Background of the Invention

1. Field of the Invention

This invention relates generally to a seal assembly for sealing rotary equipment utilized primarily in the dry- ing and cooling industry. More particularly, this in¬ vention pertains to a segmented seal for sealing the intake and discharge ends of steam tube and direct fire dryers and other types of rotary equipment including coolers which are commonly found in the grain process- ing and chemical industries.

2. Description of the Prior Art

The grain processing and chemical industries typically have a requirement for removing moisture from raw mate- rials, by-products and finished products. For example, brewers generate vast quantities of "brewers spent grains" which are a high moisture, high protein by¬ product of the brewing process. This by-product is useful in the cattle feed industry so long as the water is removed prior to feeding livestock. Consequently, cost-effective techniques of removing the moisture from such spent grains has been devised utilizing rotary steam tube dryers. Such dryers are comprised of a ro¬ tating cylindrical body having tubes disposed longitu- dinally therein which are charged with steam to elevate the temperature of the contents of the dryer for remov-

ing moisture therefrom by evaporation. Alternatively, the contents of the dryer are heated by direct exposure to a flame. This type of dryer is referred to as a di¬ rect fire dryer.

Common to all types of rotary equipment utilized in the grain and chemical industry for drying or cooling is a stationary intake housing for receiving the product. The dried product exits the rotary equipment into a stationary discharge housing. Consequently, prior art means have been devised for sealing the stationary in¬ take and discharge housings with respect to the rotat¬ ing cylinder so that the product to be dried is not lost or the efficiency of the equipment is not impaired.

Moreover, a pressure gradient often develops from the inside of the equipment with respect to the outside at¬ mosphere. These pressure gradients can be caused by velocity of the product within the equipment as well as by increases in the volume of heated, moisture laden discharge air. These pressure gradients exacerbate the problem of sealing the intake and discharge ends of the equipment as they can cause either undesirable loss of product through the seal, or alternatively result in excessive intake of air which reduces efficiency of the equipment.

Prior art seals are comprised of segmented articulated rings circumferentially disposed about the rotating cylinder and affixed to the stationary housing of rota¬ ry equipment. Said arrangement provides axial and ra¬ dial sealing with respect to the rotating cylinder. However, this prior art apparatus becomes ineffective as the axial and radial sealing surfaces undergo wear. Moreover, although the prior art does allow for limited

compensation for irregularities in the roundness of the rotating cylinder, such accommodation is reduced as the prior art apparatus wears with usage.

Additionally, where the rotary equipment relies upon exogenous heat for drying, said equipment undergoes substantial increases in dimension as its temperature becomes elevated. This thermal expansion results in the prior art seal having a maximal effectiveness in a limited temperature range while being less effective at temperatures outside of said range.

Therefore, it is desirable to provide a sealing assem¬ bly which accommodates wear along the axial sealing surface of the rotating cylinder as well as accommo¬ dates run-out due to irregularities in the roundness of the rotating cylinder's axial sealing surface. Furthermore, it is desirable to provide a seal assembly which operates at maximal efficiency at a wide range of operating temperatures and can accommodate concomitant wide ranging thermal expansion and contraction of the rotary equipment.

Finally, it is desirable to provide a seal assembly which minimizes the leakage of product or atmosphere at the axial and radial sealing surfaces where pressure gradients are likely to exist.

Summary of the Invention Therefore, it is provided in the practice of this in¬ vention according to a presently preferred embodiment a seal assembly for effecting a seal between a stationary housing and a rotatable cylinder comprising a plurality of arcuate segments radially disposed about the outer circumference of said cylinder. Each segment has an axial sealing surface defining a radius approximately

equal to that of the rotatable cylinder and additional¬ ly has an end section for overlapping adjacent segments thus creating a gap and radial interface between said adjacent circumferentially disposed segments. The sealing assembly additionally comprises means for seal¬ ing the gaps formed by the adjacent overlapping seg¬ ments, means for tensioning the segments radially about the outside circumference of the cylinder and means for removably attaching each segment to the housing while concurrently permitting radial displacement of each segment independently from its adjacent segments.

