WO2000021749A1

WO2000021749A1 - Molded railroad tie and method for making same

Info

Publication number: WO2000021749A1
Application number: PCT/US1999/023846
Authority: WO
Inventors: Daniel D. Phillips; Michael L. Mcguire
Original assignee: Reconstituted Technologies, Inc.
Priority date: 1998-10-15
Filing date: 1999-10-14
Publication date: 2000-04-20
Also published as: AU1112100A

Abstract

A molded railroad tie is provided which utilizes used railroad ties in its construction. The railroad tie includes strands which are produced from used railroad ties. A resin is also included and is blended with the strands to act as a binder to hold the strands together. The strands and the resin mixture is compressed into a mold which is shaped to conform to the shape of existing railroad ties. The mold is then heated to cure the resin to produce a railroad tie made primarily from used railroad ties.

Description

MOLDED RAILROAD TIE AND METHOD FOR MAKING SAME

BACKGROUND OF THE INVENTION The present invention relates to molded wood products made from recycled materials, and more particularly to molded railroad ties made from recycled railroad ties, as well as the method for making such railroad ties.

In a typical railway system, a train is carried on a pair of spaced parallel rails. The rails are in turn carried by a series of railroad ties. The ties are oriented perpendicularly to the rails, and extend outwardly beyond the rails. In the past, ties have been made from timbers, cut to size. The timbers are treated with creosote to increase the resistance to premature weathering. Ties are typically installed on a bed of ballast, which conventionally consists of gravel or crushed rock. The ballast serves to support the ties and rails, and to hold them in position. Each year in the United States alone, upwards of twenty-million railroad ties are replaced. The need for replacement of these ties stems from the high wheelloads, as well as the increased use of railways to transport a variety of goods. This increased use translates into ever-increasing loads, which are carried by the railroad ties.

The need for replacement railroad ties presents two problems. First, the disposal of old railroad ties presents environmental challenges. Because the ties are treated with creosote, the ties must be disposed of in an environmentally friendly matter. The old practice of placing old ties along the railway line, on the ground, is no longer acceptable. The second problem created is based solely upon the need for new ties. In the past, ties have been cut from timber to size. Thus, a great deal of timber is needed each year just to replace the railroad ties that have become worn or that have failed.

Due to these problems, a number of different approaches have been attempted to replace the historical wood railroad ties. For example, the use of concrete or steel railroad ties has been developed and tested. Ties made from laminated wood materials, and ties made from synthetic resins have also been tested. However, these attempts have not lead to any full-scale commercial use. The approaches discussed above involve ties that are more expensive than traditional wooden ties. Further, the above- discussed ties are typically not compatible with existing railway tie anchoring methods, such as spikes, leading to additional cost in use on conventional rail bed. In an attempt to address the above-identified problems, a recycled railroad tie is disclosed in U.S. Patent No. 4,108,377 to Potter et al. Potter discloses the use of recycled railroad ties in the construction of replacement ties. This solves the problem of disposal of the old ties, because they are used in the construction of the new or replacement ties. Potter discloses the use of pulverized railroad ties, along with a pair of reinforcing members, in the construction of a replacement tie. The use of the reinforcing members adds to the strength of the tie, but also increases the cost thereof. The need for the reinforcing member also adds to the complexity of the process used in manufacture of the tie. Therefore, a replacement railroad tie is needed that overcomes the drawbacks and deficiencies of previous engineered ties. Further, a method is needed that can be used to manufacture a replacement railroad tie from old ties that overcomes the drawbacks and deficiencies discussed above.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a replacement railroad tie that is made from old railroad ties that have been removed from service.

It is a further object of this invention to provide a replacement railroad tie that can withstand the loads produced during use in a railway line.

It is yet another object of this invention to provide a replacement railroad tie that uses reclaimed railroad ties and that does not require the use of reinforcing members.

