Just-in-time bulk rubber bale processor

Information

  • Patent Grant
  • 6766721
  • Patent Number
    6,766,721
  • Date Filed
    Tuesday, November 26, 2002
    21 years ago
  • Date Issued
    Tuesday, July 27, 2004
    19 years ago
Abstract
A bale processor for cutting or dicing a bale or slab of unvulcanized rubber produces small cubes or blocks of a predetermined size and uniform shape for continuous feeding at a predetermined rate into a mixing machine or blender. A bale or slab of feedstock rubber is advanced incrementally along a slider platform and a segment is sliced from the leading end of the bale. After separation, the segment falls onto a receiving panel from which it is transferred by a vacuum pick-up head to a vacuum hold-down table. Multiple slices are then formed through the segment along the X-axis by circular cutting blades of an X-axis cutter head, thereby forming elongated segment strips. Next, multiple slices are formed through the segment strips in the Y-direction by a Y-axis cutter head which includes circular cutter blades that are extendable and retractable along the Y-axis. The bulk slab or bale is thus reduced to multiple cubes of predetermined length, height and width dimensions as established by the dimension of the initial segment slice and by the spacing of the circular cutting blades of the X-cutter head and the Y-cutter head, respectively.
Description




BACKGROUND OF THE INVENTION




The present invention relates in general to the processing of bulk unvulcanized rubber material, and in particular to a bale processor for cutting or dicing a bale or slab of unvulcanized elastomer such as ethylene propylene diene terpolymer (EPDM) or styrene butadiene (SBR).




Bulk synthetic rubber such as unvulcanized elastomer is normally supplied in a dense rubber bale or slab, typically 24″×18″×8″ size and 24 kg weight, often wrapped in a thin protective plastic film. Due to its high bulk density and compact size, the bulk rubber bale or slab is the most economical and safe form for shipping, storage and handling.




The term rubber as used herein refers to a natural rubber or polymer resin having in its unvulcanized state properties of deformation upon stress and recovery upon release of the stress. A rubber can be further defined as having a glass transition temperature of below 20° C. Most rubbers have a raw polymer Mooney value of from about 20 to about 125 measured at 100° C. (212° F.) after 4 minutes using a large rotor, i.e. a ML-4 reading, and have an elongation at break of from about 100 percent to about 1000 percent or more.




Examples of unvulcanized bulk rubbers that can be processed by the present invention include natural rubber, polyvisoprene rubber, polybutadiene rubber, cis-polybutadiene rubber, polychloroprene rubber, polysulfide rubbers, polypentenamer rubbers, polyacrylated rubbers, poly(butadiene-acrylonitrile) rubbers, poly(isopreneacrylonitrile) rubbers, poly(styrenebutadiene) rubbers, poly(isoprene-styrene rubbers) poly(ethylene-propylene-diene) rubbers, and the like. The term rubber as used in this invention also includes blends of two or more of the elastomers. The rubbers may be blended with resins or fillers prior to forming the bale or slab.




In recent years, the use of thermoplastic elastomers (TPE), which are melt-mixed blends of thermoplastic resins such as polypropylene and synthetic elastomer, is increasing rapidly. Blends of thermoplastic resin, elastomers, plasticizers or softeners, fillers and stabilizers offer significant advantages over thermosetting elastomers, including 100% recyclability, ready-to-use pelletized form, no need for curing, lower density, ease of processing, lower cost per unit, and colorability.




Thermoplastic elastomers are produced using either an internal batch mixer or continuous mixers. In recent years, many producers of TPEs have used continuous mixers because of their ability to provide uniform product quality, short residence time and versatility. Various ingredients are metered directly through small input openings in the continuous machine using automatic feeding devices. For consistent feeding and trouble-free operation, all ingredients must be small in size, uniform in shape and non-agglomerating in nature. Since a rubber bale is very large, it must be reduced to pieces or fragments that are size-compatible with automatic feeding equipment and other ingredients. Even in a batch mixer, where whole dense bales can be used, smaller size feedstock reduces cycle time and hence reduces overall productivity and quality of product. In making rubber-based adhesives, smaller size rubber feedstock enhances the rate of solvent diffusion.