Brief Description of the Drawings

These and other features and advantages of the present invention will be better understood by reference to the following description when considered in connection with the accompanying drawings where:

FIG. 1 is an elevational view of a rotary steam tube dryer illustrating three separate sealing assemblies each constructed according to the principles of this invention;

FIG. 2 is an elevational view of a typical seal assem- bly taken along line 2-2 of FIG. 1;

FIG. 3 is a frontal view of a typical seal segment;

FIG. 4 is a rear view of a typical seal segment;

FIG. 5 is a plan view taken along line 5-5 of FIG. 4;

FIG. 6 is an enlarged cross-sectional view taken along line 6-6 of FIG. 2;

FIG. 7 is an enlarged cross-sectional view taken along line 7-7 of FIG . 2 ;

FIG . 8 is an isometric view of an elastomeric sealing block ; and

FIG. 9 is a plan view taken along line 9-9 of FIG. 2.

Description of the Preferred Embodiments FIGS. 1, 2, 3, 4, 5, 6, 7, 8 and 9 illustrate a pre¬ ferred embodiment of the seal assembly (10) constructed according to the principals of this invention. Three examples of the preferred embodiment (10) are shown uti¬ lized in conjunction with the typical rotary steam tube dryer (11). It is contemplated that other embodiments of this invention fall within its scope for applica¬ tions utilized in direct fire dryers, coolers and all types of rotary equipment employed in the grain pro¬ cessing and chemical industries for removing moisture by evaporative process or alternatively removing heat by convection, conduction and radiation. Moreover, it is anticipated that embodiments of this invention could be adapted to rotary equipment utilized in other indus¬ tries such as sewage treatment and cement manufactur¬ ing. These alternative industries also have an ongoing demand for rotary equipment and such equipment could be easily modified to incorporate the preferred embodiment of the seal assembly described and claimed herein.

FIG. 1 illustrates a rotary steam tube dryer (11) hav¬ ing an intake housing (12) which is supported in a sta¬ tionary position by an intake housing stand (14). A rotatable cylindrical portion or shell (16) is inter¬ posed between the intake housing (12) and a discharge housing (30) which is stationarily supported by a dis¬ charge housing stand (32).

The shell (16) is rotatably supported by two pairs of rolls (20) each pair of which is in turn stationarily supported by roll bases (18). Each pair of rolls (20) is rotatably coupled to a tire (22) affixed to each end of the shell (16). The shell is driven by a motor (24) which is coupled by a pinion gear (26) to a ring gear (28) which is affixed to the outer circumference of the shell (16).

The equipment is utilized by continuously rotating the shell (16) by means of the motor (24), and by charging steam tubes (not shown) disposed within the interior of the shell (16). After the equipment has reached proper operating temperature, the product desired to be dried is caused to enter the intake housing (12) on a contin¬ uous basis. The product is rotated within the shell and passes through the shell at a predetermined veloc¬ ity so that adequate drying time is provided.

The dried product then exits the shell (16) through openings (not shown) in the shell which openings are covered by the stationary discharge housing (30). The product is then conveniently collected from the dis¬ charge housing (30) for further processing.

As moisture is removed from the product by evaporation due to contact with the hot steam tubes and other heat¬ ed surfaces, the volume of gases within the shell (16) increases causing a pressure gradient with respect to the outside atmosphere. Gravity as well as the pres¬ sure gradient from the inside to the outside of the shell would cause material to be lost at the margin be¬ tween the rotating shell (16) and the stationary dis¬ charge housing (30) if such circumferential margin were not properly sealed. The seal disposed at the dis-

charge housing (30) requires two separate seal assem¬ blies (10), one distal and one proximal to the discharge end of the shell.

Additionally, a seal assembly (10) is required between the intake housing (12) and the intake end of the shell (16). This seal assembly functions to prevent waste and spillage of the product through the gap between the intake housing (12) and the intake end of the shell (16). Said loss is occasioned by gravitational forces and pressure gradients that may develop at the intake end of the shell.

