US3851826A

US3851826A - Apparatus for treatment of solids for analysis

Info

Publication number: US3851826A
Application number: US00396925A
Authority: US
Inventors: I Perlman
Original assignee: Technicon Instruments Corp
Current assignee: REVGROUP PANTRY MIRROR CORP A DE CORP; Alfa Laval AB
Priority date: 1973-09-13
Filing date: 1973-09-13
Publication date: 1974-12-03
Anticipated expiration: 1991-12-03
Also published as: IT1020783B; SE410403B; CA993861A; JPS5748969B2; DE2442657A1; JPS5055959A; FR2243726A1; NL7410768A; GB1457677A; SE7411374L; AU474761B2; FR2243726B1; AU7319474A; CH590079A5; BE818681A

Abstract

A mixer to reduce solids having a constituent of interest therein for analysis, which reduction is of a physical nature and takes place in a carrier liquid. The mixer is similar to a homogenizer and includes a cutter element which rotates relatively to a second cutter element and is mounted to float toward and away from the second element. The first cutter element has at least one hydrofoil surface portion on the face thereof obverse to the face thereof which coacts with the second element. When the first cutter element is rotated at speed, the action of such hydrofoil surface on the carrier liquid is such as to urge the first cutter element toward the second cutter element to obtain the optimum cutting gap between the cutter elements.

Description

United States Patent [191 Perlman 1 Dec. 3, 1974 [75] I Inventor: 1. Lee Perlman, Pound Ridge, NY.

[73] Assignee: Technicon Instruments Corporation,

Tarrytown, NY.

[22] Filed: Sept. 13, 1973 [21] Appl. No.: 396,925

Primary ExaminerGranville Y. Custer, Jr. Attorney, Agent, or Firm-S. P. Tedesco; S. E. Rockwell [57] ABSTRACT A mixer to reduce solids having a constituent of interest therein for analysis, which reduction is of a physi cal nature and takes place in a carrier liquid. The mixer is similar to a homogenizer and includes a cutter element which rotates relatively to a second cutter element and is mounted to float toward and away from the second element. The first cutter element has at least one hydrofoil surface portion on the face thereof obverse to the face thereof which coacts with the second element. When the first cutter element is rotated at speed, the action of such hydrofoil surface on the carrier liquid is such as to urge the first cutter element toward the second cutter element to obtain the opti mum cutting gap between the cutter elements.

10 Claims, 7 Drawing Figures [52] US. Cl. 241/46.1l, 24l/l99.l2

[51] Int. Cl. B02c 18/10 [58] Field of Search 241/4611, 46.17, 86.2, 241/87.l, 88,199.12

[56] References Cited UNITED STATES PATENTS 2,963,281 12/1960 Reiffen 241/4611 X 3,223,485 12/1965 Ferrari et a1 23/253 R 3,666,187 5/1972 Norris 241/46.l7

PMEMEL DEB SHEET MP 2 APPARATUS FOR TREATMENT OF SOLIDS FOR ANALYSIS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a mixer similar to a homogenizer.

2. Prior Art Ferrari et al US. Pat. No. 3,223,485 issued Dec. 14, 1965 illustrates and describes apparatus for treatment of solids for analysis. Further, there is in the prior art similar apparatus to physically reduce solids such as tablets and fibrous material, for example, in a carrier liquid, which reduction is similar to that obtained in a homogenizer and which apparatus is an improvement of the mixer of the aforesaid Ferrari patent.

In the aforesaid mixer construction which followed the Ferrari mixer construction, there was provided a cutter element which rotated and was driven relatively to a second cutter element for coaction therewith. The first cutter element was fixed to a driving shaft which was floatingly mounted for movement of the first cutter element toward and away from the second cutter element. The driving shaft was spring biased in a direction to urge the first cutter element toward the second cutter element and thereby control the cutting gap.

Ideally a cutting gap between coacting shear ele-.

ments should be a fine setting, even during operation of such elements, to assure the best compromise between minimum gap and physical interference between the cutting elements. Such spring-biased gap closing as described above has the advantages of avoidance of close gap adjustment, ability to approach zero gap, some compensation for wear of the cutting faces, and avoids change of gap caused by thermal changes in the cutting elements.