Various devices including guillotine cutters, granulators and shredders use rotary knives, shears or saw blades for comminuting and reducing the size of scrap plastic and rubber. For example, U.S. Pat. No. 4,280,575 discloses a machine for cutting and metering a slab of unvulcanized rubber, which utilizes a continuous blade band sawing machine for cutting slices of rubber. U.S. Pat. No. 4,929,086 discloses a shredding machine which uses a rotary screw blade equipped with both radial and longitudinal knives for cutting shreds of polymer from a feedstock bale.




Such machinery is not suitable for dense bales of rubber because (1) unvulcanized rubber tends to flow under the influence of shear; (2) such machines are large in size, require special installation, use large amounts of energy, create loud noise, break down frequently, and require time-consuming cleaning; and, (3) the resulting product is either very large in size (e.g. as produced by guillotine cutters) or consists of a mixture of fine powder, fluff and large irregularly shaped chunks that are not suitable for continuous feeding applications. Moreover, the reduced material tends to stick and agglomerate, and has limited shelf life. Such machines are intended for large scale operation in production environment only and not suitable for small scale operations (i.e. lab scale devices).




Some producers of thermoplastic elastomers use a two-step method in which elastomer bale material is mixed with thermoplastic resin using an internal mixer, and reduce the size of the mixed material into pellets using an extruder-pelletizer or dices using a roll mill-dicer. Besides being a costlier process, there are other limitations to that conventional process: (1) the rubber material is subjected to two heat and shear steps which affects its durability; (2) many high molecular weight elastomers are highly oil extended which requires long mixing times; (3) are applicable only where the formulation consists of a large amount of thermoplastic resin; (4) the resulting pellets or dice must be dusted with a partitioning agent to keep them from re-agglomerating during handling; and (5) such pelletized materials have short shelf life and tend to agglomerate when stored under hot and humid conditions.




Some producers of elastomers provide rubber bales in form which can easily be broken into small popcorn-like crumbs. Even though very beneficial, such feed stock also has significant limitations: (1) crumbs with irregular surfaces tend to have very low bulk density and do not feed well using conventional feeders; (2) the crumbs tend to interlock in the feed hopper causing feed-blocking; (3) the crumbs do not pack efficiently and thus require large storage space; (4) only those elastomers with medium molecular weights, high co-monomer content and no oil are available in the form of dense bales; and (5) adding oil during mixing reduces shear, prolongs mixing time, and thus reduces production rates.




Most recently, some producers using new catalyst technology are supplying selected grades in free-flowing granular or large pellet forms. Currently, only a small range of some selected elastomers are available in the free-flowing granular shape, and none with any oil.




From the above discussion, it is clear that the baled elastomer must be reduced in size, preferably to portions of uniform size and shape to accommodate the needs of continuous mixing processes. The conventional reduction methods discussed above have one or more of the following limitations:




(1) high cost of size reduction equipment;




(2) irregular shape and size of resulting product not suitable for continuous feeding;




(3) lower bulk density of reduced product requires larger storage area;




(4) limited shelf life;




(5) requires unwanted partitioning agents to extend shelf life; and,




(6) size reduction method poses limitations on choice of elastomer and mixing method.




BRIEF SUMMARY OF THE INVENTION




Small cubes or blocks of a predetermined size and uniform shape are reduced from a bale or slab of unvulcanized rubber for continuous feeding at a controlled rate into a mixing machine or blender along with compounding chemicals during the mixing and extrusion of synthetic rubber and elastomeric products. A bale or slab of unvulcanized rubber is advanced along a loading platform on the input end of a processor console. The bale is fed incrementally into a first cutter assembly at a first cutter station where a segment of predetermined width is sliced from the leading end of the bale. The segment is transferred by a vacuum pick-up head to a second cutter station where it is secured for further reduction on a vacuum hold-down table.




