CA2204321A1 - Horizontal mixer apparatus and method with improved shaft end seal structure - Google Patents

, ~TTORI~I~Y DOCKET NO: LFO/Oi!A
HORIZONTAL MIXER APPARATUS AN~ IYIETHOD WITH
IMPROVED Sl IAFT END SEAL STRUCTURE
Field of the Invention This in~ention relates generally to apparatus and method for industrial mixing and processing and particularly to horizontally arranged indus~rial mixers having horizontally disposed mixing shafts extending through the mixing chamber.
Backqround of the Invention Processing of a large variety of consumer and industrial products, such as food, plastic, pharmaceutical and chemical products, usually involves one or more mixing steps for mixing cornponent materials of the products. Such mixing sTeps are oftentin~es accompanied by simuitaneous drying of the rnaterial 1~ being mixed and granulation or chopping of the material. The techniques of mixing a product with materials in a dry, powdered or granular forrn, is generally referred to as solids mixing For accomplishing such solids mixing, large-~apacily industrial mixers are utilized which are able to handle very large loads of malerial for rnore efficient and cost-effective mixing. One type of mixer design, which is able to effectively mix large loads of malerial, is referred ~o as a horizontal mixer because its elongaled mixing chamber is disposed generally horizon~all~ vvjth respect to the ground surface on which it rests. More specifically, horizon~al mixers generally comprise a mixing chamber, an elonga~ed, horizontal mixing shaft ~hich rotates, and a plurality of mixing tools v~Jhich depend generally perpendicularly from the horizontal shaft to rolate around the inside of the chamber. The mixing tools are configured and dimensioned as required for ~he mixing process to follow the cylindrical inside walls of the chamber for proper mixing of all of the material in the chamber when the shaft rola~es.
Some such mixing chambers are cylindrically shaped, while others are trough-shaped such as mixers which are commonly referred to in Ihe art as double-arm mixers or ribbon mixers.
The horizontal mixin~ shafl extends out of the chamber at both ends through appropriate openings in ~he chamber end wa,lls or head walls. At one end of the sha~t, referred to as the drive end, Ihe shafl is operably coupled to a drive molor for rotating the shafl. A~ ~he drive end, the shaft is coupled throl~gh a bearing slruclure located belween the driv~ molor and the chamber. The bearing structure provides support of the shaft drive end and also ensures smooth rotation A separate seal s~ructure is then located further in along the length of th~ shaf~ and interfaces with the opening in the end wall through which the mixing shaf~
extends. The drive end seai structure, which ~nay be a dynamic seal or mechanical seal, seals the shaft o~ening and generally prevents the passage or leakage of material into and out of the mixing chamber. The seal structures used in horizontal mixers are important lo ensure the integrity and purity of the material being mixed and are a~so necessary for preventing leaks and protecting the health of ~orkers in the area of the mixers~ As may be appreciated, leakage between the horizontal mixing chamber and the atmosphere during mixing is a significant concern.
For example, edible products such as pharmaceuticals and foods rnust not be con~aminated with foreign rnaterials which may leak into the mixing chamber al the shaft openings. As may be appreciated, grease or oil associa~ed with the drive motor and/or th,e shaft bearings must be kepl out of the mixing chamber.
Furlhermore, it is also equally important to contain the mixed ma~erial in the charnber and to prevent it from migrat;ng and leaking outside through the shafl openings. This is particulariy so if the material being mixed is a harmful chemical which cannot be directly contacted by Ihe skin or if the mixed ma~erial produces a harm~ul vapor which rnay be released through Ihe shaft openings.
Oftentimes, carcinogenic ma~erials are mixed in horizontal mixers, and it is particularly important to prevent the escape of the maT~rial or the vapors associaled therewith.
Still further, i~ may be necessary to maintain a pressure differential within the horizonlal mixing chamber for proper rnixing~ For example, some mixing procedures rnay require eleva~ed pressures within the chamber which tend to force mixed material out through the seals Other procedures require that a vacuum be drawn in the chamber, thus tending to draw con~arninants into the chamber through the seals.
As a result, conven~ional horizonlal mixers utili2e complicated bearing structures and separate seal struct~res which may include elaborate and complicated dynamic seals with braided packing elements that surround the rotating shaft or expensive ~echanical seals. The packing elements of the dynamic seals are constantly worn by Ihe rota~ion and movement of the shaft and thus are prone ~o leakage. Sorne such seals are coupled to an air line for preventing migration or Ieakage of the mixed rnalerial out of the chamber or the leakage of contaminants into the chamber.
Conventional mechanical seals have highly polished faces which spin against each other under pressure. Such mechanical seals are often expensive due to the precise machining and polishing .
necessa~y for their operation and are also subject to vvear and 1 0 leaka~e The problem of leakage al the shafl ends of a horizontal mixer is further exacerbated by the requirement of a seal at the stub end or non-driven end of the shaft. The slub end generally utilizes a separate bearing structure located out on the end of the shaf~ spaced trorn the end wall of the chamber. A
dynamic or mechanical seal, similar lo the seal at the drive end, is coupled IO the end wall inwardly on the shaft from The separate bearing structure. The stub end d~namic seal is prone to both rolational and transla~ional wear and leakage rather ~han jllst the rotational wear experienced at the drive end as discussed below.

