Conveyor for bar or pipe

A conveyor system for transporting a work piece from a beginning point to an end point in a longitudinal direction with at least one process step applied in between to such work piece is provided according to the invention. The work piece is propelled in the longitudinal direction over a combination of grooved rollers and conveyor belt units in series. Grooved guide means with, e.g., V, U, or square shapes that are machined into the surface of the rollers prevent the work piece from moving laterally as it is transported in the longitudinal direction, and maintain precise spacing between a plurality of work piece strands undergoing simultaneous transport by the conveyor system. The conveyor belt unit located between the grooved rollers inhibits rotation of the work piece as it is transported in the longitudinal direction. This conveyor system is good for treating the entire exterior surface area of the work piece in a uniform manner, such as coating the surface of rebar, dowel bar, hollow tube, or pipe.

FIELD OF THE INVENTION

This invention relates to an apparatus for conveying a work piece like bar or pipe between stations of a finishing process in a longitudinally aligned, laterally spaced, and non-rotational manner, and a process for finishing such work piece.

BACKGROUND OF THE INVENTION

Principal end products of the steel making industry include bars, including rebar and dowel bar, and extruded tubing including pipe. Iron ore is fed into a huge blast furnace operated at a very high temperature to which is added coke or coal as a reducing agent to remove oxygen from the iron ore. The resulting molten iron is then added to scrap steel that has been heated in a separate furnace, and pure oxygen is blown into the mixture, whereby the oxygen reacts with iron and impurities in the charge to produce the heat necessary to refine the charge into steel. This molten steel may be poured through a mold, cooled and rolled into blooms, billets, and slabs, which can then be hot rolled by means of the grooved rolls of a bar mill to produce steel bars. Alternatively, the heated steel may be forced through a die to form seamless steel tubing and pipe.

Such solid bar may have grooves formed on its exterior surface to produce reinforced bar (“rebar”), which is widely used within the construction industry to reinforce poured concrete against the effects of environmental stress. Solid bar with a smooth exterior surface is called “dowel bar”, and is used for highway construction, primarily as a support piece in concrete (for example, as a component of a dowel bar basket assembly. Hollow metal tubing or pipe is used extensively within the utility industry to transmit oil, gas, and water.

Rebar set in concrete can easily corrode over time, which will reduce its effectiveness in reinforcing the concrete. Likewise, piping laid in the ground can corrode over time due to groundwater and acidic materials contained in the soil. Therefore, it is important to render such rebar and piping corrosion-resistant through the application of a protective surface coating. While steel is commonly hot-dip galvanized with molten zinc for heating ducts and storage tanks, or electroplated with chromium for the manufacture of cans and other containers, rebar and piping manufacturers have gravitated towards the use of liquid or powder coatings that may be sprayed onto the rebar or pipe as it travels at high speeds over conveyor lines within the manufacturing plant.

Flat conveyor belts have been used for a long time by the manufacturing industry to convey products between different work stations within the manufacturing process. Similarly, idle wheels can be used on gravity-type conveyors to support the products as they move along the conveyor line. However, products or boxes can easily fall off a conveyor belt or series of roller wheels, so lateral edges or guide rings are commonly applied to the edges of such conveyor lines to prevent undue lateral movement of the load during transport which could otherwise require the conveyor line to be stopped to retrieve the fallen load. See, e.g., U.S. Pat. No. 4,448,296 issued to Tabler.

The circular cross section of rebar or pipe, however, permits such products freely to roll laterally while traveling along a conveyor belt or gravity-type conveyor. Such uncontrolled lateral movement can lead to the strands of rebar or pipe becoming tangled or jammed on the conveyor line. Therefore, conveyor lines have been equipped with rollers having V-shaped or U-shaped grooves for restraining a rebar or pipe strand against lateral movement while it is transported longitudinally over the roller. See, e.g., U.S. Pat. No. 3,063,533 issued to Cook; U.S. Pat. No. 3,964,435 issued to Horn et al.; and U.S. Pat. No. 2,715,958 issued to Lindstrom et al. Such devices typically employ a motorized chain and sprocket assembly for providing the necessary propulsive force that transports the rebar or pipe longitudinally over the conveyor line.

