US3333828A

US3333828A - Homogenizer

Info

Publication number: US3333828A
Application number: US441087A
Authority: US
Inventors: Gotthard E Boehme
Original assignee: Norton Co
Current assignee: Saint Gobain Abrasives Inc
Priority date: 1965-03-19
Filing date: 1965-03-19
Publication date: 1967-08-01
Anticipated expiration: 1984-08-01
Also published as: FR1467683A; GB1148822A; DE1300426B; SE312538B

Description

G. E. BOEHME HOMOGENIZER Aug. l, 1967 Filed March 19, 1965 ENTOR E HM E ATTORNEY United States Patent O 3,333,828 HGMOGENIZER Gotthard E. Boehme, Cropseyville, N.Y., assignor to Norton Company, Troy, N.Y., a corporation of Massachusetts Filed Mar. 19, 1965, Ser. No. 441,087 6 Claims. (Cl. 259-9) The invention relates to a method of and apparatus for homogenizing various types of mixtures and more particularly to a shear type apparatus which is elective in homogenizing very lumpy, high viscosity fluid mixtures of materials such as rubber-based pressure-sensitive adhesive compositions, paint formulations, natural and synthetic latices and the like.

Heretofore processes for reducing the lumpiness of adhesive and other coating materials and of obtaining proper particle size and dispersion involved many different and repetitious steps before the material was acceptable for use as a coating material. It would be desirable to eliminate these repetitions time-consuming procedures and to produce a superior, smooth, lump-free, homogeneous creamy mixture which can be easily spread to form a uniformV coating of good adhering qualities. Such result has heretofore been unobtainable despite the presence of many varied and costly types of apparatus on the market.

It is, therefore, the object of the present invention to provide a simple, low cost, shear type homogenizer.

Another object is to provide an apparatus which can homogenize a great variety of flowable materials.

A further object is to provide an apparatus which can be quickly and easily adapted to the material to be homogenized.

An additional object is the provision of an improved method for homogenizing uid mixes.

Another object is to provide an apparatus which can produce a superior lump-free homogeneous mixture during a single pass therethrough.

Additional objects, if not specilically set forth herein will be readily apparent to one skilled in the art from the following detailed description of the invention.

lIn the drawings:

FIGURE l is a longitudinal cross-sectional view in elevation through a homogenizer built in accordance with the present invention.

FIGURE 2 is a transverse cross-sectional view in elevation taken on line 2-2 of FIGURE 1.

Generally, the present invention is directed to providing a method and apparatus for subjecting a Huid composition -to be homogenized to a repeated shearing action with small increments of the composition being acted upon individually, said method and apparatus being especially adapted for in-line continuous homogenizing. The iiuid mix is subdivided into many small portions and each of these portions is subjected to a high shear. The portions are then reunited and the process repeated until the mix is homogenized to the desired degree. More specifically, the present invention comprises the provision of a plurality of rotatable, cylindrical, multiple tooth, tluted cutters mounted within an elongated, stationary tube. This tube is perforated with many holes and has spaced collars about its entire periphery forming a plurality of separate chambers within a bore inside a fixed housing, said `chambers intercommunicating with each other through said perforations in said tube and in the central portion of said tube communicating directly with each other.

In operation, the fluid composition to be homogenized (hereinafter referred to as the mix) is progressively forced under constant pressure and volume into the various chambers and through the many holes in the tube to form a plurality of small separate streams. As these streams come through the holes in the tubethey are immediately sheared into small portions or increments by rotating cutters within the tube opposite the various chambers and iinally the mix moves out an exit pipe or conduit in a thoroughly homogenized condition.

Referring now to the drawings, the homogenizing apparatus 10 comprises an elongated stationary housing 12 with an outer wall 14, an inner wall 16 and

end Walls

18 and 20 separated by a chamber 22. The housing 12 has a central bore 24 into which is closely fitted a stationary concentric perforated tube assembly 30. The tube assembly 30 consists of a perforated thin walled tube or cylinder 32 with numerous spaced holes 34 extending through its wall. The size and number of the perforations or holes in the tube may be varied to suit the application, and also the size and number of holes may be progressively increased or decreased from one end of the tube to the other. For example, the preferred size and spacing are 3&2" holes on 3/16" staggered centers. However, many variations can be used as desired.