After the segment is immobilized on the hold-down table, it is then sliced into elongated, parallel strips by an X-axis cutter head which includes an array of rotary cutter blades that are extendable and retractable across the segment in parallel with the X-axis. While the reduction strips are firmly held in place on the vacuum hold-down table, they are diced by a Y-axis cutter head which includes an array of rotary cutter blades that are extendable and retractable across the elongated strips in parallel with the Y-axis.




The slab segment is thus reduced to multiple cubes of predetermined length, height and width dimensions as established by the initial segment slice dimension and by the spacing of the roller cutting blades in the X-cutter head and the Y-cutter head, respectively. The bale is advanced incrementally at the speed demanded by the blending process, so that feed stock cubes are continuously transferred at a controlled rate to the feed throat of a mixing or shaping machine such as an extruder or internal mixer.











BRIEF DESCRIPTION OF THE DRAWING




The accompanying drawing is incorporated into and forms a part of the specification to illustrate the preferred embodiments of the present invention. Various advantages and features of the invention will be understood from the following detailed description taken in connection with the appended claims and with reference to the attached drawing figures in which:





FIG. 1

is a right side perspective view of a bale processor constructed according to the present invention;





FIG. 2

is a top plan view thereof;





FIG. 3

is a right side elevational view thereof;





FIG. 4

is a left side perspective view thereof;





FIG. 5

is a left side perspective view thereof with the frame partially assembled;





FIG. 6

is a sectional view, partially broken away, of the cutting blade assembly shown in

FIG. 1

;





FIG. 7

is a simplified, perspective view of a rubber bale or slab from which a segment has been sliced during the cutting step of the invention;





FIG. 8

is a flow chart which illustrates the principal steps of the invention; and,





FIG. 9

is a right side perspective view of a bale processor which includes a continuous band saw cutter.











DETAILED DESCRIPTION OF THE INVENTION




Preferred embodiments of the invention will now be described with reference to various examples of how the invention can best be made and used. Like reference numerals are used throughout the description and several views of the drawing to indicate like or corresponding parts.




The bale processor of the present invention is designed to continuously cut dense bales of unvulcanized rubber/synthetic elastomer into small size, regular and uniformly shaped cubes.




Referring now to

FIGS. 1

,


2


and


3


, in particular, a bulk rubber processing unit constructed according to the present invention is generally designated by the numeral


10


. The bale processing unit


10


includes a console


12


which is advantageously made up of rectangular perimeter side members


14


,


16


made of narrow gauge steel or aluminum angle stock, for example. The console


12


is stabilized by cross-bars


18


,


20


,


22


and


24


. Brace plates


26


are suitably secured to the perimeter members, such as by mechanical fasteners or welding, at the delivery end and loading end of the console.




The end braces


26


are adapted to journal an axle for corner support wheels. Conventional caster wheels W are secured to the perimeter frame members at the respective corners of the console at which the end braces


26


are attached.




The bale processing assembly


10


is portable so that it can be positioned in line with a conveyor belt or a weigh bin for transferring reduced rubber product at a controlled rate to the feed throat of a mixing or shaping machine such as an extruder or internal mixer. For this purpose, the console


12


is equipped with lockable wheels W which permit rolling movement of the bale processing unit


10


from one workstation to another. After the portable bale processing unit has been positioned correctly, its wheels W are locked by depressing wheel locking arms, and the bale processing equipment carried on the console


12


is made ready by an attendant.




The console


12


provides stable support for the bale processing steps in which a segment portion


32


on the leading end


34


A of a rubber bale


34


is sliced through a vertical plane as shown in FIG.


6


and then parallel slices are formed through the segment in the X-direction and Y-direction as indicated in FIG.


7


.




The console


12


also supports an operational deck


28


which is elevated above a drop space


30


. The console


12


further supports a bale loading platform


36


which extends from the rear end of the console


12


.