It is still another object of the invention to provide a new process for producing a replacement railroad tie that uses reclaimed railroad ties and that does not require the use of reinforcing members. According to the present invention, the foregoing and other objects are obtained by a molded railroad tie which utilizes used railroad ties in its construction. The railroad tie includes strands which are produced from used railroad ties. A resin is also included and is blended with the strands to act as a binder to assist in holding the strands together. The strands and the resin mixture is compressed into a mold which is shaped to conform to the shape of existing railroad ties. The mold is then heated to cure the resin to produce a railroad tie made from used railroad ties and a resin addition. Additional objects, advantages, and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the accompanying drawings which form a part of the specification and are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views: Fig. la is a partial schematic of the equipment and layout used in constructing a railroad tie according to the invention;

Fig. lb is a partial schematic of the equipment and layout used in constructing a railroad tie according to the invention;

Fig. lc is a partial schematic of the equipment and layout used in constructing a railroad tie according to the invention;

Fig. Id is a partial schematic of the equipment and layout used in constructing a railroad tie according to the invention;

Fig. 2 is a legend showing the orientation of Figs. la-Id relative to one another; Fig. 3 is a perspective view of the mold and hopper used in constructing a railroad tie according to the invention;

Fig. 4a is a partial flow-chart showing the method used to construct a railroad tie according to the invention; and

Fig. 4b is a partial flow-chart showing the method used to construct a railroad tie according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

A schematic equipment layout used in constructing molded railroad ties according to the present invention is shown in Figs. la-Id, which are oriented according to the legend shown in Fig. 2. Initially, used railroad ties are brought into the plant by mobile equipment and are manually sorted into acceptable and unacceptable material by visual inspection. Turning initially to Fig. lc, the acceptable used railroad ties, which provide the material for a main component of the molded railroad ties of the present invention, are placed onto an agitator holding deck 10. Deck 10 is used to transfer the acceptable used railroad ties to an agitator infeed conveyor 12. Agitator infeed conveyor 12 transports the used railroad ties to a deal processor 14. Deal processor 14 is used to remove a majority of the stones and other debris which may be present on the used railroad ties. A suitable commercial model deal processor is the RS425, available from Valon Kone Brunette Ltd., of New Westminster, British Columbia, Canada. The deal processor subjects the old ties to a tumbling and impacting process, thus removing varying percentages of the outer surface of the used ties. The amount of outer surface removed depends upon the condition of the ties and the amount of contamination present. Usually, between five and twenty percent of the outer surface is removed. It is not necessary for the used railroad ties to enter the deal processor in a singular fashion, and therefore the ties do not need to be singulated when transferred from holding deck 10 to infeed conveyor 12. The processed ties leave deal processor 14 on an agitator outfeed conveyor 16. Conveyor 16 transports the processed ties into a tie bunk 18 where the used and partially processed ties are left to be collected and further processed.

The used railroad ties are again visually inspected after they have been passed through deal processor 14, and the rejects are grouped with other unacceptable used railroad ties. The acceptable used and partially processed ties are placed onto a log pond infeed hopper 20 which transports the used railroad ties through a log pond 22. Pond 22 is filled with a liquid, which is preferably water. The log pond helps to remove remaining contaminants, such as sand, that are remaining after deal processor 14, and conditions the wood to enable a more consistent geometry of strand later in the process, as is more fully described below.

The railroad ties leave pond 22 via a jackladder conveyor 24 which singulates the ties as it removes them from pond 22. The partially processed ties drop from the end of jackladder 24 onto an outfeed conveyor 26. As the ties pass along conveyor 26, they pass a visual inspection station 28. Any unacceptable ties are swept off of conveyor 26 into a reject log bunk 30 by a manually controlled reject kicker 32. Any rejected ties are removed from bunk 30 by mobile equipment and are placed with the other unacceptable or rejected ties. The acceptable ties continue along conveyor 26 and are passed through a metal detector 34. Typically, the metal which is detected will be a remaining piece of an old railroad spike. If metal is detected in a railroad tie, the tie is rejected and routed to an end slashing infeed conveyor 36. Conveyor 36 conveys the rejected ties to an end slashing deck 38. Deck 38 is used to remove a portion of each end of the tie. Typically, the railroad spikes are located a specified distance inward from each end of the railroad tie. Therefore, it may be necessary to remove as much as 18 inches from each end of the railroad tie. The removed ends of the railroad tie are routed to a reject log conveyor 40 by end dropout chutes 42. The mid-section of each tie, after slashing deck 38, is dropped onto a log return conveyor 44 and is passed through a metal detector 46, which is similar to detector 34. If metal is detected by detector 46, the mid-section of the tie will be routed via reject chute 48 onto reject log conveyor 40. If no metal is detected by detector 46, the mid- section of the used railroad tie is conveyed to tie return holding deck 50. The acceptable mid-sections of the used ties are stock-piled on deck 50 for return to the process.