Fixed, as for example by spot welding, to the exterior surface of the perforated tube 32 are a plurality of spaced, axially aligned collars or

spacers

36, 36a, 36b, 36e and 36d of identical or similar construction closely fitting the bore 24. The collars 36-36d form with the bore 24 of member 12 a plurality of separate chambers 38, 38a, 3819 and 38e extending entirely about the respective exterior portions of the perforated tube 32. A plurality of holes or passages 40 in the spacer or collar 36b interconnect the chamber 38a and 38h whereby the mix can flow directly from the one chamber to the other. Chambers 38 and 38a and the chambers 3812 and 38C are made intercommunicating only by the holes 34 in the respective adjacent wall portions of the tube 32.

Rotatably mounted within, and in close shearing engagement with, the interior surface of the tube 32 is a series of identical left-hand spiral type multi-toothed cutters 42 mounted axially on and keyed to a central rotatable shaft 44 journaled in bearings 46 and 4S mounted in the end caps S0 and 52 fixed to the housing 12. A baille 54 si-tuated between the two central cutters and keyed to shaft 44 interrupts the flow of the mix along the flutes of the cutters 42 and forces the mix to exit from the tube 32 into chamber 38a via holes 34. The cutters 42 may be of Various types such as standard lluted high speed steel milling machine cutters with straight or spiral multiple cutting teeth. The cutting teeth may also be of the readily available adjustable insert type which can be extended radially for resharpening purposes and for maintaining the proper shearing action between the interior surface of the tube 32 and the cutters 42.

In some applications, for example where the mix consists of volatile materials, it may be necessary to prevent the temperature of the apparatus from reaching a critical flash point or to prevent altering certain desirable properties of the mix which otherwise would be affected by overheating. Therefore, means are provided, when it is necessary to maintain the desired temperature of the apparatus to control the temperature. These means comprise pipes or conductors 56 and 58 interconnected with chambers 60 and 62 about the portions supporting the bearings 46 and 48 in the

end caps

50 and 52. The chambers 60 and 62 are interconnected with the chamber 22,

formed by outer and'inner

walls

14 and 16 within the housing 12, by a plurality of aligned passages or holes 64 and 66 extending from both the

end caps

50 and 52 through the respective end wall portions 1 8 and 20 of member 12. To prevent rotation of the tube assembly 30, pins 63 in the end cap 52 extend into recesses 69 in the collar 36d. Gaskets 70 and 72 are provided for preventing any leakage of materials from the joints between the respective end caps 5t) and 52 and the stationary housing 12.

Other seals are lprovided such as an O ring 74 compressed against the end of the bearing 46 and, hence, against the rotatable shaft 44 by an adjustable nut 76 screwed onto the end of end cap S0, and sealing rings 78 of coupling member 80 fixed to the shaft 44 and rotatable within grooves in the face of nut 76.

The described means permits a coolant or heat exchange medium such as water, controlled in any well-known manner, to be circulated through the apparatus to provide the desired operating temperature.

The homogenizing apparatus is rotatably driven by any suitable commercially available drive means 82 such as a hydraulic, pneumatic, or electric motor having a coupling member 84 iixed to its output shaft 83 in driving engagement with the coupling member 80. However, in order to homogenize a greater variety of mixes with a single apparatus, an adjustable variable speed drive means of suicient horsepower is preferred. Different mixes require different rates of speed and power in relation to the feed rate of the mix through the apparatus in order to achieve the optimum result in terms of uniformity of mixing in a given period of time.

In order to convey the various mixes to and from the apparatus, an inlet pipe 90 and outlet pipe 92 are provided. The pipe 90 directs the mix, which is preferably under pressure, into chamber 38, while pipe 92 permits the exhaust of the mix from chamber 38C. A drain plug 94 is provided for removing any foreign matter which may accumulate in chamber 38.

Means for forcing the various mixes through the apparatus are well known in the art and are commercially available. For example, sutiable means such as constant pressure and volumetric delivery pumps (not shown) with means for varying the pressure and volume of mix delivered to the homogenizer are advantageous in providing the proper feed rates for a great variety of mixes.

In operating the homogenizer of the present invention, drive means 82 is started in motion and, as shown in the drawing, this causes rotation of the shafts 83 and 44 and the cutters 42 (which in this illustration have left-hand spiral teeth) in the direction of the arrow.

It will be noted that there is a spiral recess or liute between adjacent teeth along which the mix can flow. In fact, the angled face of each tooth of the cutters 42 acts as a pump which is especially helpful in moving high viscosity mixes along the utes and into the adjoining chambers. However, the pressure exerted on the mix is usually suicient to cause the mix to flow regardless of the design of the cutting teeth.

