Apparatus and method for detaching cables from a center beam railcar

Information

  • Patent Grant
  • 6283700
  • Patent Number
    6,283,700
  • Date Filed
    Wednesday, June 21, 2000
    24 years ago
  • Date Issued
    Tuesday, September 4, 2001
    23 years ago
Abstract
A tool for removing tie down cables from a center beam rail car loaded with cargo, the apparatus comprising a support beam having a width selected to be greater than the span between a number of tie down cables on the center beam rail car. A plurality of hook-shaped cable claws are rigidly attached in a spaced apart, downwardly extending manner to the support beam. At least one lift sleeve rigidly attached to the support beam and having a receiving end for attaching to an external lift mechanism.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates, in general, to railroad freight cars, and, more particularly, to an apparatus, system and method for unloading railcars having a center beam structure extending along the length of the car body.




2. Relevant Background




Center beam railcars have been used for a number of years to carry cargo such as lumber, building materials, and generally any cargo that can be packaged in packages of substantially uniform size and shape. Center beam railcars offer advantages of lower size and weight, and therefore can carry greater cargo weight. This feature results in greater efficiency in transport, greater fuel efficiency as compared to conventional boxcar designs.




Generally, a center beam railcar comprises a flatbed-like railcar usually with bulkheads on both front and back ends of the car. The center beam railcar has substantially no sidewalls or roof structure. A center beam or partition structure runs along the length of the car extending upwardly from the deck. The center beam structure provides for the static and dynamic loads associated with the cargo during transport.




Center beam railcars have an integral cable-stayed load tie-down system. At an upper portion of the center beam a mounting structure is formed or attached that includes a plurality of keyhole slots for attaching cables, straps, or other means of securing the load. To unload a center beam railcar a person must climb atop the railcar to release the cable tie-down system from the keyhole slots. This operation presents a significant safety hazard as personnel can easily fall from the top of the railcar. This is particularly true when the operation must be performed in rain, snow, or other adverse conditions. Another disadvantage is that the cables and components of the tie down system can easily fall from the car presenting significant risk of injury to people positioned below the car.




This safety problem has been addressed with stopgap measures awaiting a more permanent solution. For example, the task can be performed by an operator protected from falling by a cage suspended by a forklift. This solution makes the task of releasing the cable-tie more cumbersome and time consuming. Moreover, two operators are required for the task rather than one operator as intended. A need exists for a method of releasing the cable tie system that improves safety while allowing rail yard operators to efficiently unload center beam type railcars.




SUMMARY OF THE INVENTION




Briefly stated, the present invention involves a method, apparatus, and system for uncabling a center beam flatcar. In transport, a load is retained on the railcar using a tie down assembly attached to key holes of an upper rail of the flatcar. In accordance with the present invention a cable removing apparatus is operated by loosening cable tie downs to create cable slack, then attaching the cable removing apparatus in accordance with the present invention to a lift mechanism having a plurality of cable claws located distally from the lift mechanism. The cable claws are positioned so that tip ends of the cable claws are adjacent to the loosened cables and clear of a load carried in the railcar. The cable claws are shifted sideways in the direction of the cables such that the tip ends enter a loop created by the cable slack. Using the lift mechanism, the cable claws are raised to engage the cables and lift the cable claws above the upper rail of the center beam. The cable claws are moved towards the upper rail of the center beam flatcar until all of the cables engaged by one of the cable claws are released from the keyholes in the upper rail. The cable claws are moved away from the upper rail until the cables are pulled free of the railcar and fall to the ground.




A cable removing apparatus in accordance with the present invention includes a plurality of hook shaped cable claws that are rigidly coupled in a spaced apart, aligned fashion to a support beam. The cable claws are spaced from each other by a spacing substantially similar to cable-to-cable spacing in center beam flatcars. The support beam is coupled to one or more lift sleeves having a receiving end for removably attaching to an external lift mechanism. Optionally, a safety gate is attached by hinges to the cable removing apparatus near the receiving end of the lift sleeves to protect a lift operator from falling cables during operation.