The console


12


further supports a cutter


38


in the form of a guillotine blade assembly


39


which is mounted on top of the console


12


at the delivery end of the bale loading platform


36


. In an alternative embodiment, the cutter assembly


38


includes a continuous blade band saw cutter


41


, as shown in FIG.


9


.




An X-Y cutter assembly


40


is mounted on the delivery end of the console


12


, directly overlying the drop zone


30


. A vacuum hold down table


42


is mounted beneath the X-Y cutter assembly, directly over the drop zone


30


and aligned in coplanar relation with the surface of the operational deck


28


. The vacuum hold down platform


42


preferably consists of two sections,


42


A,


42


B that are independently coupled by hinges to the console and are selectively extended and retracted by a double acting linear actuator


43


for discharging reduced segment product into the drop zone


30


. Optionally, the hold down platform


42


consists of a single platform section, as shown in

FIG. 9

, which is coupled by a hinge for pivotal swinging movement from a horizontal support position to an inclined discharge position.




Referring to the flow chart of

FIG. 8

, the bale


34


is advanced along the loading platform


36


, and a segment


32


is sliced from the leading end


34


A of the bale. After separation from the bale, the segment


32


falls flat onto the operational deck


28


, where it is picked up by a vacuum pick-up head


44


and transferred to the vacuum hold-down table


42


. Multiple slices are then formed along parallel lines


46


through the segment


32


along the X-axis by the X-cutter head


48


which includes a gang of circular cutting blades


50


that are movable along the X-axis. Next, multiple slices are formed along parallel lines


47


through the segment


34


along the Y-axis by a Y-axis cutter head


52


which includes circular cutter blades


54


. According to this arrangement, the slab segment


32


is reduced to multiple cubes


60


of predetermined length, height, and width dimensions as established by the spacing of the circular cutter blades


50


,


54


of the X-cutter head


48


and Y-cutter head


52


, respectively.




The foregoing steps are performed by components which are supported on the console


12


as follows. The bale loading platform


36


includes a movable fence


62


for advancing the bale along the longitudinal axis of the load platform toward the guillotine assembly


38


. The guillotine assembly


39


includes a fixed stop fence


56


for properly indexing the leading end


34


A of the bale as it is advanced into a cutting zone Z. The guillotine assembly


39


includes a pneumatic or hydraulic ram


64


that drives a shear blade


66


. The ram and blade are mounted on a support frame composed of side support panels


68


A,


68


B and a top support panel


68


C. The shear blade


66


is guided for vertical extension and retraction within a pair of guide channels


70


,


72


along the side support frame panels


68


A,


68


B, respectively. The guillotine blade


66


is extended and retracted along the guide channels by a piston rod


74


which is actuated as the hydraulic ram is switched.




When segment slices smaller than ⅜ inch are desired, the segments are preferably cut by the continuous band saw cutter of FIG.


9


.




As each segment


32


is sliced from the leading end of the bale


34


, they fall or are pushed over onto the receiving panel


28


below the vacuum pick-up head


44


. The vacuum pick-up head is extended and retracted along an overhead rail


76


by an air cylinder


78


. The vacuum pick-up head includes multiple suction cups


80


which are extendable into engagement with the slab segment upon extension of an air stroke cylinder


82


. After the segment has been engaged, the air cylinder


82


is retracted and the vacuum pick-up head along with the segment


32


is transferred along the overhead rail to a position overlying the vacuum hold down table


42


.




After the sliced segment


32


has been placed onto the vacuum hold down table


42


, the segment is immobilized and held in place on the table by the pressure differential exerted as ambient air is pulled through the inlet openings


84


.




The vacuum hold down table


42


is supported in coplanar relation with the receiving panel


28


and includes multiple air inlet openings


84


for drawing in ambient air. The vacuum hold down table is coupled to an air suction pump (not shown).




The segment


32


is further reduced by forming multiple slices through the body of the segment in the X-direction, as indicated in FIG.


