Patent Publication Number: US-10773735-B2

Title: Rapid discharge door locking system

Description:
TECHNICAL FIELD 
     Particular embodiments relate generally to railcars, and more particularly to a door locking system for rapid discharge railcars, such as hopper cars for carrying bulk materials. 
     BACKGROUND 
     Railway hopper cars transport and sometimes store bulk materials. Hopper cars generally include one or more hoppers which may hold cargo or lading during shipment. Hopper cars are frequently used to transport coal, sand, metal ores, aggregates, grain and any other type of lading which may be satisfactorily discharged through openings formed in one or more hoppers. Discharge openings are typically provided at or near the bottom of each hopper to rapidly discharge cargo. A variety of door assemblies or gate assemblies along with various operating mechanisms have been used to open and close discharge openings associated with railway hopper cars. 
     Transversely oriented discharge openings and gates are frequently coupled with a common linkage operated by an air cylinder. The air cylinder is typically mounted in the same orientation as the operating gate linkage which is often a longitudinal direction relative to the associated hopper. 
     Longitudinally oriented discharge openings and associated doors may provide a quicker discharge than transverse gates. Longitudinally oriented discharge openings and doors are often used in pairs that may be rotated or pivoted relative to the center sill or side sills of a hopper car. Longitudinally oriented discharge openings and doors may be coupled via linkages with a beam operated by an air cylinder. The air cylinder is typically mounted in the same orientation as the operating beam which is often a longitudinal direction relative to the associated hopper. The operating beam may be coupled to the discharge doors by door struts (linkages) that push (or pull) the gates open or pull (or push) them closed as the air cylinder moves the operating beam back and forth. 
     A hopper car is an example of a rapid discharge railcar. In general, rapid discharge railcars may use air cylinders, operating beams, and linkages to operate the bottom outlet doors. 
     SUMMARY 
     According to some embodiments, a railcar comprises an underframe, a hopper coupled to the underframe, a discharge door coupled to the hopper proximate the underframe, and an operating beam coupled to the discharge door and the underframe. The operating beam comprises a lock piston receiving recess. The railcar further comprises an operating cylinder coupled to the operating beam. The operating cylinder comprises a first input and a second input. The operating cylinder is configured to move the operating beam between a first position where the discharge door is in a closed position and a second position where the discharge door is in an open position, wherein activation of the first input causes the operating cylinder to move the operating beam to the first position and activation of the second input causes the operating cylinder to move the operating beam to the second position. 
     The railcar further comprises a discharge door locking system coupled to the underframe. The discharge door locking system comprises a lock piston, a first input, and a second input. The discharge door locking system is configured to move the lock piston between a first position where the lock piston is not engaged with the lock piston receiving recess and a second position where the lock piston is engaged with the lock piston receiving recess. Activation of the first input moves the lock piston to the first position, and activation of the second input moves the lock piston to the second position. 
     The second input of the operating cylinder is coupled to the first input of the discharge door locking system, and the first input of the operating cylinder is coupled to the second input of the discharge door locking system. When the second input of the operating cylinder is activated to move the discharge door to the open position, the first input of the discharge door locking system is also activated to disengage the lock piston from the lock piston receiving recess. When the first input of the operating cylinder is activated to move the discharge door to the closed position, the second input of the discharge door locking system is also activated to engage the lock piston with the lock piston receiving recess. 
     In particular embodiments, the first input and the second input of the operating cylinder and the first input and the second input of the discharge door locking system comprise pneumatic inputs. In other embodiments, the first and second inputs may comprise electrical, mechanical, or hydraulic inputs. 
     In particular embodiments, the second input of the operating cylinder is coupled to the first input of the discharge door locking system via a check valve, and the first input of the operating cylinder is coupled to the second input of the discharge door locking system via a check valve. In particular embodiments, the second input of the operating cylinder is coupled to the first input of the discharge door locking system via a 3-way valve and the first input of the operating cylinder is coupled to the second input of the discharge door locking system via a 3-way valve. In particular embodiments, the second input of the discharge door locking system comprises a spring. 
