Colloid mill

The shear gap between a rotor and a stator in a colloid mill is adjusted by translating the stator with respect to the rotor, preferably by moving the stator along a helical path about the rotor, thereby moving the stator's surface closer to or further from the rotor's surface (and altering the shear gap therebetween). Helical slots are provided in the casing about the stator, with members extending from the stator through the slots, whereby the members can be grasped and rotated about the casing to move the stator. Channels allowing circulation of buffer fluid are provided about the stator and rotor to deter ingress of the fluid being processed into junctures between components of the colloid mill.

FIELD OF THE INVENTION

This document concerns an invention relating generally to equipment for processing fluids, and more specifically to colloid mills.

BACKGROUND OF THE INVENTION

Colloid mills are used in the food, pharmaceutical, cosmetic, paint, and other industries to reduce the particle sizes of matter in suspension, or of emulsified droplets, in a fluid. In a colloid mill, the fluid to be processed is fed through a shear gap between a high-speed rotor and a stator, with the shear imparted by the rotor serving to break the suspended matter or droplets into smaller sizes (with higher shear typically resulting in smaller particle/droplet sizes).

Control of the shear applied by a colloid mill—and thus the resulting particle/droplet size within the processed fluid—is typically important. For example, when processing a foodstuff (such as a salad dressing, mayonnaise, yogurt, etc.), appropriate particle/droplet size is typically needed to obtain a particular texture/mouthfeel, to deter settling/separation of components, etc. Shear is primarily determined by rotor speed and the size of the shear gap, but while many colloid mills allow adjustment of rotor speed, they do not readily allow adjustment of the shear gap without time-consuming disassembly (e.g., to replace or reposition one or both of the rotor and stator). Many colloid mills also require some amount of disassembly for complete cleaning. These factors generate unwanted downtime and labor costs.

SUMMARY OF THE INVENTION

The invention, which is defined by the claims set forth at the end of this document, is directed to a colloid mill which at least partially alleviates the aforementioned problems. A basic understanding of some of the features of preferred versions of the invention can be attained from a review of the following brief summary of the invention, with more details being provided elsewhere in this document. To assist in the reader's understanding, the following review makes reference to the accompanying drawings (which are briefly reviewed in the “Brief Description of the Drawings” section following this Summary section of this document).

The colloid mill allows rapid alteration of the rotor/stator gap, and thus the shear induced on fluid flowing between the rotor and stator, by moving the stator with respect to the rotor. Referring to the exemplary version of the colloid mill100shown in the accompanying drawings,FIGS.1and4-5show the mill100in its closed (minimum gap102) state, andFIGS.2and6-7show the mill100in its open (maximum gap102) state. The colloid mill100has a rotor104(FIGS.3,5, and7) with a tapered outer rotor surface106(here a frustoconical outer rotor surface), with the rotor104being driven by a rotor shaft108; a stator110with a tapered inner stator surface112wherein the rotor104is situated (the inner stator surface here having a frustoconical shape complementary to that of the outer rotor surface106); and a casing114situated about the stator110and rotor104. The casing114includes a fluid inlet116and a fluid outlet118(best seen inFIGS.1and2), and a fluid shear path extends from the fluid inlet116to the fluid outlet118to pass through the shear gap102between the outer rotor surface106and the inner stator surface112(as best seen inFIG.7). At least one of the inner stator surface112and the outer rotor surface106bears protrusions120extending therefrom (here, as best seen inFIG.3, ridges extending in planes coincident with the axis of rotation of the rotor104). Thus, fluid entering the fluid inlet116is sheared between the (rotating) rotor104and stator110as it flows toward the fluid outlet118.