Depending upon the manufacturing step that is being undertaken, it can be important to properly orient loads on a conveyor line so that they are evenly spaced across the width of the conveyor. For example, U.S. Pat. No. 4,166,526 issued to Wykes et al. uses first and second divider discs with guide faces to pre-separate metal bars undergoing transport prior to their passage over a magnetic roller that laterally spaces the bars with uniform spaces between each bar. Similarly, U.S. Pat. No. 3,071,236 issued to Hahn et al. employs V-belts on a conveyor line to place crackers in aligned orientation across the width of the conveyor line.

Once pipe has been laterally aligned and transported along the length of a conveyor line with V-shaped rollers, a throat plate can be employed to stop the movement of a pipe strand until the previous pipe strand has passed to avoid collisions. See U.S. Pat. No. 2,597,941 issued to Long. U.S. Pat. No. 2,169,624 issued to Weiss et al. discloses the use of idler rollers made of rubber for providing a shock resistant and non-abrasive means for transporting material over a conveyor line.

Other known pipe conveyors include mechanisms for transporting the pipe laterally from one conveyor line to another conveyor line or to a run-off table. See, e.g., U.S. Pat. No. 4,593,807 issued to Cattaneo et al.; U.S. Pat. No. 2,873,840 issued to Kerr et al.; and U.S. Pat. No. 1,021,582 issued to Daniels et al.

While such devices previously known within the industry may be capable of aligning rebar or pipe across the width of a conveyor line for evenly spaced longitudinal transport along the line until they are moved to another line or receiving station, the exterior grooves of rebar often interact with the V-shaped grooves of the conveyor line feed rollers to cause the rebar to rotate during transport. Likewise, vibration induced upon dowel bar or pipe by such V-shaped grooves can cause such dowel bar or pipe to rotate. Were such bar or pipe merely being transported by the conveyor line between work stations or during a quenching operation, this rotation would not be problematic. However, during a surface coating process or an abrasion cleaning process prior to such coating, the entire exterior surface of the rebar or pipe must be accessible to the abrasion cleaning medium and coating product, or else the rebar or pipe surface will be unevenly coated. Rotation of the rebar or pipe during transport can interfere with this continuous abrasion cleaning and coating process.

Therefore, it would be very advantageous to provide a continuous means for transporting multiple strands of rebar or pipe along a conveyor line with controlled lateral spacing between the rebar or pipe strands and without rotation so that all of their exterior surface area may be accessible during the abrasion cleaning and coating processes. Moreover, the conveyor line downstream of the coating process must be designed to prevent chipping of the protective coating from the rebar or pipe after it has been applied.

SUMMARY OF THE INVENTION

A conveyor system for transporting a work piece from a beginning point to an end point in a longitudinal direction with at least one process step applied in between to such work piece is provided according to the invention. A support frame secures a combination of grooved rollers and conveyor belt units in series over which the work piece is propelled in the longitudinal direction. Grooved guide means with, e.g., V, U, or square shapes that are machined into the surface of the rollers prevent the work piece from moving laterally as it is transported in the longitudinal direction, and maintain precise spacing between a plurality of work piece strands undergoing simultaneous transport by the conveyor system. The conveyor belt unit located between the grooved rollers inhibits rotation of the work piece as it is transported in the longitudinal direction. Such work piece can include without limitation rebar, dowel bar, hollow tube, and pipe. The process step applied to the work piece undergoing transport longitudinally with controlled lateral and non-rotational spacing by the conveyor system of this invention can include without limitation cleaning, painting, varnishing, coating, or other types of surface treatment where the entire exterior surface area of the work piece should be treated in a uniform manner.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A process for the continuous transport of multiple strands of pipe or rebar with controlled lateral spacing in a longitudinal direction along a conveyor line without rotation is provided by the invention. Such invention may take the form of feed rollers having V-shaped grooves for controlling the lateral spacing of the rebar or pipe during longitudinal transport over the conveyor line interspersed with sections of flat conveyor belts for arresting the rotational force applied to the rebar or pipe by the feed rollers. This invention also provides an apparatus for transporting the rebar or pipe with controlled lateral spacing without rotation.

For purposes of the present invention, “work piece” means rebar, dowel bar, hollow tube, pipe, or any other product transported along a conveyor line where the surface area of such work piece must be maintained in place against lateral or rotational movement while the work piece is transported in a longitudinal direction to enhance a process step. The cross section of such work pieces need not be round, but may adopt other shapes like shapes that are, e.g., square, rectangular, hexagonal, or octagonal.