     In particular embodiments, the discharge door locking system further comprises an operating cylinder actuating valve coupled to the lock piston, the first input of the operating cylinder, and the second input of the operating cylinder. When the lock piston is in the first position, the operating cylinder actuating valve is configured to activate the second input of the operating cylinder to move the discharge door to the open position. When the lock piston is in the second position, the operating cylinder actuating valve is configured to activate the first input of the operating cylinder to move the discharge door to the closed position. 
     In particular embodiments, the discharge door comprises one of a transverse discharge door and a longitudinal discharge door. The railcar may comprise a hopper car. 
     According to some embodiments, a discharge door locking system for a railcar discharge door comprises a lock piston configured to move between a first position where the lock piston is not engaged with a lock piston receiving recess of an operating beam coupled to a discharge door and a second position where the lock piston is engaged with the lock piston receiving recess. The discharge door locking system further comprises a first input and a second input. Activation of the first input moves the lock piston to the first position; and activation of the second input moves the lock piston to the second position. 
     The first input of the discharge door locking system is coupled to a first input of an operating cylinder coupled to the operating beam. The first input of the operating cylinder is configured to, when activated, move the discharge door to the open position. The second input of the discharge door locking system is coupled to a second input of the operating cylinder. The second input is configured to, when activated, move the discharge door to the closed position. 
     In particular embodiments, the first input and the second input of the of the discharge door locking system comprise pneumatic inputs. The second input of the discharge door locking system may comprise a spring. 
     In particular embodiments, the first input of the discharge door locking system is coupled to the first input of the operating cylinder via a check valve, and the second input of the discharge door locking system is coupled to the second input of the operating cylinder via a check valve. In particular embodiments, the first input of the discharge door locking system is coupled to the first input of the operating cylinder via a 3-way valve, and the second input of the discharge door locking system is coupled to the second input of the operating cylinder via a 3-way valve. 
     In particular embodiments, the discharge door locking system further comprises an operating cylinder actuating valve coupled to the lock piston, the first input of the operating cylinder, and the second input of the operating cylinder. 
     According to some embodiments, a method of outfitting a railcar with a discharge door locking system comprises providing a railcar. The railcar comprising an underframe, a hopper coupled to the underframe, a discharge door coupled to the hopper proximate the underframe, and an operating beam coupled to the discharge door and the underframe. The operating beam comprises a lock piston receiving recess. The railcar further comprises an operating cylinder coupled to the operating beam. The operating cylinder comprises a first input and a second input. The operating cylinder is configured to move the operating beam between a first position where the discharge door is in a closed position and a second position where the discharge door is in an open position. Activation of the first input causes the operating cylinder to move the operating beam to the first position, and activation of the second input causes the operating cylinder to move the operating beam to the second position. 
     The method further comprises coupling a discharge door locking system to the underframe of the railcar. The discharge door locking system comprises a lock piston, a first input, and a second input. The discharge door locking system is configured to move the lock piston between a first position where the lock piston is not engaged with the lock piston receiving recess and a second position where the lock piston is engaged with the lock piston receiving recess. Activation of the first input moves the lock piston to the first position, and activation of the second input moves the lock piston to the second position. 
     The method further comprises coupling the second input of the operating cylinder to the first input of the discharge door locking system, and coupling the first input of the operating cylinder to the second input of the discharge door locking system. When the second input of the operating cylinder is activated to move the discharge door to the open position, the first input of the discharge door locking system is also activated to disengage the lock piston from the lock piston receiving recess. When the first input of the operating cylinder is activated to move the discharge door to the closed position, the second input of the discharge door locking system is also activated to engage the lock piston with the lock piston receiving recess. 
     In particular embodiments, the discharge door locking system further comprises an operating cylinder actuating valve coupled to the lock piston, the first input of the operating cylinder, and the second input of the operating cylinder. The method further comprises coupling the first and second inputs of the operating cylinder to the operating cylinder actuating valve. When the lock piston is in the first position, the operating cylinder actuating valve is configured to activate the second input of the operating cylinder to move the discharge door to the open position. When the lock piston is in the second position, the operating cylinder actuating valve is configured to activate the first input of the operating cylinder to move the discharge door to the closed position. 