The use of such spring-biased cutter element presented certain problems. The spring bias of the movable cutter element resulted in an undesirable degree'of loading of such cutter element upon its companion in starting up the mixer which increased the torque requirement of such biased cutter element. Moreover such spring use resulted in abnormal friction in such starting up operation between the cutter elements. Further, the use of spring biasing of the shaft on which the movable cutter element was fixed required a thrust bearing structure merely for load translation effects axially of the last-mentioned shaft. The present invention obviates these problems.

SUMMARY OF THE INVENTION One object of the invention is to provide an improved mixer similar to a homogenizer for breaking up various solids to minute size in a carrier liquid. Another object is to provide such a mixer which includes a cutter element which rotates relatively to a second cutter element and is mounted to float toward and away from the second element. The first cutter element has at least one hydrofoil surface portion on the face thereof obverse to the face thereof which coacts with the second element. When the first cutter element is rotated at speed, the action of such hydrofoil surface portion on the carrier liquid is such as to urge the first cutter element toward the second cutter element to obtain the minimum cutting gap between the cutter elements.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a median sectional view in elevation of a mixer embodying the invention;

FIG. 2 is a bottom view of the cutter elements taken on line 2-2 of FIG. 1;

FIG. 3 is a fragmentary view similar to FIG. 1 but illustrating in an exaggerated manner the gap between the cutter elements when the mixer is not in operation;

FIG. 4 is a view taken on line 44 of FIG. 3; and FIGS. 4a-4c illustrate details of the lower cutter ele ment of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 there is shown a box-like body, indicated generally at 10, having a lower part 12 and an upper part 14 which parts define therebetween a mixing chamber 16. The chamber 16 has an inlet 18 formed in the upper part of the body which is in communication with an inlet hole in a flange structure 20, which hole is indicated at 22 and is provided for loading the chamber 16. The lower part 12 of the chamber-forming body has an opening 24 through the bottom thereof which is normally closed by a plug 24a which is removed usually only for removal of the contents of the chamber 16 and the rinsing of the chamber. The flange structure 20, when the parts are assembled, is held down on the upper part 14 of the body as by tiebolts, one of which is indicated at 26. The upper part 14 of the body has a central boss 27 depending into the chamber 16. The boss 27 has a central upwardly extending opening therethrough and extending through the upper extremity of the upper body part 14, which opening receives the hollow stub shaft 28 of cutter element 30 integral with the stub shaft 28.

As shown in FIG; 1, on the upper end portion of the stub shaft 28 a sleeve 32 is fast therewith. The sleeve 32 has one or more slots therein, one being shown, into which one or more radially inward projections of a retaining ring 34 project, respectively, to fix the shaft 28 against angular movement with reference to the chamber-forming body 10 in a manner which will appear more fully hereinafter. The upper end of the sleeve 32 shown in FIG. 1 is externally threaded to receive thereon an internally threaded nut 36 which is threaded down thereon in a manner to draw the shaft 28 upwardly to the extent that the cutter element 30 abuts the boss 27 and the retaining ring 34 is locked against the upper surface of the upper body part 14.

The flange structure 20 has extending from the central upper part thereof shaft housing 38 in fixed relation to the flange structure 20. The shaft housing 38 is in axial alignment with the stub shaft 28 and receives a shaft 40 extending through the housing 38 and through the stub shaft 28. As shown in FIG. 1, the flange structure 20 near the junction of the shaft housing 38 has a transverse opening 42 therein which is also adjacent bearing retainer 44 at the lower end of shaft housing 38. Within the housing 38 around the shaft are bearing

members

46 and 48. The shaft 40 projects upwardly from the upper end of the housing 38 as shown and a retainer 50 encircles the shaft in fixed relation to the housing at the last-mentioned end of the housing. Fast on the upper end of the shaft 40 is a pulley 52 above the housing 38 and secured to the shaft 40, as by a bolt 54.