Therefore, c-lrre~tly available horizontal mixers using expensive and elaborate combinations of intricate bearings and d)~narnic or rnechanical seal structures at the stub end of the shaft have numerous drawbacks. First, ~he requirement of having another separate bearing structure and another separate sealing structure which ~ust be separately fabricated and installed at the stub end increases Ihe overall cost of the mixer. Furthermore, the complicaled and involved dynamic seal designs or the expensive rnechanical seals currently used at the stub end of the horizontal mixers also increase the cost of manufacturing a mixer.
Additionally, as mentioned above, the existing stub end seal structures used ~ith horizontal mixers are prone to leakage, and thus, require maintenance in the form of replacing the worn packing elemenrs Ot other rnechanical sealing el~ments to prevent leaks. During such maintenance, whether scheduled or unscheduled, ~he mixer cannot operale, thus redulcing the efficiency of the mixing process and reducing the cosr-effectiveness of the mixer.
Bearing failure from teakage may also ~e a problem Tlle bearings used with conventional horizonlal mixers are intricately designed and have balls, rollers or other moving components which are lubricated with free lubricanls, such as grease or lubricating oil. When the seals leak, the mixed material may migrate lo the bearing and be trapped in the various cavities containing the balls, rollers and other cornponents and thus contaminant the lubricants. As a result, the ~earing may wear prematurely and be damaged, or ~he bearing may even lock up and hinder Ihe rotation of the shaft. Additionally, the mixed material may be chemically reaclive and may corrode the bearing Leakage at the stub end sealing structure is particularly a problem with exis~ing horizontal mixers because once ~he mixed material passes out of the chamber, i~ is exposed to ~he atmosphere. That is, there is generally no additional struclure adjacent the failed seal structure lo further prevem leakage. The bearing is spaced away from the stub end sealing structure and away from the end of Ihe chamber and thus does not provide any sealing properties. furthermore, the existence of the separate bearing prevents additional sealing slrlJctures from being utilized.
As a result, the operation and the integrity of the stub end sealing struc~ure is a predominant concern when uslng horizontal mixers.
As mentioned, some mixing material may be carcinogenic, and thus leaks may expose workers proximate to the mixers to carcinogens~
toxic gases or other dangerous chemieats The stub end seal structure is particularly prone IO
failure and leakage because of its position on the shaft. I~Jlore specifically, the stub end of the shaft not only rotates, but also moves in a longitudinal direction or in the direction of the longitudinal, horizontal axis of the shaft as the shaft expands and contracts in length d~le to the temperature changes associaled with the metal shaft. Since, the drive end of the shaft is somewhat fixed due to the drive motor and other associated components, the longitudinal translation of the shaft caused by expansion and conuaction of the shaft occurs primarily at the stub end. The translational movement of the shaft is due to ils constant exposure to the variations in lemperature caused by the he~ting and cooling of the chamber and Ihe hea~ generated by the mixing process.
Furthermore, the shaft itself ma~ be actually heated or cooled such as by introducing steam, water or oil into a cavity in the shaft Still further, the end walls or end plates of the mixing chamber will move in and out longitudinally with respecl to the shaft due to temperatur~ variations of the chamber. Therefore, Ihe sea1 structure and the packing elements at the stub end a~e exposed not only to rotational ~ear bu~ also ~o Iranslational wear, ~hus making the slub end seal structure parlicularly prone lo ~ailure and leakage.
Shaft deflection is also a concern associated with currenlly availa~le horizontal mixers. ~he rotating shafts of horizontal mixers are designed lo handle a certain amount of stress and to only deflect a predetermined amoun~ due lo the sag in the shaft between i~s supporled ends With stress and deflection as a Iimiting criteria, the shafts are designed and sized in diameter to achieve the acceptable defleclion For example, a deflection of 1/16 of an inch may be accep~able in one mtxer design, and thus The diameter of the shaft u/ill have to be sized accordingly. ~s will be appreciated, con~lention horizon~al mixers ~rhich support the shaft ends at spaced apart bearings will require relatiYely large diarneter shafts thus increasing the costs of the mixer. A larger diameter shaf~ will also require larger bearing and sealing cornponents, thus fur~her increasing Ihe cosrs of the mixer.
Accordingly, there is a need for a structure for both sealing and providing rota~ional support of the mixing shaft of a rnixer. There is particularly a need for a structure for sealing, supporting and rotating ~he shaft stub end in a horizontal mixer.

It is an objective of the presenl invention to address the drawbacks of the prior art and tO provide a mixer ~vhich is less expensive tO fabricate and requires less maintenance than currently available rnixers.
It is another objective to prevent leakage o~ mixed materials from the mixing chamber to tlle atmosphere and to prevent the leakage of outs;de contaminants into the mixing chamber.
It is anolher objective of ~he present invention to rotationally seal the ends of the mixing shaft of a hori~ontal mixer.
It is particularly an objective to provide an impro~ed rotational seal systern for the stub end of the mixing shaft.
It is anolher objective of the invention to reduce the maintenance required for Ihe sealing and bearing arrangements in a horizontal mixer and particularly the maintenance at the stub end of the mixer shaf~ To that end, ir is an objective to reduce the number of moving bearing parts which may become contaminated and subsequently fail.
It is still another ob3ective to reduce the cost and complexity of the sealing and bearing arrangement in a horizontal mixer at the sl~Tb end of the rnixing shaft.