     According to some embodiments, a railcar comprises an underframe, a hopper coupled to the underframe, a discharge door coupled to the hopper proximate the underframe, an operating beam coupled to the discharge door and the underframe, an operating cylinder coupled to the operating beam via a mechanical operating beam lock configured to move between a first, locked position and a second, unlocked position, and a discharge door locking system coupled to the underframe. The discharge door locking system comprising a lock block slidably coupled to the underframe. The lock block is configured to move between a first position where the lock block prevents the mechanical operating beam lock from moving to the unlocked position and a second position where the lock block does not prevent the mechanical operating beam lock from moving to the unlocked position. 
     In particular embodiments, the discharge door locking system further comprises an air inlet valve. The air inlet valve is configured so that the lock block moves to the first position when compressed air is supplied to the railcar and the lock block moves to the second position when compressed air is removed from the railcar. 
     As a result, particular embodiments of the present disclosure may provide numerous technical advantages. For example, particular embodiments may provide improved door securement with less adjustment. Particular embodiments may include a pneumatically operated discharge door locking system that is automatically synchronized with the discharge door actuating system. For example, synchronizing the discharge door locking system with the operation of the operating cylinder improves the efficiency of the unloading process. Railcars may be unloaded faster, because an operator performs fewer operations. Particular embodiments of the present disclosure may provide some, none, all, or additional technical advantages. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the particular embodiments, and the advantages thereof, reference is now made to the following written description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic drawing in elevation showing a side view of an example hopper car, according to a particular embodiment; 
         FIG. 2  is a schematic drawing in elevation showing an end view of an example hopper car, according to a particular embodiment; 
         FIG. 3  is a schematic drawing showing a cross section view of an example hopper car taken along lines B-B of  FIG. 1 ; 
         FIG. 4  is a block diagram illustrating longitudinal discharge doors underneath an example hopper car, according to a particular embodiment; 
         FIG. 5A  is a block diagram illustrating a discharge door locking system in the unlocked position, according to a particular embodiment; 
         FIG. 5B  is a block diagram illustrating a discharge door locking system in the locked position, according to a particular embodiment; 
         FIGS. 6A and 6B  are block diagrams illustrating a discharge door locking system coupled to the operating cylinder with hall valves, according to particular embodiments; 
         FIG. 7  is a block diagram illustrating a discharge door locking system coupled to the operating cylinder with a three way valve, according to a particular embodiment; 
         FIG. 8  is a block diagram illustrating a discharge door locking system coupled to the operating cylinder with a valve coupled to the lock piston, according to a particular embodiment; 
         FIG. 9  is a section view of a discharge door locking system for a mechanical lock, according to a particular embodiment; 
         FIG. 10  is a section view of a discharge door locking system for a mechanical lock in the locked position, according to a particular embodiment; 
         FIG. 11  is a section view of a discharge door locking system for a mechanical lock in the unlocked position, according to a particular embodiment; and 
         FIG. 12  is a flow diagram illustrating an example method of outfitting a railcar with a discharge door locking system, according to some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Rapid discharge railcars, such as hopper cars, may use air cylinders, operating beams, and linkages to operate bottom outlet doors. When the bottom outlet doors are closed, two features typically secure the doors. First, the linkages are in the over-center position. In the over-center position, the force from the weight of the lading on the doors pushes the operating beam and air cylinder toward the closed position. The second securement is a locking feature that prevents the beam, and therefore the air cylinder, from moving toward the open position. To open the doors, the locking feature needs to be released. Current locking features use a spring-loaded latch that must be mechanically pushed open as the air cylinder&#39;s piston extends to open the doors. Existing mechanical locks are dependent on timing and proper adjustment to operate efficiently. 
     Particular embodiments may provide improved door securement with less adjustment. Particular embodiments may include a pneumatically operated discharge door locking system that is automatically synchronized with the discharge door actuating system. 
     Particular embodiments are described with reference to  FIGS. 1-12  of the drawings. Like numbers may be used for like and corresponding parts of the various drawings. Various features of the embodiments will be described with respect to hopper car  20  shown in  FIGS. 1-4 . 