The shaft 40 is a driving shaft for the cutter element, indicated generally at 56, which is located below the cutter element in a manner to coact therewith. The

shaft is driven from the pulley 52 through any suitable driving belt not shown, and it is to be noted that the construction and arrangement is such that the cutter element 56, which may be integral with the lower portion of shaft 50, travels axially between the positions shown in FIGS. 1 and 3. In the last-mentioned position, the travel being exaggerated for purposes of illustration as previously indicated, the cutter element 56 is spaced from the cutter element 30. In practice the travel of the cutter element 56 with shaft 40 may be ap' proximately 0.002 inch. It will be appreciated, of course, that the pulley drive of the shaft 40 permits this degree of movement. Downward movement of the shaft 40 is limited by abutment of the pulley against the housing. If desired a thrust bearing may be interposed between the pulley 52 and the upper extremity of the housing 38.

Turning now to the details of the configurations of the

cutter elements

30 and 56 as illustrated, the cutter element 30 has planar upper and lower surfaces, and, as best shown in FIG. 2, defines a plurality of laterally extending lobes 58. As shown in the last-mentioned view, the lobes are four in number, and as shown in FIG. 1, the lobes have substantial depth from top to bottom. The lobes 58 project radially from the hub portion of the cutter element 30 and have rounded distal ends, as at 60. The junctions of the vertical surfaces of the lobes 58 with the flat undersurface of the cutter element 30 form knife edges one being indicated at 39 in FIG. 1. The substantial height of the lobes serves the function of baffles. lt will be obvious to those versed in the art that, while in the illustrated form the cutter element 30 is stationary, this element could be driven if desired.

The cutter element 56 has upper and lower

planar surfaces

62 and 64, respectively, which are horizontally arranged as is the lower surface of the cutter element 30. Projecting laterally from the axis of rotation at an obtuse angle to one another are projections 66 of the cutter element 56, shown in FIG. 4 which is a plan view of the cutter element 56, and cutter element 56 rotates in the direction of the arrow of that view. In the illustrated form the projections 66 are three in number. Each projection 66 is formed in part by a substantially planar vertically arranged surface 68 and a substantially planar vertically arranged surface portion 70, one such surface portion being shown in FIG. 4a. The distal end of each projection 66 is formed on a radius, as indicated at 72. At an angle to each such end surface 72, in the manner shown in the broken lines in FIG. 4 and in full line in the remaining views of FIG. 4, is an undercut 74 providing a hydrofoil surface portion sloping upwardly from the planar surface 64 to the vertically disposed surface portion 70 of each projection 66. The junction of the upper surface 62 of the cutter element with the surface 70 of each projection 66 forms a knife edge 76. The cutter element 30, together with the shaft 28, may be formed of metal or ceramic material, for example. If desired, the cutter element 56, together with the lower portion of the shaft 40, may be formed of ceramic material.

The operation of the mixer apparatus, described above, will be readily understood from the foregoing. The mixer may be incorporated as a part of an entirely automated analysis system. Before the first sample and the carrier liquid therefore is loaded into the chamber 16 the latter, while the bottom outlet 24 is open, is rinsed and then plugged as aforesaid. The charge in the chamber 16 may be of a plurality of tablets, for example, in the aforementioned carrier liquid. The inlet opening 22 may have associated therewith a splashguard not shown. At this time the

cutter elements

30 and 56 having the relationship shown in FIG. 3 in which the elements are disengaged. The drive of the shaft 40 is then initiated through the pulley 52, and it will be understood that the previously mentioned charge in the chamber 16 is sufficient for the cutter element 56 to be totally immersed therein and the cutter element 30 to be at least partially immersed in the charge. As the cutter element 56 on a shaft 40 attains speed, say for example and not by way of limitation 500 rpm, the hydrodynamic force of the partially liquid charge in the chamber 16 upon the hydrofoil surfaces 74 of the cutter element 56 causes the element 56 to lift upwardly with the shaft 40 until such lifting movement is stopped by abutment with the cutter element 30, the

cutter elements

30 and 56 then being in optimum shearing relation to one another and having the minimum gap therebetween, free of spring loading, for effective shearing action between the

elements

30 and 56 as the shaft 40 continues to be driven at or above the last-mentioned number of rpms.