7


. This cutting step is performed by the circular cutting blades


50


of the X-cutter head


48


. The circular cutting blades can be fixed or rotary. The X-cutter head is movably mounted for extension and retraction along the overhead rail


76


in parallel with the X-axis, as shown in FIG.


1


and FIG.


7


. The X-cutter head is driven by the double-acting air cylinder


78


. The elevation of the circular cutting blades on the X-cutter head relative to the hold down table


42


is set to perform clean slicing action through the segment, without scoring the vacuum hold down table.




Referring again to FIG.


1


and

FIG. 7

, the multiple slices in the Y-direction are performed by the Y-cutter head


52


. The Y-cutter head is mounted on a double-acting rodless air cylinder


86


for extension and retraction along the Y-axis. The double-acting air cylinder


86


is supported on opposite ends by double-acting air cylinders


88


and


90


, respectively. According to this arrangement, the Y-cutter head is retracted out of the way while the X-cutter head is performing its slicing operation. After the X-cutting operation has been completed, the X-cutter head is extended all the way forward toward the front end of the console (FIG.


4


), to permit the Y-cutter head


54


to perform its operation without interference. The Y-cutter head


54


is extended downwardly into engagement with the segment and then either extended or retracted along the Y-axis, and the Y-slicing operation is then completed.




A bale or slab


34


of dense rubber is manually or automatically loaded on the platform


36


, and is pushed by the fence


62


which is moved manually or by a stepping motor M and screw drive such that bale's leading edge


34


A advances incrementally into the cutting zone Z by a distance ½ inch (for a guillotine cutter) or ⅛ inch (for a band saw cutter) equivalent to desired height of the cube


60


. The hydraulic ram


64


drives the guillotine blade


66


, thus cutting thin segments


32


from the rubber bale. A special attachment to the cutter assembly separates each segment


32


from the blade and allows it to fall flat on the receiver platform


28


.




The segment


32


is lifted by the air suction cups


80


and is transferred to the perforated hold down platform


42


in X-direction by a


20


″ stroke rod-less air cylinder to a position under the bank of rotary cutting wheels


50


. The distance between the cutting wheels is adjustable from ½ inch to ⅜ inch and is equivalent to the desired width of a reduced cube


60


. The segment


32


is immobilized and held down by vacuum applied through holes in the platform. This set of cutting wheels cut the segment into strips.




The circular cutting wheels are separated by a ¼ inch solid washer and ¼ inch spring. By tightening the nuts, the distance between cutting wheels can be adjusted ½ inch to ⅜ inch. The springs also allow the circular cutting blades to adjust under mechanical force or heat without undue damage.




Optionally, the shaft of the circular blade


66


is cooled with recirculating water to keep the cutting blade from overheating. Moreover, a noise barrier blanket is placed around the guillotine to reduce “hissing noise” as pressurized air is released when the pneumatic cylinders are actuated.




A dispenser (not shown) sprays talc or similar fine-sized powder to keep the reduced cubes from sticking to each other when they are to be stored for later use.




When the second set of circular cutting blades reaches the opposite side in Y-direction, a switch triggers and opens the perforated hold-down platform sections


42


A,


42


B of the hold-down table. This allows the elastomer cubes


60


to fall through the drop zone


30


into a weigh bin or conveyor belt from which the cubes are mechanically transferred at controlled rate to the feed throat of a mixing or shaping machine such as an extruder or internal mixer.




The bale processor of the present invention provides a simple but unique method for solving the bale reduction problem. The just-in-time bale processor not only overcomes most of the limitations of conventional reduction equipment but also offers significant performance advantages. Because its small size and simplicity, the bale processor does not require large capital investment and is adaptable to large as well as small lines with an output rate of 10 kg/hour or more. The output rate can be increased by using multiple guillotine or saw blades. The bale processor is small in size and does not require any major installment and can easily be moved from station-to-station and placed in-line. It accommodates normally available dense bales of any molecular weight, with and without oil extension, irrespective of type of elastomer, and does not pose a noise problem. It produces small cubes of uniform size suitable for continuous feed processes. Moreover, its “just-in-time” size reduction capability eliminates the requirement for inventory of materials with low shelf life.