As best seen by comparison ofFIGS.5and7, the stator110is movable within the casing114with respect to the rotor104, with such movement altering the shear gap102between the outer rotor surface106and the inner stator surface112: as the stator110translates from its open position inFIG.7toward its closed position ofFIG.5, with the inner stator surface112more fully receiving the rotor104therein, the tapered inner stator surface112approaches the tapered outer rotor surface106. The translation is preferably effected by providing a member122which extends from the stator110through a helical slot124(FIGS.1-2) defined in the casing114, whereby the member122can be grasped and rotated about the casing114through the slot124. This moves the stator110along a helical path within the casing114, with the stator110both rotating and translating about the rotor104(and with such translation altering the shear gap102). The member122preferably has a knob126threaded thereon, whereby rotating the knob126about the member122can fix the member122within the slot124(here by the knob126urging a sleeve128fit about the member122against the casing114), thereby fixing the stator110at a desired location to provide a desired shear gap102. This adjustment of the shear gap102can beneficially be performed at any time (e.g., during operation of the colloid mill100) with minimal effort: no disassembly of the colloid mill100is needed, and as the distance between the fluid inlet116and fluid outlet118remains unchanged during adjustment, an operator need not reconfigure any fittings/components connected to the inlet116and outlet118.

The colloid mill100also preferably includes features which enhance its sanitation and cleanability. Apart from allowing flushing by connecting the fluid inlet116and the fluid outlet118to respective supply and drain lines for cleaning solution (such as water with detergents/disinfectants), buffer solution may be circulated through the mill100to deter the fluid being sheared/processed from entering junctures between mill components (where, for example, a fluid foodstuff under processing might decompose and form a source of bacterial contamination). Buffer solution may be supplied to a buffer inlet130(FIG.1) to flow through annular seal channels132in a rotor seal134situated about the rotor shaft108between the rotor shaft108and the casing114(FIGS.3,5, and7), with the seal channels132being bounded by the (stationary) seal134and the (rotatable) rotor shaft108, and with the buffer fluid then exiting the seal channels132at a rotor buffer outlet136(FIGS.2and5). The buffer solution flowing through the seal channels132therefore deters the fluid under processing from collecting between the rotor104and the seal134(also carrying away any fluid that happens to reach the seal channels132), and additionally helps to cool the seal134during rotation of the rotor104therein. The buffer solution then flows from the rotor buffer outlet136through a first fluid bridge138(FIGS.2and5) to a stator buffer inlet140, which supplies the buffer solution to a first annular stator channel142A (best seen inFIG.5) in the casing114adjacent the first (inlet) side of the stator110. The stator channel142A is situated between (and bounded by) the casing114and the stator110, and is preferably bounded on opposing sides by seals144(e.g., O-rings) situated between the casing114and the stator110to help retain the buffer solution within the stator channel142A. The buffer solution then travels through a second fluid bridge146(FIGS.1and2) to a second annular stator channel142B (best seen inFIG.5) in the casing114adjacent the second (outlet) side of the stator110, and then to a buffer outlet148(FIGS.2and5). The buffer solution flowing through the stator channels142A and142B therefore deters the fluid under processing from collecting between the stator110and the casing114, and also carries away any fluid that happens to reach the stator channels142A and142B.

Further potential advantages, features, and objectives of the invention will be apparent from the remainder of this document in conjunction with the associated drawings.

DETAILED DESCRIPTION OF EXEMPLARY VERSIONS OF THE INVENTION

Expanding on the discussion above, the construction of the exemplary colloid mill100is best understood with reference toFIG.3. The casing114includes a bearing block114A, a fluid input section114B having the fluid inlet116thereon, a stator adjustment section114C which bears the member122for adjusting the stator110(and thus the shear gap102), and a cover114D which has the fluid outlet118thereon. The bearing block114A rotatably supports the rotor shaft108on roller bearings150(FIGS.5and7), with the rotor shaft108having an input end152allowing the rotor104to be rotatably coupled to an appropriate motor. The rotor shaft108is also supported by the seal134(as seen inFIGS.5and7), which is fit within the end of the fluid input section114B that is affixed to the bearing block114A (via fasteners154). The stator adjustment casing section114C is affixed to the fluid input casing section114B, with the stator110being closely fit within these sections so that it can rotate therein when the member122is manipulated. The casing cover114D then closes the casing114, and is attached to the stator adjustment casing section114C (and to the fluid input section114B) via fasteners156. The rotor104is situated within the casing114, and within the stator110, over the rotor shaft108and between the seal134and a rotor fastener158(see alsoFIGS.5and7).