- It is stiil another objective of the invention to utilize a small diameter shaft to decrease the cost of the mixer.
It is another objective of the invention to reduce the affect of lateral and rotational wear on the stub end sealin~
structure to reduce the seal failure associated with such wear and reduce the required maintenance for the sealing strucltJre.
lt is still another objective of the invention to provide proper rotationaT support and sealing of the mixing shaft stub end to prevent any migralion or leakage of foreign contaminants in~o the mixer and also ~o prevent the migration or leaka~e of the rnixed matcrials out of the mixer.
Summarv of the Invention The above-referenced objectives and other objectives are achieved by the hori~ontal mixer of the presem invention which provides an improved sealing and bearing structure for Ihe s~ub end of the rotating ~ixing shaft and improves the operation of the shaft and the sealed integrity of the mixing chamber. The invention reduces the necessary maintenance on the mixer and pravides an inexpensi~e yet durable stub end seal which is liquid and vapor tight and which prevents leakage inlo and out of the mixing chamber , To that end, the horizontal ITixer of Ihe present invention comprises a generally elongated chamber which is horizontally disposed and has an inside space con~igured for receiving material to be n~ixed An elongated rotatable mixing shaft extends longitudinally though the chamber space and has opposing ends which extend through openings in the end walls or head walls of the chamber The shaft is preferably coaxially mounted ~vith the chamber so that i~ rotates in the cen~er of the ins de space A
drive end of the shaft is operably coupled to a drive motor through an appropriale coupling, and the drive end is rotatably supported by a bearing structure At the respective end wall opening, a separate seal structure provides a dynamic seal belween the end wall of tlle chamber and the dri~e end of the rotating shaft to prevent ma~erial from migra~ing into or out of the chamber along the shaft through the drive end ~all opening The drive end bearing struc~ure is constructed to handle a substantial portion of the shaft load which is translated to the drive end Appropriate nlixing tools are a~ached generally perpendicular to the axis of the shaft to sweep around the inside chamber space and provide mixing within the chamber . : CA 02204321 1997-05-02 In accordan~e vvith the principals of the present in~rention, a stub end of the rotatable shaft extends through the other end ~all opening opposite the drive end of the shaft. The shaft stl~b end inciudes a bearing portion, and in a preferred embodiment of the invenrion, a hardened, wear-resislant steel sleeve is coupled to the stub end at the bearing portion A sleeve bearing is posilioned proximate the end wall and operably engages the bearing portion and sleeve of the stub end of the shaft. The sleeve bearing is posilioned proximate ~he end wall opening and is operable for rolalably supporting and sealing rhe shaft stub end close to ~he end wall. A bearing housing coupled ~o the end wall supports the sleeve bearing and maintains it in proper engagernent with ~he shaft stub end. A retaining ring is mounted within a hol~sing groove proximale the outside end of the bearing to confine 1~ the bearing, while a sho~lder of the housing at Ihe inside end of the bearing f~rther confines the bearin~. In that way, the invention is not particula~l~ susce~tible to the different expansion characteristics between the housing and bearing when hea~ is generated during the rotation of the shaft, and Ihe bearing is maintained in the proper position The sleeve bearing is preferably formed of a low-friction composite rnaterial for providin~ smooth rolation of the shaft stub end. furthermore the sleeve bearin~ is dimensioned in length to provide a proper amount of contact with Ihe stub end sleeve for efficient rotation and for rhe necessary support required by the stub end.
The horizontal mixer of the invention further comprises a sealing shroud coupled proximate the sleeve bearing and operable for covering an outer portion of the shaft stub end. The sealing shroud is preferably coupled ~o the bearing housing at an interface.
A stalic shroud seal is coupled between the bearing housing and shroud at the interface and ll~ereby the static shroud seal is maintained out of direct contact with the rotatable sha~t in accordance with the principles of the invention. The sealing shroud and the static shroud seal effectively and operably isolate the shaft stub such that any leakage Ihrough the sleeve bearing and stub end between the chamber space and atmosphere is ~3enerally preven~ed. Since Ihe static shroud seal and shroud are not affected by the rotation or longitudinal movemen~ of the shafl the seal integrity of the stub end is maintained The unique seal and bearing system of the invention reduces maintenance and provides ' CA 02204321 1997-05-02 proper containment of the mixed material and any v~pors associated therewith. Furthermore, Ihe shroud is preferably sized to pro~lide room for Ihe shaft lo longitudinally expand and contract during mixing.
The unique combination of the sleeve bearin~ and static seal strucrure and shroud of the present invention a~e relatively inexpensive and durable and reduce Ihe labor and material COSIS associated wi~h sealing and suppor~ing the stub end of the rnixing shaft. The seal achieved by Ihe invention is more durable ~han prior art dynamic seals and thus reduces leakage between the chamber space and atmosphere The stub end seal, which generally receives the mos~ wear in a horizontal mixer, is out of direct contact with the rolaling shaft and thus is not subje~t IO the imense wear presented by the rotating shafl. Furthermore, necessary mainTenance and the resulling shutdown of the mixing process required for such maintenance is also reduced.
The sleeve bearing struclure of the invention eliminates various moving bearing parts and components to conventionally used with mixers, such as ball bearings and roller bearings. Therefore, bearing failure is reduced and the inventive mixer requires less mainlenance.

~ CA 02204321 1997-05-02 .

The unique rotational supporT and sealing of the shaft stub end within the end wall opening provides support of the shaft closer to the chamber and thus reduces the diameter of the shaft necessary for achieving the desired deflectlon Accordingly, the resulting costs of manufacturing and sealing and supporting Ihe shaft are reduced.
A fur~her benefi~ of the present inven~ion over Ihe existing art is the elimination of a separate bearing slructure positioned and spaced out on the end of the shafl. Therefore, the s~ub end of the shaft is generally not confined in the iongitudinal direc~ion and the shaft is free to expand and contract in length without damaging the bearing and seal structure and wilhout putting any unnecessary stress on the shaft. Furthermore, the sealing capacity of the invention is not susceptible IO lateral uvear caused by such expansion and contraction because the static shro~ld seal is isolated from the rotating shaft.
The static shroud seal and shroud provide a iiquid tigh~
and vapor ~ight seal around the shaft stub end. The shroud preferabiy includes inie~ and outlet ports for introducing a fluid, such as vvaler or a suilable liquid, or pressurized ni~rogen or some other sui~able gas, around the shaft stub end. For example, ~ CA 02204321 1997-05-02 pressu~ized nitrogen might be utilized to purge product fronl the bearing and thereby exlend Ihe life of the bearing. Any vapors or materials leaking throl~gh the sleeve bearing will be maintained by the shroud and static seal, which are not affected by the rotation of the shaft or the wear on the sleeve bearing.
To further extend bearing life, one embodiment of the invention comprises a dynamic seal s~ructure which surrounds the stub end of the sha~t and engages the sleeve proximate an inside end of the sleeve bearing. The dynamic seal is operable for sealing l O the sleeve bearing and ~he end wall of the chamber proximate Ihe inside of the chamber during rotation of the shaft to prevenl leakage IO and through the sleeve bearing. The dynarnic seal of the invention is preferabiy a lip seal comprising a wear-resistant and chemical-resistant contact portion, e.g., Teflon, which engages the shaft sleeve and is held in contact therewith by a more rigid metallic porlion. An operable spring may be provided for further biasing the vvear-resistant con~act portion agains~ the smooth surface of the slee~e. The dynamic seal prevenls accelera~ed wear of the sleeve bearing by keeping mixed material from migrating between the sleeve bearing and housing or stub en~ sleeve.