As used within this application, “process step” means any automatic treatment of a work piece as part of a manufacturing process where it is important or desirable to treat the entire surface area of the work piece in a uniform manner. Cleaning, painting, varnishing, coating, or other types of metal treatment represent illustrative examples of such a process step.

In the context of the present invention, “rebar” means any solid steel bar with exterior ribbing or other abrasive surface areas that is used to reinforce concrete structures like roadways, highways, retaining walls, and building walls. Rebar typically has a round cross-section with a diameter between 3/8 inches and 1 inch or more, and its standard length is 60 feet.

For purposes of this invention, “dowel bar” means any solid bar having a smooth exterior surface. Dowel bar is manufactured with a variety of cross-sectional shapes, including circular, square, rectangular, hexagonal, and octagonal shapes.

In the context of the presented invention, “pipe” or “tubing” means any hollow elongated cylinder used to contain a liquid or pressurized gas substance during transport. Such pipes or tubes may have a diameter between ½ inch and 96 inches, depending upon the end-use application, and often are manufactured in 40-foot lengths.

As used within this application, “coating” or “coated” means any protective or decorative surface finish applied to a work piece by means of powder spray or liquid spray. Such powder sprayed compounds include fusion bond epoxy resins, as well as acrylic, nylon, phenolic, polyethylene, polyester, and vinyl resins. Such liquid spray compounds include paint, lacquer, varnish, abrasive-resistant coatings, and galvanizing products.

FIG. 1shows the overall process of the present invention in which a work piece is provided with a spray powder coating to form a protective exterior finish. Work pieces10are moved by conventional means from a storage facility to entry racks20where they are sorted into, e.g., eight strands lined up in parallel over a loading mechanism for the entry conveyor22. Depending upon the size and weight of the work pieces, such conventional means for introducing the work pieces10to the entry rack20can include human lifting, a crane, fork lift, gravity-type conveyor, reciprocating mechanical lift arm, etc.

Upon departure from the entry racks20, entry section22of conveyor line25will transport the work pieces10to blast machine30, where the exterior surface of the work pieces10are cleaned by means of grit particles thrown at the work pieces at high velocity. In the case of rebar, this might constitute steel grit particles for cleaning surface rust and mill scale off the rebar.

Next, the cleaned work pieces10are conveyed longitudinally by means of coating conveyor line section24to induction coil heating station40which uses electric current to heat the surface of each work piece. The work pieces10are then almost immediately passed through spray booth50where a powder coating is sprayed onto the work pieces using electrostatic guns that emit a mixture of powder and compressed air.

Upon exit from the spray booth, the work piece strands10are conveyed longitudinally by wet roller section26of conveyor line25to a submersible quench tank60. The rollers of wet roller section26are kept wet with water to eliminate any tracking of the powder coating onto the conveyor components. During the time period that the work pieces are passing through this section of the conveyor line25, the powder coating will flow and gel across the exterior surface of the work pieces10to provide an even protective coating in terms of surface coverage and thickness. Quench tank60is filled with cold water, and is used to rapidly reduce the temperature of the work pieces10as they continue traveling down the conveyor line.

After completely exiting the quench tank60, and passing through an in-line holiday (defect) detector, the work pieces10are lifted off of the coating conveyor25by conventional means, and placed directly onto the exit rack chain conveyor70.

The coating conveyor line25and associated process will now be discussed in greater detail within the context of providing a protective coating to rebar, although it should be understood that this invention is not limited to rebar or applying powder coatings to such rebar. Rather a variety of different process steps can be applied to a multitude of different work pieces using the improved conveyor line of the present invention.

FIG. 2shows coating conveyor line25in greater detail with particular emphasis placed upon the composition of entry section22, coating section24, wet roller section26, and exit section28. Bundles of bare steel rebar are taken out of the storage racks by means of an overhead crane and positioned onto entry racks20. Here, the bundles are broken open and then sorted so that eight strands of bar are lined up in parallel over the loading mechanism for entry section22of coating conveyor line25. The loader transfers the eight strands of rebar onto entry section22. It should be understood that the number of rows of rebar traveling longitudinally down coating conveyor line25may be a number other than eight. While eight is a convenient number for smaller rebar of 3/8 inches or 4/8 inches diameter, larger rebar of 1¼ inch diameter may more effectively be placed in four rows on the conveyor line25. It is important that enough space exist between the moving strands of rebar to permit effective abrasion clearing and spray coating of the rebar surfaces as discussed more fully herein.