The bale processor of the present invention is portable, self-contained, free-standing and does not require any major installation except an electrical power connection. It can be used with any kind of unvulcanized rubber. Softness or density is not a limiting factor. The cutter may be modified to use a high-speed laser cutter or an electrical resistance wire (hot Nichrome wire) cutting under a nitrogen blanket, which does not generate any noise, and minimizes degradation. The bulk slab material is cut in specific cubes of uniform size, which are easy to feed in precise amounts, using “loss-in-weight” type belt feeders. The slab material is cut at the speed demanded by the process and hence does not require storing or dusting. The process can be fully automated to make it an unmanned operation. Since only a small amount of material is cut, there is no waste. It will cut virgin rubber without contamination, and it will not require post-process cleaning.




Some significant advantages to the compounding industry include elimination of pre-mixing of rubber bale using internal mixers which introduce unnecessary thermal history; avoids the use of expensive heat stabilizers; reduces inventory and handling of unfinished goods; formulators can use a wide range of elastomers; the simplified bale reduction process reduces direct labor cost by eliminating two-step processes; increase in capital utilization; and starting capital cost is reduced.




Although the invention has been described with reference to certain exemplary arrangements, it is to be understood that the forms of the invention shown and described are to be treated as preferred embodiments. Various changes, substitutions and modifications can be realized without departing from the spirit and scope of the invention as defined by the appended claims.



Claims
  • 1. Apparatus for processing a bale or slab of material into cubes or blocks having first, second and third side dimensions comprising, in combination:a loading platform for receiving a bale or slab of material to be processed into cubes or blocks having first, second and third dimensions; a first cutter for cutting the bale or slab to produce a single segment that has one side dimension which corresponds in size with the first side dimension of the cubes or blocks; apparatus disposed proximate the loading platform for incrementally advancing the bale or slab relative to the first cutter by a first distance that corresponds with the first side dimension of the cubes or blocks; a hold-down table; means for transferring the segment to the hold-down table including a suction cup and a suction source coupled to the suction cup for lifting the segment and then placing the segment on the hold-down table; a second cutter for forming multiple slices through the single segment along a first axis in which the slices formed by the second cutter are spaced apart by a second distance that corresponds to the second side dimension of the cubes or blocks, thereby reducing the segment to a plurality of elongated strips; and a third cutter for forming multiple slices through the elongated strips along a second axis that extends transversely with respect to the first axis in which the slices formed by the third cutter are spaced apart by a third spacing distance that corresponds to the third side dimension of the feedstock cubes or blocks.
  • 2. The apparatus of claim 1, further comprising means for immobilizing the segment on the hold-down table while the slices are formed by the second and third cutters.
  • 3. The apparatus of claim 2, wherein the immobilizing means comprises openings in the hold-down table and suction means for drawing air through the openings.
CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 09/561,672 filed May 1, 2000, U.S. Pat. No. 6,487,949 issued Dec. 3, 2000.

US Referenced Citations (14)
Number Name Date Kind
2282546 Schwimmer May 1942 A
2889878 White et al. Jun 1959 A
3333494 Smith Aug 1967 A
3385336 Barnard May 1968 A
3990336 Soodalter Nov 1976 A
4040318 Makeev et al. Aug 1977 A
4043231 Friedberg Aug 1977 A
4136749 Di Rosa Jan 1979 A
4280575 Di Rosa Jul 1981 A
4909139 Montano et al. Mar 1990 A
4929086 Geyer May 1990 A
4991477 Butt et al. Feb 1991 A
5410954 Wygal et al. May 1995 A
6487949 Dharia Dec 2002 B1
Continuations (1)
Number Date Country
Parent 09/561672 May 2000 US
Child 10/304599 US