A cable removing system in accordance with the present invention is designed to enable a single operator using a lift mechanism such as a forklift to remove cable ties securing a load to a center beam flatcar. The system in accordance with the present invention includes a cable removing mechanism that removeably attaches to a lift mechanism such as a forklift or overhead crane. The cable removing apparatus includes a plurality of spaced apart aligned cable hooks positioned at a first end and a lift mechanism receiver located at a second end. The cable hooks extend downwardly a sufficient distance to engage a loosened cable tie down from above the load.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

shows an overview of the system and method in accordance with the present invention;





FIG. 2

shows a side view of an exemplary center beam flatcar;





FIG. 3

shows a top-down view of an upper rail of the center beam flatcar shown in

FIG. 1

;





FIG. 4

shows a cross-section view through the middle of a loaded center beam flatcar;





FIG. 5

illustrates a top-down view of an exemplary configuration of the present invention;





FIG. 6

shows a front-to-back view of an embodiment of the present invention;





FIG. 7

shows a side view of the embodiment shown in

FIG. 6

;




FIG.


8


and

FIG. 9

illustrate perspective views of a cable removing apparatus in accordance with the present invention;





FIG. 10

illustrates a top portion of a rail car in which the present invention is operable;





FIG. 11

illustrates a top-down view of a portion of

FIG. 10

; and




FIG.


12


-

FIG. 19

illustrate various stages in a method in accordance with the present invention.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS




The present invention addresses the deficiencies of the prior art by providing a system that enables a single freight yard operator to safely and efficiently disengage the cable tie downs on a center beam flatcar.

FIG. 1

illustrates an overview of the present invention in which an operator (not shown) using fork lift


601


and the cable removing mechanism


401


in accordance with the present invention can detach cables


113


from a loaded center-beam freight car


101


.




An exemplary center beam car


101


for use in the present invention is shown in FIG.


1


and in side view in

FIG. 2

, although the present invention is readily adaptable to a variety of freight car designs. Car


101


includes a car body


102


having a pair of opposite ends


103


. Car body


102


is constructed, for example, of structural steel tubing and sheet steel and carried on a pair of conventional wheeled trucks


104


. A coupler


106


is typically provided on each end


103


. In a typical application car


101


would include a variety of accessories such as ladders, brake wheels, supports, and the like that are not shown to ease understanding of the present invention.




Car


101


includes a longitudinally extending center sill


107


(best seen in

FIG. 4

) and a pair of side sills


108


extending longitudinally of car body


102


on either side of center sill


107


. A center beam structure


109


extends upward above the center sill


107


and extends longitudinally on a upper portion of the car body


102


between a pair of upwardly extending bulkheads


111


located at ends


103


.





FIG. 3

illustrates a portion of an example of an upper rail


112


in greater detail. Upper rail


112


is attached using any available securing means (e.g., welds, bolts, flanges, and the like) to the top of bulkheads


111


. Upper rail


112


has a width of about three feet and extends the entire length of car


101


between ends


103


. Upper rail


112


comprises structural steel tubing and sheet formed in an angled or rounded gutter. A plurality of spaced apart transverse members


201


span across upper rail


112


at regular intervals. Key holes


202


are formed in each end of transverse members


201


. Key holes


202


are designed to receive and removeably couple to one end of a cable


113


used to secure load


114


during transport.




As seen in the cross-section view of

FIG. 4

, cargo


114


is supported by cross-bearing members


301


attached to or formed integrally with center sill


107


and side sills


108


. A deck sheet


302


forms a floor of flatbed car


101


. A riser


303


formed of sheet steel provides a cargo-supporting top surface sloped slightly toward center beam


109


. Cargo


114


is secured by cables


113


extending from upper rail


112


to winches


304


mounted on side sill


108


. Cables


113


are tightened and loosened as needed during loading and unloading of cargo


114


using winches


304


that may be hand or motor powered winches to meet the needs of a particular application.





FIG. 5

, FIG.


6


and

FIG. 7

illustrate plan views of the cable removing mechanism


401


in accordance with the present invention.

FIG. 5

illustrates a top-down view of an exemplary configuration of the present invention.

FIG. 6

shows a front-to-back view of an embodiment of the present invention.

FIG. 7

shows a side view of the embodiment shown in FIG.


6


. FIG.


8


and

FIG. 9

show perspective views of the mechanism


401


shown in

FIGS. 5-7

. The various features are best understood with reference to FIG.


5


through

FIG. 9

together. It must be understood that many variations to the physical structure, appearance, and materials used will be readily apparent. For example, the preferred embodiments are made using tubular steel and sheet steel joined together by welds. However, other materials including other rigid metals, composite materials, and even plastics or ceramics may be substituted without departing from the basic teachings of the present invention. Likewise, the preferred embodiment is adapted to be manipulated using a conventional forklift, but any available lift mechanism including tractors, hand operated lifts, and overhead lifts and cranes may be substituted without departing from the present invention.




Cable removing mechanism


401


comprises a receiver end


402


adapted to couple to a lift mechanism and a claw end


403


adapted to remove cable tie downs from key hole slots


202


shown in FIG.


2


. Receiver end


402


is attached to claw end


403


by welding, for example. It is contemplated that other attachment and fabrication techniques will provide suitable results. Although cable removing mechanism


401


is preferably fabricated from high strength structural steel for durability, the relatively low load placed on the operating components is adaptable to lower strength materials to reduce weight and manufacturing cost.




Receiver end


402


comprises two receivers


404


where each receiver defines a cavity


405


sized to allow one tine of a fork lift to slide in and out without binding. Each receiver


404


is formed in the example by a pair of substantially parallel 3″ rectangular cross section tubular steel bars


406


. The two bars


406


are, for example, about four feet long and spaced apart sufficiently to accommodate the width of the forklift tine. The upper and lower bounds of cavity


406


are defined by, for example, ½ sheet steel welded along the upper surface of at least a portion of bars


406


. Sheet steel portions may extend along the entire length of bars


406


, or along only a portion as shown in

FIG. 4

to meet the needs of a particular application. The specific size and thickness values disclosed herein are for illustrative purposes only and are not intended to be a limitation of the present invention.




Claw end


403


comprises a claw bar


411


attached to a plurality of claw assemblies


412


. Each claw assembly


412


corresponds to a cable


113


that can be removed in one pass during operation. In other words, the three claw assemblies


412


enable cable removing mechanism


401


to remove up to three cables


103


simultaneously. A greater or lesser number of claws can be provided to meet the needs of a particular application.




Claw bar


411


is approximately ten feet long in the particular example and comprises 3″ tubular steel having a rectangular cross section. Claw bar


411


is attached to each receiver


404


by welding or other equivalent fabrication technique. Receivers


404


extend horizontally away from claw bar


411


so that the receiver end in which the fork lift tines are inserted is located distally from the claw bar


411


.




Claw assemblies


412


are attached to or integrally formed with claw bar


411


in an aligned, spaced apart arrangement. The spacing between adjacent claw assemblies


412


is chosen to correspond to the spacing between cables


103


on a center beam railcar


101


to be unloaded. Accordingly, claw assemblies


412


will typically, but not necessarily, be uniformly distributed along claw bar


411


.




Each claw assembly


412


comprises a downtube


413


and a hook portion


414


. The downtube


413


is rigidly affixed to both the claw bar


411


and the hook portion


414


. Downtubes


413


comprise about 6″ long sections of 3″ tubular steel having a rectangular cross section. Hook portions


414


have a flat end that attaches to the corresponding downtube


413


and a tapered end located distally from the flat end. The tapered end is given sufficient taper to aide in engaging cables


103


during operation, and in some instances may have little or no taper. Hook portions


414


all extend laterally away from their respective downtubes


413


in the same direction so that the taper ends all point in the same direction. In

FIG. 4

the taper ends point to the left of the page, however an equivalent implementation is enabled if all the taper ends point to the right of the page.




Optionally the invention is implemented with a safety screen assembly


501


. Safety screen assembly


501


protects a lift operator working below the cable removing device


401


from injury caused by cables


113


flying off the top of car


101


once disengaged from key holes


202


. As the cables


113


are typically several feet long comprising heavy steel, they present a serious risk of injury when falling. Safety screen assembly


501


comprises a generally rectangular shaped screen


502


comprising any material that does not unacceptably block the operators line of sight yet provides protection from the falling cables


113


. In a particular implementation, safety screen assembly


501


is about ten feet wide and about three to four feet high. A steel screen or mesh is used in the particular implementation, but transparent plastics, netting, and the like may be readily substituted as equivalents.




Screen


502


is supported by frame


503


comprising 1″ diameter tubular steel having a rectangular cross section in the preferred implementation. Frame


503


can also be made from lighter weight materials and can be eliminated in cases where the material chosen for screen


502


is self supporting. Frame


503


is attached by hinges


506


to screen bar


504


. Hinges


506


enable screen


502


to swing down in operation (i.e., when the cable remover assembly


401


is lifted off the ground) and to store neatly beneath receivers


404


when the cable remover mechanism


404


is on the ground. Screen bar


504


comprises a bar of structure steel tubing having, for example, a 3″ diameter and approximately ten foot length. Screen bar


504


is attached by welding or an equivalent fabrication process to the under side of each receiver


404


at about 12″ from the receiver end


402


.





FIG. 10

illustrates a top portion of a rail car in which the present invention is operable while

FIG. 11

illustrates a top-down view of a portion of FIG.


10


. These figures show enlarged views of what is shown and described in reference to

FIG. 1

, FIG.


2


and

FIG. 3

to ease understanding. Essentially, cable


113


, includes an end such as a chain that adapts to fit into a removeably locking relationship with keyholes


202


. Cable


113


is taut when transporting a load.




FIG.


12


-

FIG. 19

illustrate a typical method of using the cable removing apparatus


401


. As shown in

FIG. 12

, safety gate assembly


501


is sized and hinged so as to fold under cable remover


401


when positioned on the ground or other flat surface. Initially, a forklift


601


is positioned with its mast


602


in a lowered position and the fork times aligned with cavities


405


. Forklift


601


drives its fork times into the receiver cavities


405


as shown in FIG.


12


.




Desirably, the receiving end


402


is equipped with optional safety chains


701


(shown in FIG.


7


-

FIG. 9

) affixed to any convenient position on cable removing mechanism


401


. The safety chains


701


are wrapped around a portion of mast


602


to prevent mechanism


401


from falling from the tines of forklift


601


in operation. Similarly, a second safety chain (not shown) can be used to secure safety gate assembly


501


in a closed position during storage and non-use. Although these features are not specifically illustrated they are readily implemented using available mechanisms and assembly techniques.




In operation, cables


113


are typically loosened prior to loading the cable remover mechanism


401


onto lift


601


. It is recommended that cables


113


be loosened as much as permitted by the winch mechanism to prevent binding of cable


113


when removed. Even when tightened there is a small space between the top of cargo


114


and some portion of cables


113


, and this space is increased when cables


113


are loosened. This space allows the hook ends


414


of claw assemblies


412


to be inserted underneath the loosened cables


113


and above cargo


114


.




Once the cables are loosened, the remainder of the process in accordance with the present invention can be completed while the operator remains in the safety of lift


601


. Mast


602


is raised to a level that places claw end


403


a few inches, for example 2-6 inches, above the top of load


114


. Forklift


601


is then driven forward as suggested in FIG.


12


and roughly aligned to cables


113


such that the open hook end


414


of each claw assembly


412


is a few inches to the side of a corresponding cable


113


as shown in FIG.


12


A. The claws are aligned to the left of cables


113


in the particular example due to the direction of hook ends


414


. Claws aligned to the right of cables


113


would be appropriate if the direction of hook ends


414


were reversed. Further rough positioning may be accomplished as shown in FIG.


13


and

FIG. 13A

to lower the claws into vertical alignment beneath cables


113


.




Once the rough alignment is completed, the cable removing mechanism


401


is side-shifted as shown in

FIG. 13B

using lift


601


to maneuver the hook ends


414


into position between the top of cargo


114


and cables


113


. It is useful at this stage to raise mast


602


slightly as shown in FIG.


14


and

FIG. 14A

while visually checking cables


113


to verify proper engagement between cables and claw assemblies


412


. Proper engagement means that cables


113


are aligned to engage claw assemblies


412


at a position that will support the force required to disengage the cables


113


from key holes


202


.




Once engagement and position is visually verified, mast


602


is raised once again to lift claw assemblies


412


clear of the upper rail


112


as shown in

FIGS. 15 and 15A

. A few inches clearance (i.e., two to four inches) is all that is required and a wide tolerance is permitted at this stage. The process in accordance with the present invention is completed by driving the lift


601


forward (i.e., towards car


101


) as suggested in

FIG. 15

until ends of cables


113


are pushed forward in key holes


202


to release the cables. Detail of this operation is shown in FIG.


15


C. Cables


113


will either fall immediately of their own weight (e.g., as shown in FIG.


15


B and FIG.


19


), or may need to be removed by backing lift


601


away from car


101


until the cables fall free to the ground as shown in

FIG. 16

,

FIG. 17

, FIG.


17


A and FIG.


18


. In either case, safety screen assembly


501


prevents operator injury from the falling cables.




The steps discussed above are repeated for each set of cables


113


on both sides of car


101


. In practice the operations can be performed safely in about fifteen to twenty minutes per car


101


using a single operator. It is contemplated that with skill and experience this time can be improved.




Although the invention has been described and illustrated with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example, and that numerous changes in the combination and arrangement of parts can be resorted to by those skilled in the art without departing from the spirit and scope of the invention, as hereinafter claimed.



Claims
  • 1. A method for removing cable tie downs from a center beam railcar having an upper beam to which cable ends of the cable tie downs are removably attached, the method comprising the steps of:loosening a cable tie down to create cable slack; attaching a cable removing apparatus to a lift mechanism having a cable claw located distally from the lift mechanism, the cable claw being rigidly mounted within the cable removing apparatus and including an open hook end rigidly mounted and configured to receive and contact cable tie downs; engaging a portion of the loosened cable tie down with the cable claw using the lift mechanism to position the cable claw adjacent the loosened cable tie down and moving the cable claw substantially parallel to the upper beam, whereby the loosened cable tie down is received into the open hook end of the cable claw; and moving the cable removing apparatus with the cable claw towards the upper rail of the center beam railcar until the cable tie down engaged by the cable claw is released from a keyhole in the upper rail.
  • 2. The method of claim 1 wherein the step of engaging comprises:positioning the cable claw so that a tip end of the open hook end is adjacent to the loosened cable tie down and clear of cargo carried in the railcar; and side shifting the cable claw in the direction of the cable tie down such that the tip end enters a space between the cargo and the cable tie down created by the cable slack.
  • 3. The method of claim 1 further comprising the step of lifting the cable claw above the upper rail of the center beam railcar before the step of moving the cable removing apparatus towards the upper rail.
  • 4. The method of claim 1 further comprising:moving the cable removing apparatus with the cable claw away from the upper rail until the released cable tie down is pulled free of the railcar and falls to the ground.
  • 5. The method of claim 1 further comprising the step of deploying a safety screen between the lift mechanism and the cable tie downs.
  • 6. The method of claim 1 wherein the step of attaching the cable removing apparatus further comprises the step of securing the cable removing apparatus to the lift mechanism using a chain tie down.
  • 7. An apparatus for removing tie down cables from a center beam rail car loaded with cargo, the apparatus comprising:a support beam having a width selected to be greater than the span between a number of tie down cables on the center beam rail car; a plurality of hook-shaped cable claws rigidly attached in a spaced apart, downwardly extending manner to the support beam, wherein the cable claws include a hook end having an opening for receiving the tie down cables and being in a plane substantially parallel to the support beam; and at least one lift sleeve with a longitudinal axis transverse to the support beam rigidly attached to the support beam and having a receiving end for attaching to an external lift mechanism.
  • 8. The apparatus of claim 7 wherein the cable claws are spaced from each other by a spacing substantially similar to cable-to-cable spacing in center beam flatcars.
  • 9. The apparatus of claim 7 wherein the cable claws comprise:a down tube welded to the bottom of the support beam; and the hook ends are welded to the bottom of the down tube and extend away from the down tubes in a direction parallel to the support beam.
  • 10. The apparatus of claim 9 wherein the hook end of each cable claw extends away from the corresponding down tube in a single direction.
  • 11. The apparatus of claim 7 wherein the lift sleeve comprises a pair of parallel spaced apart tubular steel bars attached to each other by a plate of sheet steel.
  • 12. The apparatus of claim 7 further comprising at pair of lift sleeves adapted to receive the tines of a fork lift.
  • 13. The apparatus of claim 7 further comprising a safety gate attached by hinges to the cable removing apparatus near a receiving end of the at least one lift sleeve.
  • 14. An unloading system for a center beam flatcar comprising:a center beam railcar having a deck with a cargo loaded thereon, the center beam railcar having an upper rail extending along the top of the center beam, a plurality of key holes formed in the upper rail, and a plurality of winches attached to the deck; a plurality of cables securing the cargo, each cable having a first end coupled to one of the key holes and a second end attached to one of the winches; a lift mechanism with a lift member movable in vertical and horizontal directions; and a cable removing mechanism that removably attaches to the lift mechanism, wherein the cable removing apparatus includes a plurality of spaced apart aligned cable hooks positioned at a first end having a hook end with an opening in a plane transverse to a longitudinal axis of the lift member and a lift mechanism receiver located at a second end and wherein the cable hooks extend downwardly a sufficient distance to engage a loosened cable tie down from above the load.
  • 15. The system of claim 14 herein the lift mechanism comprises a forklift and the lift member comprises a fork lift tine.
  • 16. A cable removing device for use in detaching an end of a tie down cable from a center beam flatcar, wherein the center beam flatcar includes an upper rail with a plurality of transverse members having key holes for receiving and removably coupling to the end of the tie down cable when a load is bound to the center beam flatcar, comprising:a receiver end comprising a cavity configured for receiving a lifting member of a lift mechanism, wherein the received lifting member abuttingly contacts the cavity to vertically and horizontally position the cable removing device relative to the center beam flatcar; and a claw end comprising a claw bar connected to the receiver end on a side distal to the cavity, wherein the claw end further comprises a first claw assembly including a downtube rigidly attached to the claw bar and extending transverse to the claw bar and a hook portion rigidly attached to the downtube configured for receiving and contacting the tie down cable, the hook portion comprising a contact member extending laterally away from the downtube to form an open end in a plane transverse to an axis of the lift member; wherein the open end of the first claw assembly is configured for initially receiving and contacting the tie down cable with the downtube acting as a horizontal load bearing member when the lift mechanism is operated to move the lifting member in a direction substantially parallel to the upper rail of the flatcar.
  • 17. The device of claim 16, wherein the contact member includes a flat end proximal to the downtube and a tapered end distal to the downtube for engaging the tie down cables and guiding the tie down cables into the claw assembly, whereby the tie down cables abuttingly contact the downtube when the lifting member is moved in a direction substantially parallel to the upper rail of the flatcar and abuttingly contact the flat end when the lifting member is moved in a direction traverse to the upper rail.
  • 18. The device of claim 17, wherein the claw end comprises a second claw assembly rigidly attached to the claw bar with a tapered end and a flat end forming a second open end positioned to open in a same direction as the first claw assembly and to be positioned substantially in the same plane as the open end of the first claw assembly.
  • 19. The device of claim 18, wherein the first claw assembly and the second claw assembly are a separation distance apart as measured along an axis of the claw bar, the separation distance being about a separation distance between key holes in adjacent ones of the transverse members, whereby the first and second claw assemblies are operable to concurrently engage and detach a first and a second, adjacent tie down cable.
  • 20. The device of claim 16, wherein the downtube of the claw assembly is tubular steel with a rectangular cross section selected to resist shearing.
  • 21. The device of claim 16, wherein the receiver end has a length of at least about 4 feet as measured along an axis of the cavity.
  • 22. The device of claim 16, further comprising a safety screen assembly including a frame rotatably attached to a portion of the receiver end proximal to the cavity and a screen attached to the frame configured to block passage of the tie down cable, wherein the frame is free to rotate downward due to gravity into a plane transverse to a plane passing through the receiver end.
  • 23. The device of claim 1, wherein the cable removing apparatus comprises a plurality of the cable claws rigidly mounted with each having the open hook end aligned and opening in the same direction and being spaced apart in the cable removing apparatus a distance selected to approximate distances between adjacent locations on the upper beam for removably attaching the cable ends of the cable tie downs and further wherein the attaching and engaging steps are performed concurrently for each of the cable claws.
RELATED APPLICATIONS

Claim for priority is made under 35 U.S.C. 119 or 35 U.S.C. 120 to co-pending U.S. provisional patent application Ser. No. 60/140,237, Filed Jun. 22, 1999.

US Referenced Citations (12)
Number Name Date Kind
2558388 Richardson Jun 1951
2644598 Winslow Jul 1953
3053405 Holmberg, Jr. et al. Sep 1962
3930585 Lynch Jan 1976
4160509 Switzer Jul 1979
5024567 Dominguez Jun 1991
5186586 Stephenson, Jr. Feb 1993
5460465 Little Oct 1995
5486083 Thompson Jan 1996
5626083 Saxton May 1997
5876164 Hamelin et al. Mar 1999
5899646 Tatina May 1999
Foreign Referenced Citations (5)
Number Date Country
2444580 Jan 1976 DE
4136285 May 1993 DE
1193943 Nov 1959 FR
937503 Sep 1963 GB
581077 Nov 1977 RU
Provisional Applications (1)
Number Date Country
60/140237 Jun 1999 US