In one embodiment of the inven~ion, the bearing housing is coupled lo a head plate, which, in turn, is coupled to the chamber end wall or head wall. for enhancin~ the seal integrity at the stub end wall opening, a static head seal suuclure, such as a rubber 0-ring, is coupled at the interface between the bearing - housing and Ihe head plate to provide a seal a~ the intertace.
To furlher seal the shaft stub end and prevent leakage a static sleeve seal str~lcture is utilized at the inside end of the shaft sleeve between the sleeve and the bearing portion of the shaft for prevenring any n~igration of materials out of the chamber through the shaft and sleeve interface.
An alternative ennbodiment of the invention cornprises a bearing housing mounted directly to ~he end wall. By mounling, the bearing housing direclly to the chamber end wall the additional head plate is eltminated. The inlerface between the end wall and mounting coilar is sealed by a static seal structure in accordance wilh the principles of the invention.
The structure of the present invention simultaneously provides a sealing and supporting structure for the stub end of the horlzontal mixing shaf~ of the horizontal mixer w~ich is inexpensive, durable and lo~v maintenance. The hor;zontal mixer is properly sealed to prevent leakage between the chamber and the atmosphere. Furlhermore, the unique construction of the invention reduces shaft diameter and th~Js reduces the cost of the mixer.
The stub end is also vapor sealed and harmful vapor leakage is th-ls S generally eliminated.
The above and other objects and advantages of the p~esent invention shall be made apparen~ from the accornpanying d~awings and the description thereof.
Brief DescriPtion of the Drawinq The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with a general description of the inven~ion given above, and tlle detailed description of the embodiments given below, serve to explain the principles of the 1 5 invention.
Fig. 1 is a front ~iew of a horizontal mixer constructed in accordance with the principles of the present invent;on;
Fig, 2 is a perspecti~/e view, parlially cut-away, of the sha~t slub end of the horizontal mixer illustraled in Fig. 1;

- 1g-.

Fi~. 3 is a cross-sec~ional view along lines 3-3 of Fi~.

2 illustrating the mixing shaft stub end in accordance with the principles of the presenl invention;
Fig. 3A is an enlarged cross-sect;onal view of the dynamic seal strucrure of the invention shown in Fig. 3;
Fig. 4 is a cross-sectional ~iew of an alternative embodlment of the invention sho~ving ~he mixing shaft stub end;
Fig. 4A is an enlarged cross-sectionai view of an alternative embodiment of ~he dynamic seal structure of the invention shown in Fig. 4.
Detailed Description of Specific Ernbodiments fig. I illustra~es a horizontal mixer 10 conslructed in accordance with the principles of the present ;nvention. The embodiment of the mixer 10 illustrated in Fig. 1 comprises a generally cylindrical and elongated mixing chambet 12 which is horizontally disposed and configured to receive Iherein material which is to be mixed, such as powered food malerial, pharmaceutical material or plastic material, for exarnple The cylindrical chamber 12 has a generally cylindrically~shaped side wall and opposing end walls or head walls 14a, 1 4b which close the ends of the chamber to contain the m;xed material. The chamber define~ an inside mixing space 15 for mixing the material.
Although a cylindrically-shaped chamber is illustrated, other horizon~al mixer shapes, such a trough-shaped mixers commonly referred to as ribbon mixers or double-arm mixers might also be ulilized in accordance with tl~e principles of the inven~ion. Other shapes of horizon~al mixers mighl also be utilized, Mixer 10 f~rther includes one or more charge ports 16 and one or more disc~harge ports 18 utilized for charging the chamber with materials to be rnixed and discharging the mixed material from chamber 12 after i~ has ~een properly mixed, The horizontal mixer 10 of the invention may atso include a ventilation port 20 or other appropriate struct~re for venrilating any fumes or vapors generated durin~ the mixing process and also for facilitaling charge an~ discharge of product. Furthermore, other apparatuses, 1~ such as heaters ~not shown), may also be utilized with horizonlal mixer lO in order to dry or heat the material being mixed. Access to the inside of chamber 12 is provided by access doors 22a, 22b which are hingedly coupled to the outside surface 23 of the cylindrical side wall of the chamber 12.
The inside surface 24 of the cylindrical side wall which defines inside space 15 is preferably polished so ~hat tile mixed ma~erial sl;des easiiy thereover for mixing and discharging as required. Chamber 12 is generally a large capaciry mixer in the range of approximately 300-30,000 lilers and therefore, the components of the mixer are expected to handle substantial mixing loads. The end walls 14a, 14b include respective teg extension portions 25a, 25b which are rnoun~ed on an appropriate support structure 26 for elevating the mixing chamber 12 and particularly he discharge ~ort 18 above a grolJnd surface. A!ternatively, mixer 10 mighl be moLInted directly on the ground as long as sufficient clearance of discharge port 18 is provided.
For mixing within space 15 of chamber 12, the horizontal mixer 10 of the invention further comprises a horizontal mixing shaft 30, having a longiludinal axis 31 which is horizontally disposed so that the shaft is preferably coaxially mounted wi~h Ihe cylindrically-shaped chamber 12. Shaft 30 is heavily cons~ructed for handling the large load mixin~ of horizontal mixer 10 and is preferably fabricated of 316 stainless steel having an outer diameter in the mixing chamber in the range of approximately 21/~
inches to 16 inches The length of the shaft ~0 will vary ~ith the capacity of the mixer ~0 As described further herein~elow, the . -- - '' '' '' ends of-the shaft 30 neck down to an outer diameter appropriale for coupling tO support and drive structures.
A plurality of mixing tools, such as mix;ng plows 32, are coupled to the shaft 30 by support arms 34 which are appropriately fixed or bolted to plow pockets 36 secured ~o shaft 30 (see Fig. 2~. Preferably, the mixing tools 32 are staggered both longitudinally on shaft 30 and also radially around shaft 30 as ~ppropriate to provide proper mixing. The support arms 34 and the mixing tools 32 are configured so that Ihe head or plow of Ihe rnixing tool sweep freel~t pas~ ~he polished inside surface 24 of the cylindrically-shaped chamber 12. The spacing of the tools 32 from the inside surface 24 is varied depending upon the ~ixing process.
In that way, the mixing tools can engage, move, and therefore mix the ma~erial in the chamber without leaving any residual material unmixed against the inside surface 24 of Ihe side wall. Therefore, proper spacing between the mixing tools 32 and s~rface 24 is desirable As may be app~eciated, the length of shaft 30 will inherently create a certain amount of deflection in the shaft 30 because it is supported only at its ends. The arnount of deflection and stress on shaft 30 will then deter~nine what kind of shaft - CA 02204321 1997-05-02~ ~