The mix first enters chamber 38 surrounding the exterior of tube 32 and is then forced through all of holes 34 in that portion of the tube 32. As the mix protrudes from the holes beyond the interior surface of the tube 32, the cutting teeth of cutters 42, which must be in close shearing engagement with the interior surface of the tube 32, immediately shear through the mix and drop it into the flutes or recesses between the cutting teeth. The mix then flows axially i-nto the llutes of the adjacent cutter at the end of Which is the baffle 64 preventing further axial movement of the mix. Consequently, the mix is forced from within the tube 32 where again the cutting teeth shear through the mix as it moves through the holes 34 into the chamber 38a. From chamber 38a the mix moves continuously through the multiple passage 40 into chamber 38h. Collar 36C prevents direct flow of the mix into chamber 38u` and the mix is forced through the holes 34 about that portion of the tube 32 encompassed by chamber 38h and is again sheared by the teeth of another cutter 42. The mix is then directed axially along the flutes of adjacent cutters 42 until it meets up with end cap 52. At this point, the mix is forced to again move from within the tube 32 through holes 34 where it again receives a shearing treatment and proceeds through such holes 34 into chamber 38C and thence out through outlet pipe 92. If necessary during operation, any suitable temperature control medium can be circulated through the apparatus as described above.

It can be seen that the mix is subjected to repeated shearings in very small increments as it flows through the homogenizer and that there is no possible way of any lumpy material escaping such shearing action. In addition, the number of shearings can be increased or decreased by varying the volume of the mix, rate flow of the mix, pressure on the mix, the number and size of holes per unit area of the tube 32, the rate of rotation of the cutters, the number of cutting teeth on each of the cutters, and/ or the number of chambers in the apparatus which is illustrated constitute four in number but which could easily be increased, or lone or more of the homogenizers could be connected in series if desired.

As stated above, the present invention is especially useful in homogenizing rubber-based adhesive coating mixtures which tend to become lumpy very easily. For example, an adhesive mix formulated from parts natural rubber, 50 parts zinc oxide, 85 parts tackier resins and 14.3 parts of plasticizer, antioxidants, etc. was solvated with a toluene-tolusol solvent to a viscosity of 15,000 c.p.s. at 80 F. This gave a very lumpy, owable mix consisting of about 40% solids with the remainder being solvent. Before being homogenized by apparatus embodying the present invention, the temperature of the mix was 80 F., and the plasticity was 2.58 millimeters as measured on a Williams Plastometer. One hundred and fty gallons of the adhesive mix was then forced through W32" diameter holes on 3/16" staggered centers in a 3.00" inside diameter stainless steel tube 12" long with a pressure of 80 p.s.i. at a volume of 5 gallons per minute, -while the four milling cutters, each having 16 teeth and being 3 in length rotated at 2,000 revolutions perminute. There were four chambers in this unit as illustrated in the drawings and the number of perforations provided approximately 22% open area for each chamber. Each chamber was 2.375" in length and -the inner bore of t-he stationary housing was 4" in diameter. The collars or spacer rings were 1/2 thick and with an outside diameter of 4" to lit the inner bore with a sliding t. The baille plate was thick stainless steel with a 3 outside diameter.

The resulting homogenized mixture drawn olf at F. was of excellent quality, absolutely free of lumps and of a smooth creamy consistency which produced an excellent coating mass.l Fluid mixes of varying viscositiesy have been satisfactorily homogenized according to this invention ranging from 5 to 500,000 centipoises at 80 F. with a percent solids of from 20 to 42%.

There has been provided by the invention an effective, quick, simple, low cost, method -and apparatus for homogenizing a variety of mixtures including mixtures which heretofore were either non-homogenizable or extremely difficult to homogenize. Since many variations may lbe,

made encompassing the above invention, it is to be understood that all matters hereinbefore set forth or shown inv the accompanying drawings are to be interpreted as illustrative and not in a limiting sense.

I claim: 1. Homogenizing apparatus comprising in combination:

a stationary housing member having an inlet and outlet;

a bore extending through said housing and communi-v forming entrance and exit chambers external to.

said stator and communicating with said interior zones only through the perforations of said stator, the exit chamber of said first zone communicating directly with the entrance chamber of said second zone;

cutting means mounted within said bore being so disposed and arranged as to have shearing contact with the entire inner surface of said perforated stator and forming therewith a plurality of fluid-conducting channels; and

means to pass a uid mix to be homogenized successively into said rst and second zones in shearing Contact with said cutting means as such fluid mix enters and exits from each of said zones.