If no metal is detected by metal detector 34, the used ties continue along a slasher infeed conveyor 52 which routes the ties to a slasher incline conveyor 54, as best seen in Figs, lc and Id. Conveyor 54 transports the ties to a slasher deck 56, which cuts the ties into an average length of approximately 34 inches. After the ties have been cut to length by slasher deck 56, they are dropped onto one of two slasher outfeed conveyors 58, as best seen in Fig. lb. A flop gate is used to control which of the two conveyors 58 the ties drop onto. Conveyors 58 transport the tie sections to block strander infeed conveyors 60, which in turn transport the tie sections to one of two block stranders 62, as seen in Figs, lb and Id. Block stranders 62 are used to cut the tie section into the strands which are utilized to form the recycled ties of the present invention. Stranders 62 produce strands which are approximately three-quarters of an inch in width, which are between three and six inches in length and which are about twenty thousandths to fifty thousandths of an inch thick.

Material leaving block stranders 62 is discharged onto one of a pair of block strander outfeed conveyors 64. Conveyors 64 transport the strands onto one of two wet bin infeed conveyors 66. The strands exit conveyors 66 and are deposited into a wet bin 70 which is located directly above a strand dryer 72. A suitable wet bin is a live bottom PS&E or Clark type of 5,000 to 10,000 cubic foot capacity. A suitable dryer 72 is that made by M-E-C Company of Neodesha, Kansas. Dryer 72 is equipped with a discharge screw to meter the wet strands into the dryer.

After the strands have been dried to a desired moisture level by dryer 72, they are screened by a screening device 74. A suitable moisture content has been found to be five to ten percent. Stranders 62 not only produce strands, but also produce a certain amount of smaller particles, called fines. Device 74 allows any fines produced to be removed from the primary process. The extracted fines are conveyed using a screw type conveyor 76 to a fines outfeed conveyor 78. Conveyor 78 transports the fines to a fuel bin 80 for use in the energy system of the plant, as is more fully described below. Moreover, device 74 classifies the strand material by size. Smaller strands are separated from larger strands by screening device 74. The smaller strands can then be used for the core of the molded railroad tie, while the larger strands are used on the top and bottom faces of the tie. This classification can result in increased strength properties of the molded railroad tie.

The separated strands are transported by a screen outfeed conveyor 82 to a dry bin infeed conveyor 84. Conveyor 84 maintains the separation of the strands and deposits the strands into one the compartments of a dry bin 86, where the strands are stored and later metered into a blending process. Dry bin 86 is equipped with a discharge screw conveyor, which meters the desired size strands into a blender 88 which is located below the dry bin. In blender 88, the strands are blended with a resin in a blending drum. Typically, about 6-10% by weight of resin is used, with the remainder being the processed strands. A preferred resin is methylene diphenyl diisocyanate, or MDI. As best seen in Figs. Id and lb, after the strands have been blended with the proper amount of resin, they are transported to a forming line infeed conveyor 90 that takes the strands from the blender and carries them to a forming line distribution conveyor 92. Conveyor 92 transports the strands to the forming line distribution area 94 where the strands are divided between three forming head metering bins 96. At the bins 96, the strands are placed in molds 98, as best seen in Fig. 3. Each mold is appropriately sized to fabricate a standard size railroad tie. A typical tie is approximately 7 inches tall, 9 inches wide and 9 feet long. Placed on top of each mold is a hopper 100. Hopper 100 allows the appropriate amount of strand material to be placed above the mold for compression into a railroad tie. In a typical application, approximately 45 inches of strand and resin material is compressed into a 7 inch tall recycled tie. A disc screen or bar screen is used to orient the strands within the mold and hopper, so that the strands are aligned with the longitudinal axis of the mold. This is accomplished by selecting the interface opening in the disc screen to control the flow of material through the disc.