Entry section22consists of a series of flat rollers80, grooved rollers82, and flat conveyor belts86, as shown inFIG. 2.FIGS. 3-5illustrate the framework88for entry section22, which consists of a series of seven-foot-long sections. Four-inch channel posts90extend vertically from the floor, and are bolted thereto by means of brackets92. They support on their top surface cross rails93, and side rails94, which are L-shaped and 2 inches along each side. Lateral bracing96, longitudinal bracing98, and diagonal cross bracing100provide needed support to the framework, and bear the downward and outward forces applied by the weight of the rollers, conveyor belts, and traveling rebar. The resulting framework88provides an open top surface that is approximately 21½ inches wide (25½ inches between the exterior edges of side rails94), and approximately 38 inches above the floor for ergonomic convenience.

Mounted on top of side rails94are three flat rollers80, eight grooved rollers82, and fifteen flat conveyor belt sections84that collectively comprise entry section22. While this number and arrangement of rollers and conveyor belts has been found to work effectively for ordering, spacing, and conveying 60-foot long lengths of rebar to abrasive blast machine30, the number and arrangement of these components could be readily modified by a person skilled in the art for shorter lengths of rebar or other types of work pieces.

FIGS. 6 and 7illustrate the design of flat rollers80. Each flat roller comprises a steel roller cylinder102that is approximately 20 inches in length and 4½ inches in outside diameter. Passing through the length of roller cylinder102is a 1-7/16 inch shaft104that extends approximately 3 inches past one end of the roller to form a solid end106and 5½ inches past the other end of the roller to form keyed end108. Guide rings110are mounted on each end of roller cylinder102and have a larger diameter than roller102sufficient to trap any rebar that would otherwise move laterally and fall off the roller to the floor, while traveling in the longitudinal direction.

Flat roller80is securely mounted to side rails94by means of a pillow block bearing110that engages solid end106of shaft104and a bearing and sprocket assembly114that engages keyed end108of shaft104. The purpose of flat rollers80is to provide forward longitudinal force to the rebar strands at the beginning stage of entry section22of conveyor line25when precise lateral spacing of the individual rebar strands is less important than later along the conveyor line.

FIGS. 8 and 9show grooved rollers82. Like flat roller assembly80, grooved roller assembly82comprises a roller120, shaft122having solid end124and keyed end126. Also like flat roller assembly80, grooved roller assembly82is mounted to top rails94by means of pillow block bearings112and bearing and sprocket assemblies114. However, the otherwise cylindrical surface of roller120has a series of, e.g., eight V-grooves128machined into its surface to form V-grooved channels130that extend laterally across roller120in the longitudinal direction of the traveling rebar. So that V-grooved rollers may accommodate a variety of different diameters of rebar, such V-grooved channels130are approximately six inches across their top edge132, approximately 4½ inches across their bottom edge134, and approximately ¾ inches in depth136. Roller120and V-grooves128preferably are made from nylon since it is easier to machine nylon, although steel may be used. The purpose of grooved rollers82is to maintain precise lateral alignment of the rebar strands as they are conveyed along entry section22of conveyor line25.

Flat conveyor belts84are shown inFIGS. 10 and 11.FIG. 11also shows two sections of flat conveyor belt84in combination with one grooved roller82. Each flat conveyor belt84comprises a belt140stretched between an idle roller142and a drive roller144. The belt140is preferably made from butyl rubber with four plies rated at 200 lb./sq. in capacity. The temperature rating for this material is 250° F. Rollers140and144look very similar to the construction of flat rollers80, having cylindrical roller146and shaft148. However, the shaft148ends in two solid ends150for mounting to top rails94by means of pillow block bearings112. The shaft148of driver roller144, on the other hand, ends in solid end150and keyed end152so that it can be mounted to top rails94by means of pillow block bearing112and sprocket assembly114, respectively. Belt140is approximately 20 inches wide, and has a center-to-center length of approximately 19½ inches.