FIG. 2 illustrates an example of the preferred embodi- ment of the seal assembly (10) constructed according to the principles of this invention. Said illustrated seal assembly (10) is the assembly proximal to the dis¬ charge end of the shell (16). However, the discharge housing (30) seal (10) distal to the discharge end of the shell (16) is identical in construction to that il¬ lustrated. Moreover, the seal assembly (10) disposed at the intake end of the shell (16) is also identical in construction to that illustrated in FIG. 2.

A plurality of arcuate segments (40) are circumferen¬ tially disposed about the outside circumference of the shell (16) by affixing them to a seal mounting ring (34). Said mounting ring (34) is preferably welded to its associated discharge (30) or intake (12) housing. Alternatively, said mounting ring (34) may be bolted or otherwise removably affixed to its appropriate housing to permit proper installation and periodic adjustment if required. Said ring (34) and said housings (30) and (12), respectively are preferably constructed from fer- rous materials to facilitate ordinary arc welding and the like.

The segments (40) are constructed from nonferrous mate¬ rial such as epoxy impregnated cloth or fiberglass. Sythane-Taylor (Philadelphia) Synthane" is preferably utilized. Alternatively brass, bronze. Teflon, plastic or other bearing material may also be utilized.

Each arcuate segment (40) is mounted to the seal mount¬ ing ring 34 by means of a stud (44) which is fixidly attached to said mounting ring (34). Said attachment is accomplished by welding to or by threaded coupling with the mounting ring (34). Each stud (44) passes through an elongated stud slot (42) defined by each seal segment (40). A doughnut shaped elastomeric bush¬ ing (48) , having a steel washer disposed on either side of said bushing (48) , is interposed between said seal segment (40) and a nut (46). Said nut (46) cooper¬ atively engages the threads of the stud (44) and is ad¬ justed with sufficient torque such that adequate pressure is developed within the elastomeric bushing (48) with a component coaxial to the stud (44). Said coaxial pressure provides adequate force to maintain a radial seal between the radial seal surface (110) of the segment (40) and the seal mounting ring (34).

Elastomers as used herein include materials preferably selected from the group consisting of styrene-butadiene rubbers, natural rubbers, cis-polybutadiene rubbers, cis-polyisoprene rubbers, ethylene-propylene rubbers, butyl rubbers, polyacrylates, polysulfide rubbers, sil- icones, fluorocarbons, neoprene, nitrile rubbers, poly- urethanes and other elastomers.

The elongated slot (42) defined by the segment (40) is aligned radially with respect to the arcuate axial sealing surface (100) of the segment (40). The radius

of the axial sealing surface (100) is selected to be approximately equal to that of the shell (16) and thus said arcuate axial sealing surface (100) comprises a portion of the total axial seal of the seal assembly (10). The length of the slot (42) is selected to allow sufficient radial displacement of the segment (40) to accommodate anticipated or measured irregularities in the roundness of the shell (16) as well as to accommo¬ date wear to the seal segments (40) along their axial sealing surfaces (100). FIG. 6 illustrates with refer¬ ence characters "X" and "Y" the relative range of trav¬ el of an out of round or "egg shaped" shell (16) that can be accommodated by corresponding radial displace¬ ments of the seal segment (40) and associated slot (42).

Each segment (40) additionally defines a first overlap section (102) and a second overlapping section (104). Said sections preferably have a thickness of approx- imately one-half the thickness of the segment (40) in the vicinity of the slot (42). The first and second overlap sections (102) and (104), respectively, are de¬ signed to overlap the second and first sections (104) and (102), respectively, of adjacent segments (40). The width of said sections (102) and (104) is also se¬ lected to accommodate wear of the arcuate axial sealing surface (100) which results in gradual inward radial displacement of the segments.

Said first and second overlap sections (102) and (104) , respectively, additionally define first and second ra¬ dial lap sealing surfaces (106) and (108), respective¬ ly, which contact second and first radial lap sealing surfaces (108) and (106), respectively, of adjacent segments (40). Said lap sealing surfaces (106) and

(108) comprise an integral part of the radial seal provided by the seal assembly (10).