d,ameter is necessary for the desired deflection and proper spacing o~ the mixing tools during mixing. As may be appreciated, Ihe farther Ihe distance bet~veen the polnls of support at the ends of the shafT, ~he greater the amount of deflection and stress and thus the larger the shaft diameter required. Currently available horizomal mixers utilize heavily-designed, large diame~er shafts lo obtain the required deflection. However, such shafts are more expensive to fabricate and are also more difficult to seal given the larger diamet:er and the greater surface area ~hal must be sealed.
The present invention reduces the diameter of the shafl necessary ~o achieve rhe desired deflection as discussed below while providing impro~Jed sealing at the shafl ends.
Shaft 30 of the invention includes a driven end or drive end 40 and a non-dr;ven end or stub end 42 opposite the drive end 40. A drive motor 38 is operably coupled to a belt drive 43 which, in turn, is operably coupled to the shaft drive end 40 by an appropriate gear box and bearing structure 44. The ~ear box and bearing structure 44 will generall~ reduce the drive ratlo between Ihe drive rnotor 42 and shaft .~0. An elaborate dynam;c seal structure 46 is coupled to drive end 40 between the gear box and bearing structure 44 and the respective chamber end wall 14a.

The shaft drive end 40 protrudes through an appropriate opening 47 in end wall 14a while the stub end 42 protrudes through an appropriale opening 48 in the end ~,vall 14b.
The d~namic seal slr~Jcture 46 seals opening 47 to prevent the migra~ion of mixed material out of chamber 12 and into the atmosphere along the shaf~ 30 and through the opening 47 Seal struclL3re 46 may comprise a series of adjacent braided packing elemer!ts (not shown) and also may include an air line (not shown) for preven~ing leakage as discussed above. Furthermore, seal str~cture 46 preferably prevents any entry of foreign matter inlo Ihe m;xing chamber 12 through opening 47 Seal structure 46 is an appropriate dynamic seal for sealing Ihe shaft drive end 40 and the opening 47 while allowing rota~ion of the shaft 30. To that end, ~ealing struct~lre 46 m;ght also utilize appropriate air or fluid 1~ lines ~not shown) to rnaintain a vacuum or press~ri2ed environment wi~lin chamber 12 as necessary for properly mixing and con~aining the material in charnber 12.
As ill~lstrated in Fig 1, drive molor 38 is indirectly coupled to shaft drive end 40 by belt drive 43 and is positioned above the shaft drive end 40. However, for larger rnlxer applications and for a higher power drive motor, the drive rnotor 38 ~ CA 02204321 1997-05-02 mi~ht be directly coupled to shafl 30 by an appropriate gear and coupling structure, bearing structure, and a separate seal slructure.
Hori~ontal mixer 10 might also be utilized for granulaling material as it is mixed, To that end, hori20ntal mixer 10 might include chopper bl~des ~0 coupled to appropriate motors 51 for grinding, chopping and granulating the material during the mlxlng process.
Fig. 2 illustrates an enlarged view of the shafl stub end 42 o~ the present invention incllJding a structure constructed in accordance with the principles of the present invention for supporting the s~ub end 42 of shaft 30 and also sealing the - opening in end wall 14b. Referr;ng now to Fig. 3, the suppor~
structure 56 of the invention simultaneously seals and rotatably supports the shaft stub end 42 to prevent leakage and migration of the mixed material out of the chamber at the stl~b end and also to prevent the leakage and intro~uction of foreign ma~erial into the chamber Ihrough the ~tub end.
In accordance with one embodimen~ of the invention, the support structure 56 for shaft stub end 42 comprises a head pl~te 60 and a bearing housing 62. The bearing housing 62 supports and contains a sleeve bearing 64 which is preferab~y fabrica2ed of a low-friction composite material such as a carbon graphile fibers and polymide binder composite ma~erial available from HyComp of Cleveland, Ohio. A small diameler bearing portion 43 of the shafl stub end 42 interfaces and cooperates with sleeve bearing 64 for rotation of shaft 30 Head plate 60 is mounted to end wall 1 4b to seal the opening 48 and is held to end wall 14b by appropriate fas~eners, such as bolts 66. Bearing housing 62 which is s~ainless steel in , one embodirnent of the invention, is then, in turn, interfaced with and fastened to head plate 60, such as with bolts 68, An inside shoulder 69 of bearing housing 62 couples to an inward radial wall of head plate 60 at interface 70. A static seal structure or head seal 72, such as a r~bber O-ring, is positioned in a groove 71 . .
formed in housing 62 proxirnate interface 70. Static head seal 72 seals interface 70 and generally prevents any escape of vapors or mixing material from inside chamber 12. Similarly, rnigralion or leakage of foreign contaminan2s into the mixed material through interface 70 is also generally prevented.
Sleeve bearing 64 has an appropriale key formation 64a formed thereon which is received by a respective groove 62a in bearing housing 62. The sleeve bearing 64 is preferably ke~ fi~

the bearing housing 62 around ~he shaft stub end 42. In that wa~, as shaf~ 30 rotat.-s, ~he sleeve bearing 64 is maintained in place. A retaining ring 74 fits within an appropriate groove for~ned in bearing housing 62. Re~aining ring 74 confines the outside end 75 of the sleeve ~earing 64 to prevent the sleeve bearing from sliding longitudinally outwardly on the shaft stub end 42 during rotation. A shoulder 77 formed on bearing housing 62 further confines the sleeve bearing 64 a~ the inside end 79 of the sleeve bearing. During rotation of the shaft to nlix material within chamber 12, the shaft stub end 42, sleeve bearing 64 and bearing housing 62 may heated, cooled or at steady stated Bearing housing 62 will expand when heated and is preferably formed of 316 stainless steel and thus will expand substantially rnore than the composite sleeve bearing 64. Accordingly, the key fit of bearing 64 in ~he housing 62 and the retaining ring 74 and shoulder 77 ensure that the sleeve bearing is maintained within its optimat posi~ion with respec~ lo the shaft stub end 42 and housing 62.
For smoolh rotation and durability, the invention further comprises a hardened, wear-resistant sl~sve 76 which encircles a section of bearing portion 42 and is therefore disposed belween the shaf~ bearing portion 43 and the sleeve bearing 64.