       FIG. 1  is a schematic drawing in elevation showing a side view of an example hopper car, according to a particular embodiment. Hopper car  20  may carry bulk materials such as coal and other types of lading. Examples of such lading may include sand, metal ores, aggregate, grain, ballast, etc. 
     Hopper car  20  may be generally described as a covered hopper car. However, other embodiments may include open hopper cars or any other cars suitable for carrying bulk lading. Hopper car  20  includes hoppers  22  with bottom discharge assemblies  24 . Discharge assemblies  24  may be opened and closed to control discharge of lading from hoppers  22 . As illustrated, hopper car  20  includes two hoppers  22 . In other embodiments, hopper car  20  may include one, two, three, or any suitable number of hoppers  22 . 
     In particular embodiments, hopper  22  is configured to carry bulk materials and the interior walls of hopper  22  are generally sloped towards discharge assembly  24  to facilitate discharge of the lading. Multiple hoppers  22  may be separated by interior bulkheads. 
     In particular embodiments, hopper car  20  may include a pair of sidewall assemblies  26  and sloped end wall assemblies  28  mounted on a railway car underframe. The railway car underframe includes center sill  34  and a pair of shear plates  32 . A pair of sill plates  32  provide support for sidewall assemblies  26 . 
     Center sill  34  is a structural element for carrying the loads of the hopper car. Center sill  34  transfers the various longitudinal forces encountered during train operation from car to car. Shear plates  30  extend generally parallel with center sill  34  and are spaced laterally from opposite sides of center sill  34 . 
     Hopper car  20  is an example of a rapid discharge railcar. Particular embodiments may include hopper cars, or any other type of rapid discharge railcar comprising discharge doors. 
       FIG. 2  is a schematic drawing in elevation showing an end view of an example hopper car, according to a particular embodiment.  FIG. 2  illustrates discharge assemblies  24 , end wall assemblies  28 , shear plates  30 , and sill plates  32  of hopper car  20  illustrated in  FIG. 1 . 
     Discharge assembly  24  comprises slope sheet  36 . Slope sheet  36  slopes from sidewall assembly  26  towards the center of hopper car  20  to facilitate discharge of the lading from the discharge opening of discharge assembly  24 . 
       FIG. 3  is a schematic drawing showing a cross section view of an example hopper car taken along lines B-B of  FIG. 1 .  FIG. 3  illustrates side wall assemblies  26 , shear plates  30 , sill plates  32 , and center sill  34  of hopper car  20  illustrated in  FIG. 1 . 
       FIG. 4  is a schematic perspective drawing illustrating longitudinal discharge doors underneath an example hopper car, according to a particular embodiment.  FIG. 4  illustrates in more detail the two discharge assemblies  24  illustrated in  FIG. 1 . Discharge assembly  24  includes operating beam  62 , discharge doors  64 , guides  66 , door struts  68 , and operating cylinder  70 . 
     Operating beam  62  is coupled to center sill  34  by guides  66 . Operating beam  62  is coupled to discharge door  64  by door struts  68 . Operating cylinder  70  is coupled to operating beam  62  and is operable to move operating beam  62  back and forth through guides  66 . 
     Operating beam  62  may comprise a steel box beam, may be extruded from aluminum or steel, may be pultruded as a fiber reinforced composite, such as a fiber or carbon composite, or any other suitable material. 
     Portions of slope sheet  36  cooperate with adjacent portions of center sill  34  to define longitudinal discharge openings. Longitudinal discharge openings are disposed along opposite sides of center sill  34 . 
     Discharge doors  64  are hinged proximate to center sill  34 . Various types of mechanical hinges may engage discharge doors  64  with center sill  34 . 
     Discharge doors  64  are illustrated in the closed position, which prevents the discharge of lading through the longitudinal discharge openings. In operation, operating cylinder  70  moves operating beam  62  through guides  66  to open discharge doors  64  via door struts  68 . 
     At a first end, door struts  68  are rotationally coupled to operating beam  62 . At a second end, door struts  68  are rotationally coupled to discharge door  64 . In particular embodiments, rotational coupling may be achieved via ball joints. 