First and second seal block seats (112) and (114), re- spectively, having a square or rectangular cross sec¬ tion in the plane of the segment (40) are defined within each seal segment (40) along its outer radius. The location of said first and second seats (112) and (114), respectively, is selected to align with the gaps (103) formed by adjacent first and second overlap sec¬ tions (102) and (104), respectively, of adjacent seg¬ ments (40). Disposed within each complete seal block seat formed by the combination of adjacent segments (40) and associated adjacent first and second seal block seats (112) and (114), respectively, is an elast¬ omeric seal block (64).

Said seal block (64) is selected to have a thickness less than or equal to the thickness of the segment (40) in the vicinity of the slot (42). The width of the block (64) selected to provide adequate sealing at the point of the gap (103) formed by the adjacent segments (40). The width is also selected to not interfere with the radial displacement of the segments (40) throughout their entire range permitted by the length of the elon¬ gated slot (42). Said width is also selected to accom¬ modate wear along the arcuate axial sealing surface (100) of the segments (40) permitting their gradual ra¬ dial displacement inwardly toward the longitudinal axis of the shell (16) .

A cable alignment groove (54) is defined by each ar¬ cuate segment (40) along its outer circumference for aligning a cable (52) each end of which is attached to an associated anchor bracket (38) through an associated turn buckle (56) and spring (58).

Said anchor brackets (38) are preferably comprised of ferrous metal and attached in the vicinity of each of the upper corners of the associated intake (12) or dis¬ charge (30) housing by arc welding or other means. One end of the cable (52) is coupled to one of the anchors (38) through a spring (58) and turnbuckle (56). Said turnbuckle (56) has hooks disposed at each end, one passing through an anchor hole (39) defined by its as¬ sociated bracket (38) and the other passing through a hook (59) formed by one end of the spring (58). The other end of the spring (58) defines a second hook (59) which passes through a loop in the end of the cable (52) which is formed by a clamp (53).

The other end of the cable (52) is similarly anchored to the second anchor bracket (38) with the addition of an eyebolt (60) through which one hook (57) of the turnbuckle passes. Said eyebolt (60) has a threaded portion which passes through an anchor hole (39) de- fined by the bracket (38). Disposed on either side of the bracket is a nut (62) for removably attaching said eyebolt to said bracket (38). This arrangement allows the distance between the opening defined by the eyebolt (60) the bracket to be adjusted. Said adjustment en- sures that the cable (52) does not contact itself at the point where it crosses itself.

A feature of the preferred embodiment provides that the cable (52) almost completely surrounds the entire seal assembly without rubbing against itself at the point of cross over. The cable (52) is threaded through a cylin¬ drical sleeve (66) passing through each seal block (64). The tension (58) created by the springs (58) and the cable (52) creates a radial component along the circumference of the seal assembly (10) which is trans-

itted to said seal assembly through the seal block

(64). The cable tension created by the springs (58) is adjusted by appropriate adjustment of the turnbuckles

(56).

Said cable tension has a two-fold purpose. First, it serves to ensure that each segment (40) has an adequate radial force factor to ensure that said segment (40) is properly seated against the axial sealing surface of the shell (16). Second, said radial force ensures that each gap (103) is properly sealed by its associated sealing block (64) to perfect a complete axial seal.

The described embodiments of the invention are only considered to be preferred and illustrative of the in¬ ventive concept. The scope of the invention is not re¬ stricted to such embodiments. Various and numerous other arrangements may be devised by one skilled in the art without departing from the spirit or scope of this invention. For example, it is contemplated that the elastomeric bushing (48) disclosed herein could be sub¬ stituted with a spring or the like to provide adequate force to perfect the desired radial seal.

Moreover, means for tensioning the cable (52) could al¬ ternatively comprise weights coupled to the ends of the cable by means of pulleys. Additionally, the number of segments to be employed can vary depending upon the outside dimension of the shell. For instance, larger shells would require a greater number of segments than smaller ones. Where small deviations in the roundness of the shell (16) are expected, however, fewer arcuate segments having a concomitantly longer cord length may be utilized as anticipated displacement of the segments is reduced.

Finally, where additional seal capability is required, the axial and radial sealing surfaces can be greased.

Such application of lubricant further enhances the seal's ability to withstand pressure gradients as well as lubricates the axial and radial surfaces which are subject to wear.