Sleeve 76 is formed of a wear-resistanl material, such as 17-4 s~ainless sleel, and provides a contact surface for bearing 64 so that shaft bearing portion 43 is not worn during rotation of the shaft. A pluralily of set scre~vs 78 surround the stub end 42 and secure slPeve 76 to the shafl bearing por~ion 43. A slight gap 80 is maintained between Ihe sleeve 76 and shaft bearing portion 43 along a portion of the length of sleeve 76 to promo~e the sliding of sleeve 76 onto shaft bearing portion 4~ and the positioning of the sleeve thereon. Sleeve 76 thus rotates with shaft 30 and bears against the sleeve bearing 64 for rotational support.
Sleeve bearing 64 may be a continuous composite element as illustrated in Fig. 3 or may be a pluralit,r of adjacent elements positioned end to end. The unique support and seal structure 56 of ~he present invention including sleeve bearing 64 t 5 provides rotational s~pport of shaft 30 very close to the inside 15 of Ihe chamber. That is, shaft 30 is slJpported at a point very close to the end wall 14b and thus very close ~o Ihe main body of shatt 30. In that wa~, Ihe present invention significantiy reduces the amounl of space between the suppor~ed ends of the shaft and reduces the momenl forces on Ihe shaft The invention thus reduces the amount of deflection experienced bv a shaft 30 of a particular diameter as opposed to the subs~anlial deflection exp~rienced in prior arl configurations utilizing a separate ball-bearing or other bearing structure, ~hich is positioned to support shaft 30 a substantial distance away from end wall 1 4b and further ou~ on the reduced-diameter shaft slub end 42.
Therefore, Ihe shafr 30 rnay be made with a smaller diameter and still be able lo ~i~hstand the resullant mixing forces and onl~ def!ect the desired amo~nt This reduces the costs of fabricating the shaft and supporting and sealing the shaft and thus reduces the overall costs of the mixer.
Additionally, the composite slee~Je bearing 64 of the in~ention is a durable bearing structure which is relatively inex-pensive to fabricate. The sleeve bearing 64 provides proper rota-tional supporl of shaft 30 and is wear-resistant for reduced main-tenanc~. Also, the sleeve bearing does not include any additional moving components, such as ball bearings or roller bearings which are subject tO failure. Still further, the sleeve bearing of the inven-tion will not generally trap mixed material in the bearing s~ructure and thus ~ill reduce wear, corrosion and failure associated with trapped rnaterial. The reduction of the shaf~ size and weight also provides more uniform lengthwise contact between shaft shafl bearing portion 43 and the sleeve bearing 64 to prevent uneven wear of the sleeve bearing and to prolong its useful life.
ThP interface 82 between the shaft stub end 42 and sleeve 76 is sealed by an appropriaTe static sleeve seal structure ~4, such as a rubber 0-ring seal, which fits into an appropriate groove formed in the ;nside wall of sleeve 76. Static sleeve seal structure 84 seals interface 82 and prevents the migration or leakage of mixing rnaterial oul of chamber 12 along the shaft bearing portion/sleeve interface 82. Furthermore, contaminants are prevenled from leaking into the mixin~ chamber 1~ thro~ gh interface 82.
Further in accordance with the principles of the present invention, a stalic sealing suucture is used to seal the stu~
end 42 and prevent leakage bet~veen chamber space 15 and the outside atmosphere. The static sealing structure of the invention is not worn or affected by the rotational and translational movernent of the stub end of shaft 30.
Referring to Fig. 3, the horizontal mixer of the present invention cornprises a sealing shroud 100 which is generally positioned over a portion of the shaft stub end 42 and particularly over the shaft bearing por~ion 43. Sealing shroud 100 includes an annular lip or collar 102 for col~pling the sealing shroud 100 to . char~7ber end wall 14b, and more specifically, to the bearing housing 62 by appropriate fasteners, such as bol~s 104. A static shroud seal structure or seal 106, formed of a high temperature-resistanl ma~erial, such as VITON rubber, for example, is positioned between lip 102 and the outside end of the bearing housing 62 at the interface 63 therebetween. Shroud seal structure 106 and shroud 100 seal the shaft s~ub end 42 for pre~enting leakage between the atmosphere and chamber 12.
In one embodiment the shroud seal 106 is in the form of a gasket structure as shown in Figs. 3 and 4. The static shroud seal 106 is coupled between ~he bearing housing 62 and shroud 100 at interface 63, and is thus maintained out of direct contac with the ro~a~able shaft 30 Therefore, rotational or lateral movement of the shaft 30 does no~ affect the integri~y of the seal 106 by wearing on the seal 106. That is, there is no direct rotational or translational wear on seal 106 provided by rotating shaf~ 30. Therefore, shroud seal 100 does not have to be replaced as often as prior art dynarnic seals which leak due lo wear.
Furthermore, the sta~ic shroud and shroud seal are significantly less expensive to manufacture and thus to replace than prior art dynamic seals. The shroud 100 and staric shroud seal 106 of the inve~tion effectively seaJ the s~ub end 42 of shaft 30 to prevent leakage at the stub end between Ihe chamber and atmosphere.
The static seal ~nd shroud are durable and require very little rnainlenance, and any leakage through the stub end 42, such as through sleeve bearing 64 is contained by the shroud 100 and seal 106.
The unique shroud 100 and static shroud seal struct~re 106 of the present invention also effectively contain the vapors associated with the mixing process within a space confined between the sealing shroud 100 and the stub end 42 To further enhance vapor containment, sealing shroud 100 may include inlet and outlet fl~i~ ports 1 08a, 108b which are utiii2ed appropriatel~ to introduce or evacuate a fluid, such as a liquid or gas. For examp~e, water might be flushed into the inside of sealing shroud 100 to clean the shaft stub end 42, such as if leakage occurred through sleeve bearing 64. Alternatively, pressurized nitrogen (N2) might be utili~ed to create a pressure differential between the space 109 defined by se~ling shroud 100 and Ihe space 15 inside of chamber 12. The pressure in the shroud space 109, for example, would be maintained higher than the internal pr~ssure in the interior space 15 of chamber 12 thus f~lrther preventing any leakage or ~nigration of vapors and material out of chamber 12 through the interface of ~he sleeve bearing 74 and sleeve 76, or th~ interface of the sleeve 76 and the shaft bearing portion 43.