     Operating cylinder  70  is operable to move operating beam  62  back and forth through guides  66 . In particular embodiments operating cylinder  70  may comprise a pneumatic cylinder, or any type of motor suitable for moving operating beam  62  in a longitudinal direction. 
     Longitudinal movement of operating beam  62  results in radial extension of door struts  68  to move discharge doors  64  from their open position to their closed position. Movement of operating beam  62  in the opposite direction results in pulling, pushing, or moving discharge doors from their closed position to their open position which allows rapid discharge of any lading contained within railway hopper car  20 . 
     In particular embodiments, each hopper  24  of hopper car  20  may be operated independently of each other. In other embodiments, each hopper  24  may be operated in unison by a single operating cylinder  70  and operating beam  62 . 
     Hopper car  20  may include a discharge door locking system. For example, to prevent accidental opening of discharge door  64 , such as during transit, a discharge door locking system may fasten operating beam  62  to a portion of the underframe. For example, a discharge door locking system may be mounted to center sill  34 , and may lock operating beam  62  to prevent operating beam  62  from moving. An example discharge door locking system is illustrated in  FIGS. 5A and 5B   
       FIG. 5A  is a block diagram illustrating a discharge door locking system in the unlocked position, according to a particular embodiment. Discharge door locking system  100  includes a lock cylinder, a lock piston, an extending input, and a retracting input. The lock cylinder may comprise lock air cylinder  74 . Lock air cylinder  74  houses lock piston  76 . Lock air cylinder  74  is operable to extend (see  FIG. 5B ) and retract ( FIG. 5A ) lock piston  76 . 
     Operating beam  62 , such as operating beam  62  described with respect to  FIG. 4 , comprises lock piston receiving recess  72 . Lock piston receiving recess  72  is configured to receive lock piston  76  when lock piston  76  is in the extended position. In some embodiments, lock piston receiving recess  72  may comprise a recess extending partially into operating beam  62  or completely through operating beam  62  (i.e., a hole in operating beam  62 ). 
     In particular embodiments, the extending input includes lock extending air line  78  and the retracting input includes lock retracting air line  80 . When compressed air is applied to lock extending air line  78 , lock piston  76  extends into lock piston receiving recess  72 , preventing operating beam  62  from moving. When compressed air is applied to lock retracting air line  80 , lock piston  76  retracts out of lock piston receiving recess  72 , permitting movement of operating beam  62 . 
       FIG. 5B  is a block diagram illustrating a discharge door locking system in the locked position, according to a particular embodiment. In  FIG. 5B , compressed air has been supplied to lock extending air line  78 . Lock piston  76  extends into lock piston receiving recess  72  and completely through operating beam  62 . Operating beam  62 , and thus discharge doors  64 , are locked in the closed position. 
       FIGS. 5A and 5B  illustrate a pneumatic discharge door locking system. Other embodiments may include electrical, hydraulic, or mechanical discharge door locking systems (e.g., the extending input and the retracting input may comprise electrical, hydraulic, and/or manual inputs). Some embodiments may include manual operation via a lever or cable. Some embodiments may include a combination. For example, some embodiments may pneumatically unlock the discharge door locking system, while using a spring or gravity to lock the discharge door locking system (see  FIGS. 6-11 ).  FIGS. 6-11  illustrate discharge door locking systems synchronized with the operating cylinder of the discharge door. 
       FIG. 6A  is a block diagram illustrating a discharge door locking system coupled to the operating cylinder with ball valves, according to a particular embodiment. Operating cylinder  70  is coupled to operating beam  62  via operating piston  90 . Operating cylinder  70  includes extending air line  86  (coupled to operating cylinder  70  behind operating piston  90 ) and retracting air line  88  (coupled to operating cylinder  70  in front of operating piston  90 ). 
     When compressed air is applied to extending air line  86 , operating beam  62  moves in a first direction opening discharge doors  64 . When compressed air is applied to retracting air line  88 , operating beam  62  moves in a second, opposite direction closing discharge doors  64 . Although a particular direction is illustrated, other embodiments may open or close discharge doors  64  by moving operating beam  62  in the opposite direction (e.g., push to open, pull to close; or, pull to open, push to close). 