The construction and arrangement avoid the necessity of gap setting of the cutter elements as they are self-gapping, with the ability to approach zero gap, while compensating for wear on the cutting faces and thermal changes in the cutter elements. When the mixer has been run a sufficient length of time to pulverize the tablets so that they may, in some instances, enter solution in the carrier liquid or form a suspension therein, the driving force on the shaft 40 is stopped. As the speed of the shaft 40 is reduced the cutter element 56 drops fron the engaged position of FIG. 1 to the disengaged position of FIG. 3. it will be understood that. prior to the discontinuance of the operation of the mixer as aforesaid, the mixture in the chamber, in addition to having the solids cut or pulverized or shredded by the

cutter elements

30 and 56, is heavily agitated and that during such agitation the mixture is forceably thrust against the baffles 58 of the cutter element 30 and repelled therefrom to enhance the mixing action. Upon discontinuance of the operation of the mixer as aforesaid, the opening 24 at the bottom of the chamber 16 is unplugged and the contents drained through the opening with at least a portion thereof passing to an alysis in a manner similar to that illustrated and described in the aforementioned Ferrari et a] US. Pat. No. 3,223,485 issued Dec. I4, 1965. The cycle is then repeated until all of the samples have been treated by the mixer in the aforementioned manner.

In addition to the aforementioned advantages of the mixing apparatus is the feature that, if the mixer is run with the chamber 16 unloaded, no such hydrodynamic force is exerted on the movable cutter element 56 such as to cause it to engage with the

cutter elements

30 and 56 and therefore wear between the cutter elements when run in a dry condition is avoided.

While only one form of the mixer has been illustrated and described, it will be apparent, especially to those versed in the art, that the mixer may take other forms and is susceptible of various changes in details without departing from the principles of the invention.

What is claimed is:

1. Apparatus for mixing solid sample material in a carrier liquid for analysis, comprising: a first cutter element, a second cutter element, said first cutter element being driven relatively to said second cutter element about a rotary axis for a shearing action between said cutter elements which are engageable with one another, and means mounting said first cutter element for floating movement toward and away from said second cutter element, each of said cutter elements having on one face thereof plural knife edges in array about said axis, said first cutter element having means thereon to shift said first cutter element to gap-closing relationship with said first element and maintain such relationship during operation of such apparatus for mixing and to move in a direction away from said second cutter element upon termination of such operation.

2. Apparatus as defined in claim 1, wherein: said means on said first cutter element comprises at least one hydrofoil surface portion which when said first cutter element rotates at speed receives a hydrodynamic force from the carrier liquid to effect shifting of the last-mentioned cutter element to gap-closing position with said second cutter element.

3. Apparatus as defined in claim 1, wherein: said first cutter element is provided with plural projections from said axis which are arranged at an obtuse angle to one another, each having one of said knife edges thereon.

4. Apparatus as defined in claim 1, wherein: said second cutter element is provided with a plurality of lobes which project radially from said axis in array therearound, said lobes having substantial height.

5. Apparatus as defined in claim 1, wherein: said gapclosing faces of said cutter elements are substantially flat.

6. Apparatus as defined in claim 2, wherein: said first cutter element has a plurality of lateral projections in array around said axis, each projection having on said obverse face a hydrofoil surface portion.

7. Apparatus as defined in claim 2, wherein: said hydrofoil surface portion is spaced from said knife edge.

8. Apparatus as defined in claim 3, wherein: each of said projections has a long side edge and a short side edge, and said knife edge on the projection being formed on the short edge.

9. Apparatus as defined in claim 4, wherein: the distal end of said lobes are rounded.

10. Apparatus as defined in claim 8, wherein: said means on said first cutter element comprises a hydrofoil surface portion which when said first cutter element rotates at speed receives a hydrodynamic force from the carrier liquid to effect shifting of the lastmentioned cutter element to engaged position with said being formed by an inclined surface which is spaced from said knife edge.

Claims

5. Apparatus as defined in claim 1, wherein: said gap-closing faces of said cutter elements are substantially flat.

10. Apparatus as defined in claim 8, wherein: said means on said first cutter element comprises a hydrofoil surface portion which when said first cutter element rotates at speed receives a hydrodynamic force from the carrier liquid to effect shifting of the last-mentioned cutter element to engaged position with said second cutter element, said hydrofoil surface portion being formed by an inclined surface which is spaced from said knife edge.