After the appropriate amount of material has been placed in mold 98 and hopper 100, the assembly is transported to one of two presses 102. Presses 102 exert a compression force upon a lid 104 which has been placed on top of the strand material. The strand and resin material is compressed by press 102 until lid 104 resides generally on top of mold 98. Presses 102 generally exert forces of between 2800-3500 pounds per square inch. The resulting recycled tie has a density of about 60 pounds per cubic foot. Following the compression of the material, the lid 104 is secured to mold 98 and the mold 98 and lid 104 assembly is transported to one of two ovens 106, as best seen in Figs, lb and la.

Ovens 106 are used to cure the resin and strand material which is controlled by temperature and time. A temperature of between 500-550° F is suitable as a front end head temperature, which may be reduced to lower than 410° F as the assembly progresses through oven 106. Using these temperatures, a cook time of between 3 and 4 hours is suitable. Suitable ovens are available from a number of suppliers, one being Despatch Industries of Minneapolis, Minnesota. Following ovens 106 the mold and the lid assembly 98 and 104 is passed through one of a pair of in-line coolers 108 which cools the mold 98 and lid 104. A cooling time of about 1 hour has been found to be sufficient. After the mold 98 and lid 104 have been cooled, lid 104 is removed, and a recycled railroad tie 105, as shown in Fig. 3, is extracted from mold 98. The railroad ties 105 are then ready for stacking and are conveyed via exit conveyor 114. Mold 98 is then returned via a mold return conveyor 110 which includes a mold cleaning station 112.

Turning back to Figs, lc and Id, the unacceptable ties that were originally rejected after a first visual inspection, and which were rejected after inspection station 28 into reject bunk 30 are transported by mobile equipment to a reject tie infeed deck 116. Deck 116 singulates the ties and transfers the ties, one by one, to reject tie conveyor 40. Conveyor 40 takes all unacceptable material and delivers it to a hog infeed conveyor 118 which transports the material to a hog 120. Hog infeed conveyor 118 is equipped with a by-pass bunker 122 which allows the hog to be by-passed if necessary.

Hog 120 grinds or pulverizes all of the unacceptable material. The ground material is then dropped onto a hog outfeed conveyor 124 which conveys the material past a metal detector 126. If metal is present, the metal-laden material is diverted into a fuel bin by-pass chute, where it falls into a bunker 128. If there is no metal present, the pulverized material is transferred to a fuel bin infeed conveyor 130 which transports the material to fuel bin 80. Fuel bin 80 is used as a storage facility for the pulverized material. Fuel bin 80 is equipped with a discharge system which allows the pulverized material to be metered for outfeed. The discharge system releases the pulverized material to a fuel bin outfeed conveyor 134 which in turn transfers the pulverized material to an energy system infeed conveyor 136. Conveyor 136 provides the pulverized material to an energy system 138, shown in Figs, la and lc, such as a furnace, where the pulverized material is used as a fuel. As shown in Figs.4a and 4b, in the method of the present invention, used railroad ties are first subjected to an inspection operation 140. If the tie is unacceptable, it is routed to a reject station 142. If the tie is acceptable, it is placed through an agitation operation 144. Following the agitation operation, the ties are again placed through an inspection operation 146. If the ties are unacceptable, they are again routed to reject station 142. If the ties are acceptable, they are placed through a soaking operation 148 after which they are again visually inspected as at 150. If the ties are unacceptable at visual inspection station 150, they are routed to reject station 142. However, if the ties are acceptable, they are passed through a metal detector as at 152. If metal is found at the metal detection operation 152, the ends of the ties are then removed, as at 154. The removed ends are then routed to reject station 142. The remaining portion of the tie is then passed through a metal detector as shown at 156. If metal is present, the remainder of the tie is routed to reject station 142. If no metal is found in operation 156, the remaining ties are routed to a slasher deck as shown at 158 where the ties are cut to length as shown at 160. After the ties are cut to length, they are subjected to a stranding operation