     In particular embodiments, discharge door locking system  100  may be synchronized with the operation of operating cylinder  70 . For example, lock air cylinder  74  may be coupled to operating cylinder  70 . As a particular example, lock retracting air line  80  may be coupled to operating cylinder  70  (behind operating piston  90 ) via check valve  84   a . Lock extending air line  78  may be coupled to operating cylinder  70  (in front of operating piston  90 ) via check valve  84   b . Check valves  84   a  and  84   b  may comprise a pneumatic ball check valve, or any other suitable valve. 
     When compressed air is applied to extending air line  86 , compressed air also flows through check valve  84   a  to lock retracting air line  80 , which retracts lock piston  76  and permits operating beam  62  to move in a first direction opening discharge doors  64 . When compressed air is applied to retracting air line  88 , compressed air also flows through check valve  84   b  to lock extending air line  78 , which extends lock piston  76  into lock piston receiving recess  72  and prevents operating beam  62  from moving. Thus, operation of the discharge door locking system and the operating beam are synchronized. 
     In some embodiments, lock air cylinder may include spring  82 . In some embodiments, spring  82  may comprise a safety backup feature. For example, if air pressure is lost, spring  82  may keep lock piston  76  engaged with lock piston receiving recess  72 . 
     Other embodiments may include a hybrid pneumatic/mechanical system. For example, some embodiments may omit lock extending air line  78  (e.g., as illustrated in  FIG. 6B ). Lock piston  76  may be retracted pneumatically, and may be extended mechanically via spring, or any other suitable mechanism (mechanical, electrical, hydraulic, or otherwise). 
     Particular embodiments may synchronize discharge door locking system  100  with the operation of operating beam  62  in any suitable manner.  FIGS. 7 and 8  include additional examples. 
       FIG. 7  is a block diagram illustrating a discharge, door locking system coupled to the operating cylinder with a three way valve, according to a particular embodiment, Discharge door locking system  100  may be synchronized with the operation of operating cylinder  70  similar to the embodiment described with respect to  FIG. 6A , except that compressed air may be applied to both operating cylinder  70  and lock air cylinder  74  via 3-way valves  92   a  and  92   b.    
     In particular embodiments, 3-way valve  92   a  may direct compressed air to lock retracting air line  80  and extending air line  86 . 3-way valve  92   b  may direct compressed air to lock extending air line  78  and retracting air line  88 . Thus, operating cylinder  70  and lock air cylinder  74  may be operated at the same time. 
       FIG. 8  is a block diagram illustrating a discharge door locking system coupled to the operating cylinder with a valve coupled to the lock piston. Similar to  FIGS. 4-7 , operating cylinder  70  facilitates movement of operating beam  62 . Operating cylinder  70  is coupled to operating beam  62  via operating piston  90 . Operating cylinder  70  includes extending air line  86  and retracting air line  88 . When compressed air is applied to extending air line  86 , operating beam  62  moves in a first direction opening discharge doors  64 . When compressed air is applied to retracting air line  88 , operating beam  62  moves in a second, opposite direction closing discharge doors  64 . 
     Lock air cylinder  74  facilitates movement of lock piston  76 . For example, lock extending air line  78  supplies compressed air to lock air cylinder  74  to extend lock piston  76 . Lock retracting air line  80  supplies compressed air to lock air cylinder  74  to retract lock piston  76 . 
     In particular embodiments, discharge door locking system  100  may be synchronized with the operation of operating cylinder  70 . For example, lock air cylinder  74  may be coupled to operating cylinder actuating valve  96 . Operating cylinder actuating valve  96  controls operating cylinder  70  by supplying compressed air to either the extending or retracting inputs of operating cylinder  70 . 