2. An apparatus as in claim 1 wherein said perforated stator means is a thin-walled perforated tube.

3. An apparatus as in claim 1 wherein said cutting means are mounted on a shaft disposed within said bore and wherein said perforated stator means is subdivided by an imperforate bale member axed to said shaft and positioned within said stator means completely separating the interior of said stator means into the two separate zones.

4. An apparatus as in claim 1 wherein said means surrounding said stator within said bore comprises a plurality of spaced, axially aligned collars forming with said bore and said stator a plurality of longitudinally spaced annular chambers communicating with said zones inside said stator solely through the perforations of said stator and wherein one only of said annular chambers is directly in communication with a second of said annular chambers to provide indirect communication from said irst zone through said perforations of said stator to said one chamber, to said second chamber, and through said perforations of said stator from said second chamber to said second zone.

5. An apparatus as in claim 1 wherein said cutting means comprises a rotatable, imperforate cutter so arranged as to conduct a fluid mix in contact therewith in a plurality of channels from the inlet end of said housing towards said outlet end.

6. A method of homogenizing a fluid mix which comprises subdividing a fluid mix into a plurality of small streams; passing said plurality of small streams into a rst zone; shearing each of said small streams into multiple small portions as it passes into said first zone; reuniting each sheared and subdivided stream within said rst zone to form a plurality of mixes; passing said plurality of mixes out of said zone in the opposite direction to their entry into said zone; shearing said mixes as each exits from said irst zone to form multiple small portions; passing these small portions from said rst zone in the form of a plurality of small streams; reuniting said streams outside said zone to reform said mix; redividing said reformed mix into a plurality of small streams; passing said plurality of small streams into a second zone; shearing each of said small streams into multiple small portions as it passes into said second zone; reuniting each sheared and subdivided stream wit-hin said second zone to form a plurality of mixes; passing said plurality of mixes out of said second zone in the opposite direction to their entry into said zone; shearing said mixes as each exits from said second z-one to form multiple small portions; passing these small portions from said second zone in the form of a plurality of small streams; reuniting said streams outside of said second zone to reform a mix; and repeating said steps until said mix is homogeneous.

References Cited UNITED STATES PATENTS 2,169,339 8/1939 Ditto 259-9 2,688,470 9/ 1954 Marco 259-9 X 2,882,149 4/1959 Willems 259-96 X 3,195,867 7/1965 Mould 259-9 3,257,175 6/1966 Brooks et al. 259-97 X WALTER A. SCHEEL, Primary Examiner.

I. M. BELL, Assistant Examiner.

Claims

1. HOMOGENIZING APPARATUS COMPRISING IN COMBINATION: A STATIONARY HOUSING MEMBER HAVING AN INLET AND OUTLET; A BORE EXTENDING THROUGH SAID HOUSING AND COMMUNICATING WITH SAID INLET AND OUTLET; PERFORATED STATOR MEANS INTERNALLY SUBDIVIDED INTO A FIRST AND SECOND SEPARATE ZONE MOUNTED WITHIN AND EXTENDING THE FULL LENGTH OF THE BORE; MEANS SURROUNDING SAID STATOR WITHIN SAID BORE AND FORMING ENTRANCE AND EXIT CHAMBERS EXTERNAL TO SAID STATOR AND COMMUNICATING WITH SAID INTERIOR ZONES ONLY THROUGH THE PERFORATIONS OF SAID STATOR, THE EXIT CHAMBER OF SAID FIRST ZONE COMMUNICATING DIRECTLY WITH THE ENTRANCE CHAMBER OF SAID SECOND ZONE; CUTTING MEANS MOUNTED WITHIN SAID BORE BEING SO DISPOSED AND ARRANGED AS TO HAVING SHEARING CONTACT WITH THE ENTIRE INNER SURFACE OF SAID PERFORATED STATOR AND FORMING THEREWITH A PLURALITY OF FLUID-CONDUCTING CHANNELS; AND MEANS TO PASS A FLUID MIX TO BE HOMOGENIZED SUCCESSIVELY INTO SAID FIRST AND SECOND ZONES IN SHEARING CONTACT WITH SAID CUTTING MEANS AS SUCH FLUID MIX ENTERS AND EXITS FROM EACH OF SAID ZONES.