening 42 to the opposite side of the center tube 15. Thus, with the pocket 41 above the axis of the tube 15, liquid spills through the opening 42 and through the introduction tube 53 directly into the path of the onflowing water sample at the bottom of the center tube. Further rotation of the center tube places the introduction tube opening above the then bottom of the center tube (see FIG. 3a) so that, in the event that there is some residual liquid in the tube, that liquid will not flow back into the pocket 41 to disturb the accuracy of the next reagent measurement.

It will be recalled that the unit 18 in the illustrated analyzer is a measuring, mixing and holding unit intended to mix 0.] ml. of ammonium molybdate with 5.0 ml. of water and to hold that mixture for 5 minutes. The mixing and holding portion of the unit 18 comprises a body 55 in the form of a disk having a liquid receiving core fitted tightly on the center tube and a spiraling passage 56 leading from the periphery of the body 55 to an opening 57 in the tube 15. Preferably, the passage 56 is milled into one face of the disk body 55 and is closed by the

bodies

40, 55 being sealed to one another. The liquid solution is introduced to the outer end of the spiraling passage 56 through a generally radial passage 58 formed in the body 40 which connects a pair of openings 59 and 61 and is sealed by a plug 62 adjacent the opening 61. A wall 63 within the tube 15 provides a fluid-tight block to fluid flow down the tube so that liquid introduced by the

units

17 and 18 is forced into the opening 59 and through the passage 58 to the opening 61 and the spiraling passage 56 (see FIGS. 3b and 5).

In the illustrated analyzer, the synchronous motor 16 rotates the tube 15, and thus the units 17-20, at the rate of one revolution per minute. Thus, the passage 56 is spiraled five times about the axis of the tube 15 with the result that five revolutions, and five minutes, are required to have fluid flow along the passage 56 from the opening 61 to the opening 57 which leads back into the center tube 15 on the downstream side of the blocking wall 63.

To avoid having the liquid in the passage 56 bridge that passage and possibly develop a blocking bubble, the passage 56 is formed, with an increasing cross section as the radius of the spiral increases (see FIG. 4).

The measuring and mixing unit includes measuring structure virtually identical to that found in the unit 18 and therefore it will be identified with the same reference numerals havingthe distinguishing suffix a added. Thus, the measuring portion of the unit 20 includes a body 40a defining a pocket 41a whose volume is adjusted by a member 45a and whose upper edge is defined by a spill wall edge 43a. The pocket is filled by a lifting passage 44a, and the pocket pours that reagent,

upon continued rotation of the tube 15, into an opening 42a in the tube and through an introduction tube 53a. The

units

18 and 20 are angularly phased on the tube 15 so that, in the illustrated analyzer 10, 0.1 ml. of oxalic acid from the container 23 is poured intothe center tube through the introduction tube 53a just as the 5.1 ml. of solution is poured from the body 55 so that the further reagent is washed along.

The mixing portion of the unit 20 includes a body 65 in the form of a disk having a liquid receiving core fitted tightly onthe center tube 15, a pair of

openings

66 and 67 angularly spaced about the axis of the tube 15 which serve as inlet and outlet openings, and a tortuous serpentine path 68 defined by spoke-like recesses connecting the

openings

66, 67. The path 68 is preferably formed by milling the recesses into the face of the body 65 with the passage being closed by the bodies 65 and 40a being sealed to one another. A passage 69 is formed in the body 40a adjacent a wall 63a in the tube 15 (see FIG. 7) which leads to and defines the opening 66. As will be apparent, solution poured through the opening 66 will, upon rotation of the unit 20, spill from one spoke of the recess into the next along the serpentine passage 68 so as to thoroughly mix the solution.

The unit 19, a measuring, mixing and holding unit, is identical to the unit 18 and will not therefore be described in greater detail. In the illustrated analyzer 10, the unit 19 functions to add 0.1 ml. of amino acid solution from the container 24 to the previously mixed solution already traveling down the tube 15. Unit 19 is angularly phased with respect to the unit 20 so that the reagent is poured into the tube 15 from the unit 19 just as the solution flows down from the upstream unit20. Following the 5-minute holding and mixing cycle developed by the unit 19, the solution is poured from that unit back into the tube 15, from which it flows through a collar 70 (see FIG. 10) into the colorimeter 21. Appropriate filters and light sensors in the colorimeter respond to the development of the test color, blue in this case, so as to indicate the presence or absence of silica in the water sample under test.

It will be appreciated that the analyzer 10 is a continuously cycling apparatus, and that a number of samples will be simultaneously in the process of passing through the various units 17-20. Once all of the units are, in effect, full then successive checks will be made every revolution of the tube 15, i.e., every minute. Upon startup, it is desirable to allow several samples to pass completely through the analyzer so that proportioning of the reagents can become stabilized. It will be noted that, for example, the unit 20 will deposit about six measured amounts of the reagent associated with that unit in the tube 15 before the first water sample reaches that unit so that, until a few samples have passed through theentire analyzer, the possibility of inaccurate proportioning in the solution exists.

The tanks 22-24 are preferably formed in two pieces, having spacious bottom portions 71 to contain a longlasting quantity of reagent, and tops 72 which enclose the respective units as well as the tank bottoms so as to avoid contamination. Filler holes and plugs 73 permit convenient replenishing of the reagent contents, and the openings through which the center tube 15 passes are preferably closed by annular flap valves 74.