The purpose of flat conveyor belt84is to dampen the rotation of a rebar strand as it comes off of a grooved roller82. A series of chain drives160are operatively engaged between the sprockets ends of a flat roller80, grooved roller82, or driver roller144of a flat conveyor belt84to move these rollers and belts in a synchronized fashion powered by a motor (not shown), so that eight strands of rebar can be moved along entry section22to abrasive blast machine30in precisely laterally spaced alignment without rotation of the individual rebars. It has been found that spacing between the flat conveyor belts84and grooved rollers82of approximately 14½ inches achieves this objective, which also provides sufficient longitudinal support of smaller diameter rebars that might otherwise be subject to bending or drooping.

Abrasive blast machine30comprises a cabinet approximately four feet long without any rollers or conveyor belts positioned therein. A rotating series of paddles within the booth throw steel grit particles at high velocity at the rebar strands whose exterior surface is accessible from all directions. The steel grit particles are at least 95% iron, and may be sourced from Ervin Industries of Ann Arbor, Mich. or Wheelabrator Abrasives of Bedford, Va. Such abrasive blast machines are known in the art, and the components for the machine of the present invention were sourced from Midwest Pipe Coating, Inc. of Schererville, Ind.; Blastec, Inc. of Alpharetta, Ga., and Industrial Associates, Inc. of Waukesha, Wisc. It has been found that the four-foot length of abrasive blast machine30provides sufficient residence time for rebar traveling through it at approximately 24-56 feet/minute to achieve thorough cleaning of the surface rust and mill scale from the rebars by means of the steel grit particles.

Upon exit from the abrasive blast machine30, the rebar strands are conveyed to induction coil heating station40by means of coating section24of conveyor line25. As shown inFIG. 2, this portion of coating section comprises five grooved rollers82and three flat belt conveyors84. Induction coil heating station24preferably consists of two separate stations in series with a grooved roller82positioned in between. Each such station comprises an induction coil which introduces electric current to the rebar strands passing thereunder in order to heat the surface of each rebar to approximately 450° F. Such induction coils are known in the art, and the ones used in the present invention were manufactured by Pillar Industries of Brookfield, Wisc. The distance across each induction heating coil station is approximately two feet.

Upon leaving the induction coil heating stations40, the rebar strands are conveyed by means of two more grooved rollers82to spray booth50. This coating chamber comprises a booth approximately four feet in length that was purchased from G&R Electro-Powder Corp. of Indianapolis, Ind. Electrostatic spray guns sourced from Nordson Corp. of Amherst, Ohio are mounted within the booth for emitting a cloud of powder coating at the rebar strands as they pass therethrough. The absence of rollers or flat conveyor belts inside the booth permit this powder coating to be electrostatically attracted to the surface across the entire diameter of each rebar in transit whereupon it coats the rebar surface. Overspray of the powder is continuously reclaimed from the coating booth for reuse in the coating process.

For purposes of rebar, a fusion bond epoxy powder is preferably used. Two such products are SCOTCHKOTE® 413 spray-grade fusion-bonded epoxy coating (70-90% 4,4′-isopropylidenediphenol-epichlorohydrin polymer) manufactured by 3M Company of St. Paul, Minn., and GREENBAR® 720A009 powder paint (90-95% of a “proprietary resin”) manufactured by Valspar Corporation of Minneapolis, Minn. For purposes of coating pipe, 3M's SCOTCHKOTE® 6233 fusion-bonded epoxy coating (55-75% di(4-hydroxyphenol)isopropylidene-di(4-hydroyphenol)isopropylidene copolymer) or the GREENBAR 720A009 material may be used. These powders are applied to the rebar or pipe by the electrostatic guns at a rate of approximately one pound per minute (per gun) in order to achieve a uniform coating thickness of approximately 5-60 mils (i.e., 0.005-0.60 inches). While liquid coatings may alternatively be used within the intended scope of this invention, powder coatings tend to cure faster than liquid coatings. They also permit the recycling of overspray, which can improve processing economics. Therefore, powder coatings applied electrostatically are preferred for purposes of coating rebar and pipe.

The combination of grooved rollers82and flat conveyor belts84of the coating section24shown inFIG. 2cooperate to convey the rebar strands to and through coating chamber50in precisely laterally spaced alignment without the rotation that would otherwise be imparted by the grooved rollers, alone, so that uniform coverage and thickness of protective coating can be introduced to the rebar surfaces as they pass through the coating chamber. The construction of the guide rollers82and flat conveyor belts84of coating section24are the same as those of entry section22described above, and will not be repeated again.