Since shroud seal 106 of the invention is a static seal, the vapor integrity of the horizontal mixer 10 of the present invention is not susceptible to the rotational wear or longitudinal wear from shaft 30. This pro~ides a significant advantage over the prior art which u~ilizes braided packing elements in a dynamic seal or precisely machined surfaces in mechanical seals which are all particularly susceptible to failure and leakage of bolh m;xed material and vapors due to rotation and translation of the shaft.
Therefore, maintenance on the mixer seal structures is further reduced. Wh~le pressurized fluids may be used ~Iv;th shroud 100 of the presenl invention, the shroud and shroud seal 106 effectively seal the s~ub end 42 wi~hout pressurized fluids.
Further in accordance with the principles of the present invention, the horizontal mixer 10 cornprises a dynamic seal structure or seal 90 which surrounds the shaft stub end 42 and more particularly surrounds bearing portion 43. The dynami seal structure 90 engages the ouler surface of bearing portion 43, or in the embodiment illuslrated in Fig. 3, the outer surface of wear-resistant sleeve 76. The dynamic seal structure 90 is positioned proximale the inside end 79 of sleeve bearing 64 which is conf;ned by shoulder 77 of the ~earing housing 62. The dynamic seal structure 90 engages the outer surface of sleeve 76 and provides a seal between sleeve bearing 64 and the inside a~e~ 15 of mixing chamber 12, Seal structure 90 is dynamicall~ operable and will seal the sleeve bearing from the inside of chamber 12 during rotation of shaft 30. Dynamic seal strucl~re 90 is utilized to prevent leakage through slee~e bear;ng 64 and thus improve the overall life of the sleeve bearing of the invention, Furthermore, the prevention of foreign materials be~een the shaft and sleeve bearing increases the life of the bearing, Referring now to Fig. 3A, an enlarged view of the dynamic seal struct~re 90 of the ernbodiment of the invention illustrated in Fig. 3 is shown. The dynamic seal structure 90 of one embodirnent of the invention is a lip seal design and comprises a pair of seal glands or elements 92a, 92b which abut each other and engage the rotating sleeve 76 of shaft 30. As illustrated in Fig.
3A, each of the sealing elements 92a, 92b is generally L-shaped having an inner portion 91 which extends generally parallel to the sleeve 76 and which engages sleeve 76, and an elongated outer portion generallv perpendicular to sleeve 76 which engages a metal case 94 The outer porlion 93 of the seal elements 92~, 92b are preferabiy pressure fitted Into appropriately formed grooves in the metal case 94. A gasket 95 lies between the sealing elernent 92b and case 94. An appropriate sealing structure is available from Parker Packing GMP of ~city,s~ate~ and includes a case 94 of 304 stainless steel, sealing elernents 92a, 92b of carbon fiber-filled teflon P8~7 and a gasket which is a flllorocarbon elastomer.
Dynamic seal structure 90, in combination ~rvith the sealing shroud 100, shroud seal 106 and sleeve bea-ing 64 of the invention provides a unique sealing and supporting structure 56 which adequately seals and supports the stub end 42 of the horizontal mixer 10. To further enhance the seal created by the dynamic seal structure 90, a spring device 97 may be used in conjunction wilh structure 90, such as around elemen~ 92a Spring device 97 further biases ~he element 92a against the sleeve 76 to enhance the seal. Dynamic seal s~ruclure 90 prevents the leakage of any mixed material out of chamber 12 and into contact with the sleeve bearing 64. [)~namic seal structure 90 further prevents contaminants, ~hich might seep or leak through the sleeve bearing 64, frorn entering chamber 12. Additionally, the dynamic seal ~trucl~lre ~0 generally prevents mixing rnaterial from ~nigrating to ~he interface between the sleeve bearing 64 and sleeve 76 thus prever~ting premature wear of the sleeve bearing 64 as mentioned above, The seal structure 90 is particularly durable and wear-resistant.
As discussed, the present invention requires less maintenance and is not subject lo the frequent seal failure and lea~age associated with prior art stub end seal structures Therefore, appropriate maintenance can be scheduled and the horizontal mixer 10 of the invention is not as prone to an unscheduled cessation of the mixing process which occurs with prior arl horizontal mixers. Furthermore, the invention does not require constant lubricating or grease packing as is necessary with other mixers using roller of ball bearings.
Accordin~ly, the present invention provides low maintenance and durable sealing and support of the stub end of a horizontal mixer shaft and thus eliminates the failure-prone sealing structures of Ihe prior art and the separate bearing structures utilized in conjunction ~vith the prior art dynamic seals.
furthermore, the unique cornbination of elements including the sleeve bearing, sealing shroud and shroud seal does not restrict the outerrriost end 98 of ~he shaft stub end 42. When the shaft 30 expands and contracls in length due the heat or cooling during mixing, the slub end will slide or Iranslate free~y left or right as illustrated in F~g. 3 by arrouv 99 with generally little or no effect on the operation of the shroud and shroud seal 90 and the slee~Je bearing 64.
Referring again to Fig. 1 the stub end 42 of shaft 30 would generally see the most longitudinal translation because the drive end 40 is fixed to the appropriate gearin~ and coupling box 44 so as to restrict mo~Jement at the dri~Je end. The shaft 30 expands and contracts and seals move back and forth on the shaft due to constant ~emperature variations in the shaft and chamber.
The charnber 12 is often heated and cooled. Furthermore, the shaft may be heated or cooled by introducing a liquid or gas into a cavity (not shown~ in the shaft. Also, the mixing process itself generates heat. The longitudinal expansion and contraction of the shaft provides translational mo~Jement of the shaft and thus wears the prior art dynamic seals coupled to the shaft stub end. The end walls of the chamber also rno~Je, providing additional wear on any stub end seal struc~ures.