Regarding the other components shown inFIG.3, one seal144(O-ring) assists in sealing the casing cover114D to the stator adjustment casing section114C (seeFIGS.5and7), and the rest are paired to rest on opposite sides of the annular stator channels142defined on the inner circumference of the stator adjustment casing section114C and the fluid input section114B (seeFIGS.5and7). The first fluid bridge138(shown assembled inFIGS.2and5) and second fluid bridge146(FIGS.1and2) are shown disassembled into their component elbow connections160and bridge tubes162, these bridge tubes162preferably being transparent to allow an operator to view buffer solution (typically water) therein. One alignment pin164, which fits into blind holes166in the adjacent ends of the fluid input section114B and the stator adjustment casing section114C to assist with their alignment during installation of the fasteners156, is also shown, with others not being shown for sake of clarity. The bearing block114A includes a lifting eyelet168allowing it to be more easily lifted and repositioned by lifting equipment, as well as lubricant fittings for lubricating the roller bearings therein, namely a lubricant inlet170, a lubricant drain172, and a sightglass174for monitoring lubricant level within the bearing block114A.

For greater ease in adjustment of the mill's shear gap102, two members122(handles) are provided to adjust the stator110, each being provided in a respective helical slot124on opposite sides of the stator adjustment casing section114C. As best seen inFIGS.1and2, these slots124may bear indicia along their lengths which indicate the size of the shear gap102when the members122are aligned with a given indicium. The members122can thus be rotated about the stator adjustment casing section114C to attain a desired shear gap102, and the knob126smay be tightened to urge the sleeve128sabout the members122against the stator adjustment casing section114C, thereby fixing the stator110in place (and fixing the shear gap102at the desired setting). While the colloid mill100solely uses the members122to rotationally and translatably affix the stator110within the casing114, additional or alternative arrangements could be used, e.g., one or more members122affixed to the casing114could extend inwardly to engage one or more helical slots124defined on the outer surface of the stator110.

The outer rotor surface106and inner stator surface112have frustoconical shapes, though other tapered shapes with complementary closely-fitting relationships (e.g., a dome-like outer rotor surface106and a concavely-curved inner stator surface112) are possible. While the shear-enhancing protrusions120on the outer rotor surface106and the inner stator surface112are depicted as ridges which extend coplanarly with the axis of rotation of the rotor104, other protrusions120(teeth, helices, etc.) could alternatively or additionally be used, and protrusions120need not be provided on both the rotor104and the stator110.

To operate the colloid mill100, an operator connects a supply of the fluid to be processed to the fluid inlet116, connects an appropriate fixture to the fluid outlet118to receive the processed fluid, and simply uses the members122to adjust the shear gap102as desired (either prior to or during rotor104operation/shearing). Buffer solution, typically warm water, is preferably fed through the mill100during operation (and during post-operation cleanout) via the buffer inlet130and buffer outlet148to deter incursion of the fluid being processed into any spaces between the seal134and the rotor104, and between the stator110and the casing114.

The version of the colloid mill100depicted in the drawings and described above is merely exemplary, and the invention is not intended to be limited to this version. Rather, the scope of rights to the invention is limited only by the claims set out below, and the invention encompasses all different versions that fall literally or equivalently within the scope of these claims. In these claims, no element therein should be interpreted as a “means-plus-function” element or a “step-plus-function” element pursuant to 35 U.S.C. § 112(f) unless the words “means for” or “step for” are explicitly used in the particular element in question.