     Operating cylinder actuating valve  96  includes operating cylinder air line  98 . Operating cylinder air line  98  provides compressed air for operating cylinder  70 . For example, in a first position operating cylinder actuating valve  96  supplies compressed air from operating cylinder air line  98  to extending air line  86 . In a second position, operating cylinder actuating valve  96  supplies compressed air from operating cylinder air line  98  to retracting air line  88 . Thus, operating cylinder actuating valve  96  controls operating cylinder  70  by switching compressed air from operating cylinder air line  98  to either extending air line  86  or retracting air line  88 . 
     Operating cylinder actuating valve  96  may be controlled by lock piston  76 . For example, lock piston  76  may be coupled to operating cylinder actuating valve  96 . Movement of lock piston  76  from the retracted to extended position, and vice versa, may switch operating cylinder actuating valve  96  from a first position to a second position. 
     For example, when compressed air is supplied to lock retracting air line  80 , compressed air flows through retracting air line  80  and retracts lock piston  76 . Lock piston  76  may switch operating cylinder actuating valve  96  to a first position so that operating cylinder actuating valve  96  supplies compressed air from operating cylinder air line  98  to extending air line  86  which extends operating beam  62  in a first direction to open discharge doors  64 . When compressed air is supplied to lock extending air line  78 , compressed air flows through extending air line  78  and extends lock piston  76 . Lock piston  76  may switch operating cylinder actuating valve  96  to a first position so that operating cylinder actuating valve  96  supplies compressed air from operating cylinder air line  98  to extending air line  86  which retracts operating beam  62  in a second direction to close discharge doors  64 . 
     As operating beam  62  closes discharge doors  64 , lock piston  76  engages into lock piston receiving recess  72 , which prevents operating beam  62  from moving. Thus, operation of the discharge door locking system and the operating beam are synchronized. 
     In some embodiments, lock air cylinder may include spring  82 . In some embodiments, spring  82  may comprise a safety backup feature. For example, if air pressure is lost, spring  82  may keep lock piston  76  engaged with lock piston receiving recess  72 . 
     A particular advantage of the illustrated embodiment is that if the lock mechanism is not disengaged (i.e., lock piston  76  is not retracted) the operating cylinder will not receive air pressure (e.g., lock piston  76  will not actuate operating cylinder actuating valve  96 ). Thus, the operating cylinder is not able to move the operating beam while the operating beam is locked. This prevents excessive loading and wear on components. 
     Other embodiments may include a hybrid pneumatic/mechanical system. For example, some embodiments may omit lock extending air line  78 . Lock piston  76  may be retracted pneumatically, and may be extended mechanically via spring, or any other suitable mechanism (mechanical, electrical, hydraulic, or otherwise). 
     Some embodiments may include a pneumatic discharge door locking system in conjunction with a mechanical operating beam lock. An example is illustrated in  FIG. 9 . 
       FIG. 9  is a section view of a discharge door locking system for a mechanical lock, according to a particular embodiment. The section view is along the longitudinal centerline of the operating beam. Similar to  FIGS. 4-8 , operating cylinder  70  is coupled to operating beam  62  via operating piston  90 . Operating cylinder  70  moves operating beam  62  in a first direction to open discharge doors  64 , and moves operating beam  62  in a second, opposite direction to close discharge doors  64 . In the illustrated embodiment, operating beam  62  moves right and left. 
     The example embodiment includes a mechanical operating beam lock. The mechanical operating beam lock includes locking latch  102 , lock cam  104 , locking latch pivot  106 , and locking rod  108 . Locking latch  102  pivots up and down on locking latch pivot  106 . Locking rod  108  is coupled to operating beam  62 . In the down position, locking latch  102  partially surrounds locking rod  108 , preventing operating beam  62  from moving. In the up position, locking latch  102  does not contact locking rod  108 , and operating beam  62  is free to move back and forth. 
     Operating piston  90  is coupled to operating beam  62  via lock cam  104 . Lock cam  104  comprises a protrusion that lifts locking latch  102  as lock cam  104  moves to the right in the figure and lowers locking latch  102  as lock cam  104  moves to the left in the figure. For example, as operating cylinder  70  extends operating piston  90  to open discharge doors  64 , lock cam  104  moves to the right, which causes the protrusion of lock cam  104  to lift locking latch  102  and unlocks operating beam  62 . As operating cylinder  70  retracts operating piston  90  to close discharge doors  64 , lock cam  104  moves to the left, which lowers locking latch  102  onto lock rod  108  and locks operating beam  62 . 