Those skilled in this art will appreciate that the analyzer 10 can be manufactured quite economically, particularly when it is compared with those analyzers requiring expensive pumps and valving. The analyzer 10 also operates accurately and reliably while requiring virtually no maintenance. The analyzer is quite temperature stable since there are no critical flow rates which might be affected by a change in the viscosity of the liquids being handled.

It can also be seen that the components of the analyzer 10 are quite rugged and, indeed, there is virtually but a single moving part which can be quite solidly made. This rugged, simple construction has been achieved despite the relatively sophisticated nature of the analysis being carried out.

It has already been pointed out that a wide variety of tests can be set up by arranging the components of the analyzer 10 so as to produce a desired sequence of measuring, mixing and holding virtually any number of reagents with the sample under investigation.

I claim as my invention:

1. A liquid measuring and feeding'unit for automatic analyzers comprising a body having a liquid receiving core at an axis about which the body rotates, said body defining a measuring pocket adjacent said core and having an open top open to the core, said pocket also having a spill wall side for defining the top of the pocket and thus the upper level of liquid in the pocket when the pocket is beneath said axis, said body also defining a lifting passage leading from the top of said pocket to a point well spaced from said axis, said passage including a bottom surface generally facing said axis so that rotation of the body thereon with the axis generally parallel to a supply of liquid will sequentially cause the surface to dip into the liquid, raise a quantity of liquid from said supply and pour the raised liquid quantity into said pocket, and said passage being proportioned to raise and pour into said pocket a volume of liquid greater than that retained by said spill wall side.

2. The unit of claim 1 in which the edge of said spill wall adjacent said core is rounded and hydrophilic so that liquid spills smoothly thereover with minimum capillary effect, and said edge is curved about said axis to maintain a substantially fixed wall height through a range of body rotation about said axis.

3. The unit of claim 1 including, in combination, a member adjustably mounted in said body for movement into or out of said pocket so as to selectively vary the volume of the pocket.

4. The unit of claim 1 in which said passage has a cross section sufficiently large so as not to be bridged by liquid being conveyed to said pocket.

5. A liquid holding and mixing unit for automatic analyzers comprising a body having a liquid receiving core and an axis about which the body rotates, said body defining a spiraling passage leading from the body periphery to an opening at said core, and said body also having a liquid introduction opening for allowing liquid to flow into the peripheral end of said passage whereby the liquid will flow into said core after a predetermined number of body revolutions about said axis.

6. The combination of claim 5 in which said spiraling passage is formed with an increasing cross section as the radius of the spiral decreases so as to avoid having the liquid volume bridge the passage.

7. A liquid mixing unit for automatic analyzers comprising a body having a liquid receiving core at an axis about which the body rotates, said body having a pair of openings angularly spaced about said axis for serving as inlet and outlet openings, and said body also having a tortuous serpentine path connecting said pair of openings so that, upon rotation of said body, liquid introduced through one opening is mixing by spilling along said passage before exiting through the other openlng.

8. An analyzer comprising, in combination, a frame, a center tube mounted for rotation in said frame and being disposed at an angle with respect to the horizontal so as to have a high end and a low end, a colorimeter in said frame having a liquid receiving passage beneath the lower end of said tube, a plurality of liquid containers in said frame spaced beneath said tube, a plurality of liquid measuring and feeding units mounted on said tube for rotation into respective ones of said containers upon rotation of the tube, and means in said frame for rotating said tube so that said units lift liquid from said containers, spill back all but a measured volume and pour that volume into said tube, said tube having an opening above said colorimeter so that the total of said measured liquid volumes flows into the colorimeter.

9. The combination of claim 8 including an introduction tube fitted into said center tube and opening from one of said units to the opposite side of the center tube on which the unit is mounted so that liquid in the center tube will not spill back into said one unit.

10. The combination of claim 8 including a mixing unit mounted on said center tube at a lower tube portion than where a pair of said measuring and feeding units are mounted, said mixing unit being open to the tube for receiving liquid and having a path for spilling the liquid through a tortuous path upon rotation of the center tube before allowing the liquid to flow to said colorimeter.

11. The combination of claim 8 including a mixing and holding unit mounted on said center tube at a lower tube portion than where a pair of said measuring and feeding units are mounted, said mixing and holding unit being open to the tube for receiving liquid and having a path for spilling the liquid through a spiraling path upon rotation of the center tube through a predetermined number of revolutions before allowing the liquid to flow to said colorimeter.

Claims

1. A liquid measuring and feeding unit for automatic analyzers comprising a body having a liquid receiving core at an axis about which the body rotates, said body defining a measuring pocket adjacent said core and having an open top open to the core, said pocket also having a spill wall side for defining the top of the pocket and thus the upper level of liquid in the pocket when the pocket is beneath said axis, said body also defining a lifting passage leading from the top of said pocket to a point well spaced from said axis, said passage including a bottom surface generally facing said axis so that rotation of the body thereon with the axis generally parallel to a supply of liquid will sequentially cause the surface to dip into the liquid, raise a quantity of liquid from said supply and pour the raised liquid quantity into said pocket, and said passage being proportioned to raise and pour into said pocket a volume of liquid greater than that retained by said spill wall side.

7. A liquid mixing unit for automatic analyzers comprising a body having a liquid receiving core at an axis about which the body rotates, said body having a pair of openings angularly spaced about said axis for serving as inlet and outlet openings, and said body also having a tortuous serpentine path connecting said pair of openings so that, upon rotation of said body, liquid introduced through one opening is mixing by spilling along said passage before exiting through the other opening.