162 followed by a drying operation 164. The strands produced by the stranding operation are about three quarters of an inch wide, about twenty thousandths to fifty thousandths of an inch thick, and between three and six inches in length. After the ties have been stranded and dried, they are subjected to a fine removal operation 166. All fines removed from the material are routed to a fuel bin as shown at 168. The remaining material not removed, is classified by size and is subjected to a blending operation as shown at 170, where the strands are blended with a resin. The strands are preferably blended with MDI resin such that the mixture is about between 6-10% by weight MDI resin, with the balance being the strand material. The blended strands are then metered into a mold and hopper assembly as shown at 172. Included in this metering process is an orienting process to orient the strands to align with the longitudinal axis of the mold and hopper. After the metering operation 172, the strands are compressed in the mold as at 174, and a lid is placed on top of the compressed material. After compressing the material at 174, the hopper is removed at 176 and the mold is thereafter subjected to a heating operation 178 which is followed by a cooling operation 180. After cooling operation 180, the new recycled tie is removed from the mold at 182. Following the above method results in a recycled railroad tie of superior strength using existing railroad ties as a primary component.

All of the material routed to reject station 142 is thereafter routed to a hog grinder as at 184. After the material has been pulverized in the hog grinder, it is again subjected to a metal detection operation 186. If metal is detected, the material is discarded as at 188. If no metal is detected, the pulverized material is transferred, along with the fines, to a fuel bin as at 190. Material in the fuel bin is then transferred as fuel to the energy system as needed as shown at 192.

From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure. It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Claims

Having thus described the invention, what is claimed is:

1. A molded railroad tie utilizing used railroad ties, comprising: strands produced from used railroad ties; and a resin blended into said strands, said resin acting as a binder to hold said strands together; wherein said strands and said resin are subjected to compression within a mold, shaped to conform to a railroad tie, and wherein said mold is heated to cure said resin to produce a railroad tie of sufficient strength made primarily from used railroad ties.

2. The molded railroad tie of claim 1, wherein said strands are generally between three and six inches in length.

3. The molded railroad tie of claim 2, wherein said strands are about three quarters of an inch in width.

4. The molded railroad tie of claim 3, wherein said strands are between 0.020 inches and 0.050 inches thick.

5. The molded railroad tie of claim 4, wherein said strands are oriented longitudinally along a longitudinal axis of the railroad tie in a plurality of layers, and wherein longer strands are placed in a top and a bottom layer and shorter strands are placed in a central layer.

6. The molded railroad tie of claim 1, wherein saidresin is methylene diphenyl diisocyanate.

7. The molded railroad tie of claim 6, wherein said resin is present at between six and ten percent by weight, with the remainder of the weight being provided by the strands.

8. A method of making a molded railroad tie using used railroad ties, said method comprising the steps of: stranding the used railroad ties into strands of a desired geometry; blending the strands with a resin; placing the strand and resin mixture into a mold; compressing the strand and resin mixture within said mold; heating said compressed strand and resin mixture within said mold; and removing the compressed strand and resin mixture from said mold; wherein said strand and resin mixture after compression and heating constitutes a railroad tie suitable for use in a railway line.

9. The method tie of claim 7, wherein said strands are generally between three and six inches in length.

10. The method of claim 8, wherein said strands are about three quarters of an inch in width.

11. The method of claim 9, wherein said resin is methylene diphenyl diisocyanate.

12. The method of claim 10, further comprising soaking said used railroad ties prior to stranding said ties.

13. The method of claim 11, further comprising drying said strands before blending said strands with said resin.

14. The method of claim 12 wherein said resin comprises between six and ten percent by weight of said molded railroad tie.

15. The method of claim 13, further comprising cooling said mold prior to removing the strand and resin tie.

16. The method of claim 7, further comprising detecting for metal in said used railroad ties prior to said stranding, and removing said ties containing any metal prior to said stranding.

17. The method of claim 15,furthercomprisingpulverizing anypieces not used in said stranding and using the pulverized material in an energy system for a facility.

18. The method of claim 8, further comprising orienting said strands within said mold so that the longitudinal axis of said strands is aligned with the longitudinal axis of said mold.