Prior art dynamic seal and bearing structures at the ~rnixer stub end were therefore particularly susceptible to both rotational wear and IransJational ~ear as the shaft rotated and expanded and contracted longitudinally in length. The invention provides a horizontal mixer which is resistant to failure caused b~
rotationa~ and longitudinal rnovernent of the mixing shaft 30, beca~se the sealing shroud and static shroud seal are maintained away out of direcT contact with the shaft stub end 42. The sealing shroud is also dimensioned to allo~ such translational expansion.
Fig. 4 illustrates an allernative embodiment of the invention and comprises a bearing housing 120 which couples directly to an end wall 121 of a horizontal rnixing chamber To that end, the bearing housing includes a radial flange 122 wh;ch receives an appropriate bolt suucture or bolt 124 for securing the bearing housing 120 to the horizontal mixer. Bolt 124 is secured to end vvall 121, such as by a plug ~eld at the inside end 125. Nut structures 126 may be tightened on bolt 12~ to properiy seat the bearing housing 1 20. The end wall 1 21 includes an opening 1 28 through which the stub end 142 of shaf~ 130 extends. Adjacent the opening and surrounding Ihe opening, an annular shoulder 132 receives a horizontally projecting collar struclure 134 of the bearing housing 120. A static seal structure 1~6, such as an 0-ring, rests .within an annular groove formed in the annular collar structure 134.
Seal structure l 36 effectively seals the interface 1 37 and operates to prevent leakage at the interface into the a~mosphere.
The ernbodiment illustrated in Fig. 4 utilizes a wear resistant sieeve 176 similar to sleeve 76 illustrated in Fig. 3.
Sleeve 176 is fixedl,v secured to the shaft s~ub end by the se~
screws 178 and is sealed at its inside end by an appropriate static seal structure 184. A sleeve bearing 164 is securely key mounted within bearing housing 120 as discussed hereinabove and is longitudinally contained on the shaf~ by a shoulder 177 and a retaining ring 174 to prevent longitudinal movement along the shaft stub end 142 ~rvhen the stub end, bearing hol~sing 120 and bearing 164 expand due to the heat generated during the mixing process.
Sleeve bearing 164 is preferably a frict;on resistant cornposite as discussed hereinabove The embodiment illustrated in Fig. 4 utilizes a dynamic seal structure 190 which provides a dynamic seal proximate the inside end of the sleeve bearing lo prevent leakage of materials into and out of the horizon~al mixing chamber as discussed hereinabo~Je. The dyn~mic seal structure 190 further prevents rnalerials from migrating into the interface between sieeve bearing 164 and v~ear resistant sleeve 176 to thereby prevent premature wear of the bearing.
Referring ~o Fig. 4A, the dynamic seal structure 190 comprises a corrosion resistan~ metallic case 194 into which a wear-resistant seal element 192 is pressure fit againsl a gasket 195. A suitable dyna~Tic seal suuclure is available trom Parker Packing GMP and includes a case 194 of 3()4 stainless steel, a seal 192 of Ekonol filled Teflon and a gasket 195 which is a fluorocarbon elastomer.
The embodirnent illustrated in Fig. 4 ~urther comprises a sealing shroud 200 in accordance with the invention, which is mounted to bearing hol~sing 120 by appropriate bolt struct~res 204 which extend through openings in a lip or collar 206. The interface between the collar 206 and the bearing housing 120 is sealed by a static shroud seal struc~ure or seal 207, such as a high temperature-resistant gasket, to provide a seal at ~he s~ub end and thus contain any material or vapors which may pass from the chamber space 15 of the horizontal mixer and through the sleeve bearing and sleeve str~lctures at the shaft slub end 142. Ports 208a and 208b and sealing shroud 200 may be utilized to introduce a liquid or gas into space 209 defined between the sealing shroud 200 and the shaft stub end 142 as discussed hereinabove.
The embodiment of the invention illustra~ed in Fig. 4 has all the advantages of the ernbodiment illusuated in Fig 3 and provides a support and seal structure for the shaft stub end 142 which is low maintenance, durable, and adequately prevents leakage of the rnixed material or vapors to the atmosphere or contamination of the mixed material by an outside foreign contaminant, such as grease or oil. Furthermore, the shaft stub end 142 is unrestricted so that longitudinal expansion may occur without signi~icantly effecting the sleeve bearing 164 and the dynamic seal structure 190 of the invention.
Accordingly, the invention provides a horizontal mixer having an improved structure for sealing and providing rotation of the stub end of a horizontal mixing shaft which red~ces the maintenance required for the mixer and also reduces the cost and complexity of the mixer. The presen~ invention reduces the diameter of the mixing shaft to reduce costs The present invention includes a generally unitary bearing and seal combina~ion which is very durable and more resistant to failure from the rotational and longiludinal movement of the rotaling shaft than are the conventional separate seal bearing and structures utilize~ with prior art horizontal mixers.
While the present invention has been illustrated by a descriptlon of various embodimen~s and while these embodiments have been described in considerable detail, it is not the intention of the applicants to restric~ or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limite~ to the specific details, representative apparatus and method, and illustrative example shown and described. Accotdingly, departures may be made from such details without departing from the spirit or scope of applicant's general inventive concept.
What is claimed is: