Railroad tie plating machine and method

A plating system for attaching a pair of tie plates to a wooden railroad tie with screw spikes such that the tie plates are aligned and in gauge. A predrilling system is used to predrill holes in the appropriate position on the railroad tie according to the line end of the tie prior to loading the tie into the plating system. The plating system clamps the railroad tie in registration according to the line end of the tie, and holds the tie plates in the appropriate position while a pair of hydraulic screw-presses turn screw spikes to fasten the tie plates to the railroad tie in gauge, centered and aligned on the railroad tie.

FIELD OF THE INVENTION

The invention pertains to the mounting and attachment of tie plates to wooden railroad ties.

BACKGROUND OF THE INVENTION

Tie plates are often made of cast iron or rolled steel and are attached on the top surface of wooden railroad ties to support the rails. A fastening assembly, spikes, or both, are used to mount the rail to the tie plate. The tie plate has a rail seat into which the rail sits when mounted in the field. Collars and holes are often provided on both sides of the rail seat to enable clips and spikes to secure the rails to the tie plate. Exemplary tie plate10A,10B are shown on a railroad tie12inFIGS.3-7.

The tie plate10A,10B increases the bearing area and holds the rail16A,16B to correct gauge, or distance between the rails. In the modern railroad industry, gauge is 56.5 inches measured from inside rail to inside rail. The part of the tie plate under the rail base is called the rail seat and is angled slightly, setting the cant of the rail an inward rotation from the vertical. The usual slope is 1.4 degrees. The top surface of the tie plate also has shoulders that fit against the edges of the base of the rail. The shoulders and the canted channel bottom form the rail seat.

It is important that the tie plates be mounted on the railroad tie at the correct spacing and correct distance from the line end of the railroad tie in order for the rails to be at gauge when laid. It is also important that the tie plates be mounted straight and centered on the railroad tie and that the cant of the seat be sloping inward when the rail is laid. If the tie plates are not mounted correctly, or if the rail falls out of gauge through use, adjustments must be made in the field to maintain gauge. It is an object of this invention to reduce errors when mounting tie plates and to also reduce maintenance by mounting the tie plates within a closer tolerance than is currently required in the railroad industry.

Tie plates are typically attached to the wooden railroad ties with common spikes or with screw spikes. The present invention pertains to attaching tie plates to railroad ties with screw spikes. An exemplary screw spike14is shown inFIG.5. The screw spike14has a square head to facilitate attachment with an air gun or pneumatic ratchet. One-half inch holes are typically drilled in the top surface of the wooden railroad tie12for the screw spikes14. Tie plates are sometimes attached in the field, but it is often desirable to supply pre-plated railroad ties to the job site.

The process involves placing the tie plates over holes drilled in the railroad tie. Predrilled railroad ties are typically supplied to the field. As mentioned, it is important that the tie plates be placed so that the cant slants inward. The worker then sets the screw spikes one at a time through the screw holes in the tie plate into the respective drilled hole using a sledge. The object is to set the screw spike straight, but this is difficult to do on a reliable basis. Errors in gauge can occur if the screw spike is not set vertically. An air gun ratchet is used by the worker to screw in the screw spike after it is set. The worker tries to keep the socket centered over the drilled hole, but this is difficult to achieve for a number or reasons including that the air gun typically weighs about 80-100 pounds. If the worker does not keep the socket vertically over the hole, or if the screw spike is set crooked, the tie plate can move out of position when it is being attached, which may cause it to fall out of gauge. In addition, the screw hole can get bored out or stripped if the worker does not stop the air gun in a timely manner after the screw spike if fully secure. Needless to say, when hand fastening with an air gun, it is difficult to be reliably accurate even if screw holes are accurately predrilled.

SUMMARY OF THE INVENTION

The invention pertains to a method of attaching a pair of tie plates to a wooden railroad tie with screw spikes. Use of the method results in tie plates being reliably aligned and in gauge. The method attaches the tie plates to tighter dimensional tolerances than is typical with previous attachment methods. The first step in the method is to provide a railroad tie with screw holes predrilled into the top surface of the railroad tie. The predrilled railroad tie is conveyed into a plating system, for example using a gravity fed conveying system and a kicker to load the railroad tie onto rollers that convey the railroad tie into the plating system lengthwise. The plating system has two plate attachment stations: one for each tie plate that is being attached to the top surface of the railroad tie. Each plate attachment station has a holding press with a foot that holds the respective tie plate reliably in place on the predrilled railroad tie. Each plate attachment station also has a screw press to hold and fasten screw spikes to attach each tie plate while it is being held in place by the foot on the respective holding press. An actuation mechanism, such as a hydraulic cylinder and mechanical linkage, lifts and lowers each holding press and its foot.

Once the predrilled railroad tie is conveyed to the plating system, its line end is aligned in registration with a reference position, for example by abutting the line end against an end stop. The screw holes are previously drilled at locations in registration with the line end as is discussed in more detail below. Then, the predrilled railroad tie is clamped in the registered position such that a top surface of the predrilled railroad tie lies substantially in a horizontal plane. At this point in the method, the first and the second tie plates are placed on the top surface of the predrilled railroad tie, and are held securely in place against the top surface of the predrilled railroad ties with the foot of the holding press in the respective plate attachment station. More specifically, the first and second tie plates are held in registration along the aligned, clamped railroad tie by the press feet so that rails mounted in the tie plates will be in gauge. Preferably, the clamping step involves the use of two self-centering clamps that clamp the lateral sides of the railroad tie and an end clamp that pushes against the end of the railroad tie opposite its line end when the line end is abutting the end stop. The self-centering clamps are useful to keep the tie plates centered on the railroad tie even if the width of the tie varies. As discussed, the railroad tie is clamped in a similar fashion when predrilling the screw holes. Desirably, each foot pushes downward on the respective tie plate with a significant amount of force, and keeps the tie plate centered on the railroad tie, positioned at the proper distance from the line end along the length of the railroad tie and orientated straight. The tips of the screw spikes are then placed through the screw holes in the tie plates and into the predrilled holes and the heads of the screw spikes are placed in the respective sockets on the screw presses. While the railroad tie is aligned and clamped and the first and second tie plates are held against the top surface of the railroad tie with the respective press foot, the screw press in each plate attachment station screws the screw spikes and fasten the tie plates to the top surface of the drilled railroad tie. By virtue of the design, the sockets on the screw presses remain vertically aligned with the screw holes in the ties plates and the holes drilled in the top surface of the railroad tie. In addition, the press feet hold the plates in the correct position and orientation on the railroad tie while the screw spikes are being fastened.

The plating system can include an optional staging plate at each station for holding a tie plate before the holding press in the plate attachment station picks up the tie plate and places it on the aligned and clamped, predrilled railroad tie. The staging plate has upstanding reference pins to that fit into designated screw holes or other physical reference openings in the tie plate so that the tie plate is accurately aligned and orientated when the tie plates are lifted from the staging plate.

In an especially desirable embodiment, the holding press in each plate attachment stations is equipped with an electromagnet that is controlled to engage and release the tie plate as required for lifting. The electromagnet is located on the holding press above and adjacent the foot. Each press foot is preferably made of steel and is configured to nest within the seat or rail channel of the tie plate between a field side shoulder and an inside shoulder. The foot on each holding press is canted to complement the cant of the rail seat of the tie plate that it is configured to lift, move and hold. In use, each holding press is moved over a tie plate placed on the respective staging plate and pressed down so that the canted foot nests in the seat of the tie plate. Then, the electromagnet is activated to magnetically pull the tie plate against the foot. The holding press is lifted and moved into place on the aligned and clamped railroad tie with the tie plate placed in precise alignment on the top surface of the railroad tie by the press foot.

Each screw press includes multiple screw heads, for example four (4) screw sockets. The screw press includes a rotational actuator for each screw head and a linear actuator for lifting and lowering a mounting plate to which the screw heads and rotational actuators are mounted. In the preferred embodiment, the actuators are hydraulically powered, and the hydraulic pumps are controlled by a control system. In each plate attachment station, the tie plate is held in place by the respective press foot and the screw press is lowered to a height appropriate for loading the screw spikes. Loading the screw spikes is preferably done by hand by placing the tip of the screw spike through an appropriate screw hole in the tie plate and into the predrilled hole, and by loading the head of the screw spike into the appropriate socket. When all the screw spikes are loaded, the actuators are activated to screw the screw spikes and fasten the tie plates. A sensor detects when the socket assemblies in the first and second plate attachment stations have moved downward to a pre-selected depth and generates a signal in response thereto. The rotation of the respective screw sockets in the station is deactivated when the signal is received in order to avoid overtightening. The screw press is then lifted to remove the sockets from the heads of the screw spikes. The finished product is then released from the clamps and is transported from the plate attachment stations, ready for shipping to the job site.

The railroad ties are desirably predrilled in a predrilling system having a conveyor that moves in an x-direction. The railroad tie is placed on the conveyor with its length generally perpendicular to the x-direction and its line end facing a predetermined side. The railroad tie is conveyed to a drilling station and is lifted from the conveyor. The line end of the lifted railroad tie is aligned in registration to a reference position in a y-direction which is parallel to the x-direction, for example by pushing the line end against an end stop. The lifted railroad tie is clamped after it is aligned along the line end. Desirably, it is clamped laterally on each end with self-centering clamps and along the end to hold the line end against the end stop. The clamping for predrilling is desirably the same as for fastening the screw spikes. Then, screw holes are drilled in the top surface of the railroad tie for both tie plates while the railroad tie is clamped in the registered position in the drilling station.

The plating system and the predrill system can be configured to drill the holes and screw the screw spikes in pre-selected positions for a specific type and size of tie plate. On the other hand, the drill press and the screw press can be adjustable or reconfigurable. In this case, it is important that the positions of the drill bits and screw sockets be set to be on center with the pre-selected positions for a specific type and size of tie plate. This can be accomplished effectively using set-up templates for the specific tie plates being attached to the railroad ties. For each tie plate, there is a template for positioning the screw heads or sockets and a template for positioning the drill bits. Preferably, the templates are metal plates with holes positioned for the screw sockets and drill bits on center to the appropriate positioning for drilling and screwing in relation to the line end of the railroad tie. The preferred templates also include an indicator designating the line side of the template.

In another aspect, the invention is embodied in a plating system configured to implement the above described method in varying degrees of detail.

DETAILED DESCRIPTION

FIG.1illustrates a plating system20that is configured to attach tie plates10A,10B to a predrilled railroad tie12in accordance with an exemplary embodiment of the invention.FIG.2illustrates a predrilling system100designed to drill screw holes24in the railroad tie12prior to attaching the tie plates10A,10B.

Referring first toFIGS.3through7, the finished product from the plating system20is a railroad tie12with tie plates10A,10B attached to its top surface with screw spikes14. The tie plates10A,10B are attached in registration to the line end12L of the railroad tie12and are mounted so that rails16A,16B are in gauge with reference to the line end12L when the rails16A,16B are mounted in the tie plates10A,10B. The railroad ties12, as mentioned, will have predrilled holes24(FIG.2) and will have been treated with a preservative such as creosote. Typically, the wood ties12will be treated prior to predrilling the holes24. The tie plates10A,10B shown in the exemplary embodiments are Pandrol® Victor plates and the width of the railroad ties12is 6″ within tolerances. The invention can be implemented with railroad ties having different widths and using different tie plates; however, the purpose of the invention to attach the tie plates10A,10B to the top surface of the railroad tie12with screw spikes14. As mentioned, gauge in the US is 56.5″ measured from the inside rail16A to the inside rail16B, seeFIG.6. In the embodiment depicted inFIG.3with Pandrol® Victor plates, the distance from the line end to the field shoulder25A for tie plate10A is 18.5″ and the distance between the field shoulder25A for tie plate10A and the field shoulder25B for tie plate10B should be 65.6875″. Given the configuration of the tie plates10A,10B, these dimensions result in the distance between rails16A,16B inFIG.6being 56.5″+/−the tolerance. In addition to being set a fixed distance from the line end12L and being spaced apart a fixed distance from one another, the tie plates10A,10B also need to lie flat on the top surface of the railroad tie12, be centered across the width of the railroad tie12, and also properly aligned so that the rail sits nicely in the seat of the tie plate. The width of a given railroad tie will often vary from end to end even though this variance is not desirable. Yet, it is important that the tie plates10A,10B be centered across the width of the railroad tie12.FIG.4shows tie plate10B properly centered across the width of the tie plate. InFIG.4, the tie plate10B is placed symmetrically along the longitudinal center line of the top surface of the railroad tie12(although in the field or during production the center line18is not designated or identified on the top surface of the railroad tie12).

Referring toFIG.6A, tie plate10A is shown mounted to the railroad tie12with a rail16A then mounted in the tie plate10A, as it will be in the field. The tie plate10A includes a field side shoulder12A and an inside shoulder27A. A canted channel bottom29A extends between the shoulders25A and27A. The shoulders25A,27A and the channel bottom29A form a seat for the base17A of the railroad tie16A. The seat is designed so that the rail16A fits securely within the seat and is tilted inward towards the other rail, for example at a slope of 1.4°. As mentioned, it is important that the tie plate10A be mounted with the cant properly facing inward. As shown inFIG.4, the plates10A,10B have an additional hole on the field side of the plate10A,10B which is not typically used for attaching the tie plate10A,10B to the railroad tie12, but is helpful for conveniently identifying the field side of the tie plate10,10B.

The invention is used to reliably attach the tie plates10A,10B to the railroad ties12as shown inFIGS.3through6,6A. It can also be used as shown inFIG.7to attach tie plates10to the railroad tie12with an optional elastomeric pad31placed between the tie plate10and the railroad tie12. These elastomeric pads31are used in some applications to dampen vibrations. The inventive method is described herein primarily with respect to attaching the tie plates10A,10B directly to the top surface of the railroad tie12, but it should be understood that the method can be modified to include the use of the optional elastomeric pad31as well.

Referring now toFIG.1, predrilled railroad ties12are loaded onto a gravity feed conveyor21. The predrilled railroad ties12are loaded with the lines end12L on the left of the feed conveyor21. The line side12L of the predrilled railroad ties12is marked as is common in the art. The predrilled railroad ties12are loaded onto the conveyor30for the plating system20, which comprises powered rollers to move the loaded predrilled railroad tie12lengthwise into a first and second plate attachment station22A,22B. After the tie plates10A and10B are attached, the powered rollers30move the railroad tie12to a gravity-fed output conveyor23as a finished product.FIG.1also shows in phantom a railroad tie loaded into the first and second plate attachment stations22A,22B. An end stop32is shown on the downstream side of the plate attachment stations22A,22B. The line end12L of the railroad tie12is pushed against the end stop32to register the longitudinal position of the railroad tie12. The end stop32is mounted to a hydraulic lift so that it can be raised to allow the railroad tie12to be conveyed away from the plate attachment stations22A,22B after the tie plates10A,10B have been attached. A hydraulic end clamp (not shown) pushes against the other end of the railroad tie12to hold the railroad tie12and the line end12L against the end stop32.

Once the railroad tie12is loaded into the first and second plate attachment stations22A,22B, it is first lifted, and then it is clamped. Self-centering clamps36A,36B (not shown inFIG.1) clamp the lateral sides of the railroad tie12, so that the railroad tie is centered within the first and second plate attachment stations22A,22B. Each plate attachment station22A,22B includes a staging plate38A,38B. An operator places tie plates10A,10B on the respective staging plate38A,38B to ready the system20for attaching the plates10A,10B to the railroad tie12. Reference numbers10A,10B inFIG.1refer to stacks of tie plates10A,10B waiting to be loaded by the operator on the respective staging plate38A,38B. Each plate attachment station22A,22B includes a holding press40, seeFIGS.13A-13B, and a screw press42, seeFIG.11.

Referring toFIGS.13A and13B, the holding press40includes a main arm42that is lifted vertically and moved horizontally by hydraulically controlled motors (not shown inFIGS.13A and13B). A foot44is mounted to the bottom of each press arm42. Each foot44is made for example from steel, and is configured to nest within the seat of the tie plate10. More specifically, the foot44nests between the shoulders25,27of the seat, and also lies flat against the bottom wall29of the seat. The bottom wall29is canted towards the inside of the tie, and accordingly the bottom of the foot44is likewise canted so that it complements and fits flat along the canted bottom wall29of the seat of the tie plate10. Each holding press40also includes an electromagnet46. A control system activates the electromagnet46to lift and release the tie plate10as required. The lifting and releasing of the tie plates is shown in more detail with respect toFIGS.15A through15J. Briefly, the holding press40is lowered over a tie plate10located on the respective staging plate38such that the foot44nests within the seat of the tie plate. Then, the electromagnet46is activated to pull the tie plate10against the press foot44, and the arm42of the holding press40is lifted and moved over the railroad tie12. At this point in the process, the railroad tie12is lifted and clamped in a registered position within the first and second plate attachment stations22A,22B. The arm42of the holding press40is then lowered so that the tie plate10is pressed against the top surface of the railroad tie12in the registered position. The holding press40continues to hold the tie plate10in the registered position against the top surface of the railroad tie12while the screw spikes14are set in place as shown inFIG.13Aand also while the screw heads48are turned to fasten the tie plate to the railroad tie12. The continued holding of the tie plate10in the registered position while fastening the tie plate10to the railroad tie12is important to ensure that the tie plate10does not move during the fastening process.FIGS.13A and13Balso show a sensor50that detects when the screw heads48have lowered to an appropriate distance for complete tightening of the screw spikes14without over-tightening. The sensor50provides a signal to the control system to stop rotation of the screw heads48when the appropriate height is detected. The control system also stops the screw presses from lowering at the appropriate time. InFIGS.13A and13B, the sensor50is a proximity sensor which senses the presence of an enlarged collar52on one of the screw heads48.

Each plate attachment station22A,22B includes a screw press42as shown inFIG.11. Referring now toFIG.11, the screw press42in each plate attachment station22A,22B includes multiple screw heads48, preferably four (4), as shown inFIGS.13A and13Bfor example. The screw heads48are turned by hydraulically powered, rotational actuators56that are mounted to adjustable plates60attached to a base plate54. A hydraulic lifting cylinder58is connected to the base plate54to raise and lower the base plate54and the screw heads48. Each of the screw heads48includes a socket62that is configured to fit the square head of the screw spikes14. The sockets62can be lifted relative to the other components of the screw head48in order to facilitate loading of the square head of the screw spikes14, when the screw press42is lowered to a position for loading the screw spikes14prior to activating the rotational actuators56and the linear actuator58to turn and lower the screw spikes14into the railroad tie12.

Now referring toFIGS.2and12, the predrilling system100includes a drilling station102that has a first drill press104A and a second drill press104B. InFIG.2, railroad ties12are conveyed from right to left. When the railroad tie12is conveyed into the drilling station102, it is lifted and clamped with the line end12L pushed against an end stop (not shown inFIG.2) to register the position of the railroad tie12in the drilling station102. The drilling station102also has self-centering clamps to clamp the railroad tie12laterally in a similar fashion as is done in the plating system20. Each drill press104A,104B includes four (4) one-half inch drill bits. Referring toFIG.12, the drill bits106are driven by rotational hydraulic actuators108. Each drill press104is raised and lowered using a hydraulic linear actuator110that is connected to a base plate112for the drill press. The rotational actuators108are mounted to adjustable plates114which in turn are attached to the base plate112. In accordance with the invention, the positioning of the drill bits106is on center with the holes in the tie plate10being attached to the railroad tie12and also on center with the screw heads48and sockets62. It should be understood that similar hydraulic actuators can be used for the screw presses42and the drill presses104. Referring again toFIG.2, once the screw holes24are drilled in the top surface of the railroad tie12, the clamping is released and the tie12is lowered and conveyed from the drilling station102. At this point the railroad tie12is ready for loading into the plating system20.

It is desirable that the drill presses104and the screw presses42be reconfigurable so that the equipment can be used to attach tie plates10having screw holes in different positions than other tie plates. With this concept in mind,FIG.10shows a top view of the base plates54,112that are used in the screw presses42and the drill presses104. Adjustable plates60,114are attached to the base plates54,112. The adjustable plates60,114are designed with an opening66and an annular shoulder68to hold the respective rotational actuator56,108on center on the respective adjustable plate60,114. The adjustable plates60,114also have slots70to enable the position of the adjustable plate60,114to be adjusted with respect to the base plate54,112. The slots70shown inFIG.10allow the plates60,114to move laterally inFIG.10, although the concept could be applied to repositioning in other directions if desired. Of course, it is imperative that the screw holes24in the top surface of the predrilled railroad tie12be in line with the screw holes in the respective tie plates10A,10B, in line with the screw heads48in the respective plate attachment stations22A,22B, and also in registration with the line end12L of the railroad tie12. To help accomplish this task, a metal template64as shown inFIG.8can be used to set the position of the screw heads48in both the first and second plate attachment stations22A,22B. The size of the round openings72in the metal template64is selected to fit over the collars of the sockets62on the screw heads48. The triangular openings74point to the line end64L of the template64. The position of the circular holes72is selected with respect to the line end64L so that the screw heads48are on center with the desired location for the screw holes in the railroad tie12. The adjustable plates60in the drill presses42are adjusted so that the sockets62fit in the openings72with the template64held in registration against the end stop or another suitable reference point, and then the adjustable plates60are tightened in place to the base plate54. Similarly,FIG.9shows a metal template116for the drill bits106in the drill presses104. The circular openings118are sized to fit around the diameter of the drill bits106. The triangular openings120point towards the line end116L of the template116. The adjustable plates114are moved until the drill bits106pass through the round openings118when the line end116L is held in registration against the end stop (or other suitable reference point). Then, the adjustable plates114are tightened against the base plate112. In this manner, the drill bits106and the screw sockets62are appropriately located in registration for the appropriate tie plates.

The preferred steps for predrilling holes24in the railroad ties12are now discussed in relation to schematicFIGS.14A through14H.FIGS.14A through14Dillustrate the operation of the drilling station102with reference to components on one side of the drilling station, Reference characters without the designation A or B are used to generally refer to similar components in each side of the drilling station102. InFIG.14A, the railroad tie12is being conveyed on a conveyor122towards the drilling station102. The line end12L of the tie12is marked and is set on a predetermined side. The railroad tie12is conveyed crosswise into the drilling station102until it hits a stop124. The stop124is desirably movable between an up position and a down position and is actuated in response to a motion sensor recognizing that a railroad tie12is moving into the drilling station102.FIG.14Bshows the railroad tie12located in the drilling station102and abutting the raised stop124.FIG.14Cshows the railroad tie12being lifted upward off the conveyer122. More, specifically,FIG.14Cshows a hydraulic lift126lifting one end of the railroad tie12for purposes of illustration; however, it should be understood that another hydraulic lift126is provided to lift the other end of the railroad tie. The railroad tie12is lifted so that its top surface remains horizontal.FIG.14Dshows the next step in the process in which the lifted railroad tie12is clamped with hydraulic, self-centering clamps128. The clamp arms128clamp against the lateral side of the railroad tie12. Again, for purposes of illustration,FIG.14Dshows a set of lateral clamps128near one side of the railroad tie12, but it should be understood that similar clamps are located on the other side of the railroad tie12. In this manner, the self-centering clamps128center both sides of the railroad tie12, which is important for drilling the holes24on center when the width dimensions of the railroad tie vary.

FIG.14Eshows the railroad tie12in the drilling station102as viewed from the input conveyor. InFIG.14E, the lift on each side126A,126B have lifted the railroad tie12above the conveyors122A,122B. In addition, the self-centering clamps128A,128B have clamped the lateral sides of the railroad tie12. The line end12L of the railroad tie12has not yet been pushed against, or to be in registration with, the end stop130. The hydraulic push arm132on the opposite side of the end stop130is used to push the tie12against the end stop130. The drill presses104A,104B remain in the up position at this stage in the process.FIG.14Fshows the next step in the process after which the lifted railroad tie12has been pushed with the actuator arm132so that the line end12L of the tie is pressed against the end stop130. InFIG.14F, the drill presses104A and104B remain in the up position.

With the railroad tie12lifted and clamped to be on-center and in registration against the end stop130, the drill presses104A,104B are lowered to drill holes24in the top surface of the railroad tie12as shown inFIG.14G.FIG.14Hshows the next step in the process in which the drill presses104are lifted, the clamps128are opened, the push actuator132is retracted, and the lifts126are lowered to set the railroad tie12with predrilled holes24on the conveyor122for transport downstream from the drilling station102.

FIGS.15A through15Jschematically depict the steps involved in attaching tie plates10A,10B to a railroad tie12using the plating system12described inFIG.1.FIGS.15Cthrough15F, and15J, illustrate the operation of the both the first and second plate attachment stations22A,22B. Reference characters without the designation A or B are used to generally refer to similar components in each plate attachment station. InFIG.15A, the railroad tie12with predrilled holes24is loaded onto rollers30which are driven to load the railroad tie12into the system20lengthwise.FIG.15Ashows a hydraulically actuated safety shield76preventing access by an operator to the second plate attachment station22B while the railroad tie12is being loaded. A similar hydraulically actuated safety shield76is also present in the system20for the first plate attachment station22A but is not shown because it would block visualization of components behind the safety shield.FIG.15Bshows the railroad tie12being loaded into the system20with the line end12L being stopped by the end stop32. The end stop32is hydraulically actuated so that it can be raised and lowered, as explained previously in order to allow the railroad tie12to exit the system once the tie plates10A,10B have been attached. A sensor detects when the railroad tie12is roughly in position shown inFIG.15B, and in response hydraulic lifts33A,33B are actuated to lift the railroad tie12above the rollers30. The driven rollers are also desirable deactivated.FIG.15Cshows the railroad tie12on the rollers30as depicted inFIG.15Bbut from a different viewpoint.FIG.15Dshows the hydraulic lift33being actuated to lift the railroad tie12above the rollers30. For purposes of illustration,FIG.15Dshows on one lift33, however as shown inFIG.15Ba lift33A,33B is provided at each end of the railroad tie12. The railroad tie12is lifted so that its top surface remains horizontal.

FIGS.15C and15Dalso schematically illustrate a screw press42for the plate attachment station22and a holding press40for the plate attachment station22. InFIG.15C, a tie plate10is being placed on the staging plate38. The staging plate38includes reference pins80that extend upward and are designed to fit into the screw holes or other holes in the tie plate10in order to ensure that the tie plate10is in the proper position and the orientation on the staging plate38.FIG.15Dshows the holding press40moving downward so that the foot of the press engages the channel or the seat of the tie plate10. At this step in the process, the electromagnet46is also actuated to pull the tie plate10against the foot44of the holding press40.

FIG.15Eshows the lifted railroad tie12being clamped with the self-centering clamps36. As shown for example inFIG.15B, there is a set of self-centering clamps36A,36B at each end of the railroad tie12. The self-centering clamps36are desirably of the same construction as those used in the drilling system100, and serve to center the railroad tie12longitudinally even if it does not have a consistent width. At the same time, a hydraulic actuator arm (not shown) pushes the line end12L of the rail against the end stop32. Referring again toFIG.15E, while the lifted railroad tie12is being clamped, the holding press40moves the tie plate10into position over the railroad tie12beneath the respective screw press42.FIG.15Fshows the next step in the process in which the holding press40moves downward to press the tie plate10against the top surface of the lifted and clamped railroad tie12. As described previously, the feet44of the respective holding presses40hold the ties10A,10B in precise registration with the designated position along the railroad tie in reference to the line end of the railroad tie.

InFIG.15G, the respective feet44A,44B of the holding presses are shown holding down the tie plates10A,10B against the top surface of the railroad tie12. The safety shield76is retracted and the operators load the screw spikes14. This is done by putting the tip of the screw spike14through the screw holes in the tie plate and into the predrilled holes24in the top surface of the railroad tie12. The top square head of the screw spikes14is placed in the sockets62of the respective screw heads48.FIG.15Hshows the next in the process in which the screw presses42A,42B are activated to be lowered and to also turn the sockets62in order to screw the screw spikes14into the railroad tie12and fasten the tie plates10A,10B.FIG.15Hshows the safety shield76remaining in the open position during this step of the process although it may be more desirable to close the shield76for this step in the process. It is noted that the screw spikes14are maintained in vertical alignment by the respective screw presses42A,42B when being screwed into the railroad tie12to fasten the tie plates10A,10B. It is also noted that the feet44A,44B continue to hold the tie plates10A,10B in place while the screw spikes14are being screwed into the railroad tie12.

InFIG.15I, the electromagnets have been deactivated and the holding presses have been lifted and moved out of the way. In addition, the screw presses42A,42B are lifted.FIGS.15K and15Jshow the next step in the process in which the clamps36A,36B have been released, the end stop32has been lifted, the lifts33A,33B have been lowered, the railroad tie12is placed on the rollers30, and the rollers30are turned on to transport the finished railroad tie12away from the plate attachment stations22A,22B.FIG.15Jshows the system in the same stage of operation as shown inFIG.15K, but from a longitudinal perspective.

The invention has been described in connection with an exemplary embodiment of implementing the invention. Not all of the above described features are necessary for implementing the broader aspects of the invention. The following claims should be considered when determining whether a given method or machine falls within the scope of the patent.