The rebar strands leave the coating chamber50by means of wet roller section26whereupon they are conveyed to quench tank60. As shown inFIG. 2, wet roller section26of conveyor line25comprises a series of grooved rollers82and flat conveyor belts84. The flat conveyor belts are used in the first half of wet roller section26where it is still important to dampen down any rotational force on the lead portion of the rebar strands, so that rotation that would otherwise affect the rebar strands does not interfere with the uniform coating of the latter portion of the strands as they pass through the coating chamber50. This is no longer an issue in the latter part of wet roller section26, or quench tank60for that matter, so grooved rollers alone are used in those portions of conveyor line25.

The flat conveyor belts and grooved rollers in the wet roller section26are kept wet in order to eliminate any tracking of the coating powder onto the conveyor components. This section provides a sufficient period of time as the rebar strands pass therethrough for the coating to flow and gel evenly across the rebar to further ensure uniform coverage and thickness, as well as to start to cure. For example, the SCOTCHKOTE 413 powder is rated for a gel time of 4-5 seconds with a time-to-quench of 27 seconds. It has been found that a wet roller section approximately 30 feet in length accomplishes this purpose.

The rebar strands then are conveyed to quench tank60whereupon they are completely immersed in cooling water as they travel down the coating conveyor line25. This quench tank60is approximately 26 feet long, and serves to reduce the surface temperature of the rebar strands to approximately 180° F. as they exit the tank.

The rebar strands completely exit the quench tank area and pass through an inline holiday (defect) detector by means of exit section28, which consists primarily of flat rollers80and flat conveyor belts84, since precisely spaced lateral alignment of the rebars is no longer important. The rebar strands are then lifted off of exit section28of coating conveyor line25by means of an exit transfer cart assembly (not shown) of conventional design, and placed directly onto exit rack chain conveyor70. This chain conveyor70moves the rebar strands laterally to the exit bundling pockets, where the individual strands are bound back together in a bundle, and hauled via an overhead crane to the storage racks.

It is important downstream of coating chamber50that the components of wet roller section26, quench tank60, exit section28, and the exit rack chain conveyor not chip or otherwise mar the protective coating that has been applied to the exterior surface of the moving rebar strands. Therefore, the grooved rollers82and flat rollers80which have a steel core, are coated with an ultra-high molecular weight (“UHMW”) plastic material, or could be coated with polyurethane or nylon as a substitute, although UHMW plastic is the preferred coating material. In this manner, the coated rebar strands may be safely conveyed over these rollers without damage to the coatings. For the same reason, the crane lifts the rebar strands with a nylon web sling off of the exit rack chain conveyor to the storage racks. From here, the rebar can be shipped to a customer or further processed.

Table 1 provides illustrative data for the number of strands conveyed and line speed for different sized rebars in accordance with the present invention.

The above specifications, data and drawings provide a complete description of the manufacture and use of the apparatus and process of the invention. Many alternative embodiments of the invention can be made without departing from the spirit and scope of the invention. For example, other work pieces besides rebar can be processed by the apparatus and process of the present invention. Likewise, a processing step other than surface coating may be applied to the work piece by this invention. Moreover, alternate arrangements and combinations of grooved rollers and flat belt conveyors can be used besides that shown inFIG. 2.

Furthermore, other grooved configurations besides V-grooves (e.g., a U-groove or square groove) can be substituted for the grooved rollers that will still retain the work piece in a laterally and rotationally stationary position depending upon the cross-sectional shape of the work piece. For example.FIG. 12shows an alternative grooved roller embodiment 170 of the present invention in which a series of U-shaped grooves172are machined into the roller surface120to form U-shaped channels174that extend laterally across roller120in the longitudinal direction of the traveling rebar. Likewise,FIG. 13illustrates another alternative grooved roller embodiment 180 of the present invention bearing square-shaped grooves182machined into the roller surface to form square-shaped channels184. FinallyFIG. 14depicts yet another alternative embodiment 190 of the grooved roller120in which rectangular-shaped grooves192are machined into the roller surface to form rectangular shaped channels194.

Therefore, the invention resides in the claims hereinafter appended.