     Lock cam  104  is coupled to operating beam  62  via lock cam pin  110  and elongated hole  112 . Lock cam  104  includes elongated hole  112 . Lock cam pin  110  is coupled to operating beam  62  through elongated hole  112 . The width of elongated hole  112  is wider than lock cam pin  110 . Lock cam pin  110  may move the width of elongated hole  112  before operating beam  62  moves. Thus, elongated hole  112  enables lock cam  104  to unlock locking latch  102  before operating beam  62  begins to move, and enables lock cam  103  to lock locking latch  102  after operating beam  62  has stopped moving. 
     For example, as operating cylinder  70  extends operating piston  90 , lock cam  104  moves to the right for the width of elongated hole  112  before lock cam pin  110  contacts the other side of elongated hole  112  and causes operating beam  62  to move. The initial movement of lock cam  104  is enough for the protrusion of lock cam  104  to unlock locking latch  102  before operating beam  62  begins to move. Similarly, elongated hole  112  and stop bracket  126  enable lock cam  103  to lock locking latch  102  after operating beam  62  has stopped moving. 
     Stop bracket  126  is a mechanical stop that prevents operating beam  62  from moving any further in the direction towards operating cylinder  70 . Stop bracket  126  is coupled to center sill  34 . Stop bracket  126  may comprise a steel bracket welded to center sill  34 . 
     As operating cylinder  70  retracts operating piston  90 , operating beam  62  contacts stop bracket  126  which causes operating beam  62  to stop moving. After operating beam  62  stops moving, lock cam  104  continues moving to the left for the width of elongated hole  112 . The additional movement of lock cam pin  110  lets locking latch  102  drop onto locking rod  108  after operating beam  62  has stopped moving. Locking latch  102  may drop onto locking rod  108  via gravity or with the assistance of springs. 
     A particular advantage of some embodiments is to prevent accidental unlocking by using a lock block that physically prevents the mechanical operating beam lock from unlocking. Lock block  114  is coupled to center sill  34  via bracket  118 . When hopper car  20  is in motion, lock block  114  is positioned above locking latch  102 , preventing locking latch  102  from lifting up. Lock block  114  may comprise steel, rubber, plastic, or any other suitable material. 
     Lock block  114  is also slidably coupled to track  116 . Lock block  114  may slide from a first position over locking latch  102 , and obstructing upward movement of locking latch  102 , to a second position that does not obstruct the movement of locking latch  102 . When lock block  114  is in the second position, locking latch  102  may be lifted up to unlock operating beam  62 . 
     Lock block  114  includes cylinder mount  20 . Cylinder mount  20  couples lock block  114  to a lock operating cylinder, such as lock operating cylinder  122  illustrated in  FIGS. 10 and 11 . 
       FIG. 10  is a section view of a discharge door locking system for a mechanical lock in the locked position, according to a particular embodiment. The section view is along a transverse line through hopper car  20  illustrating lock block  114  as described with respect to  FIG. 9 . 
     Lock operating cylinder  122  is coupled to lock block  114  via cylinder mount  20 . Lock operating cylinder  122  is operable to move lock block  114  along track  116 . When hopper car  20  is in motion, lock operating cylinder  122  retracts and lock block  114  is in the first position (as illustrated) preventing locking latch  102  from moving.  FIG. 11  illustrates lock block  114  in the second, unlocked position. 
       FIG. 11  is a section view of a discharge door locking system for a mechanical lock in the unlocked position, according to a particular embodiment. The section view is the same as  FIG. 10 . 
     When hopper car  20  is stopped, operating cylinder  122  extends which moves lock block  114  to the second position (as illustrated), enabling locking latch  102  to be lifted up to the unlocked position. 
     In particular embodiments, the discharge door locking system may be synchronized with the operation of operating cylinder  70 . For example, lock operating cylinder  122  may include air inlet  124 . When lock operating cylinder  122  receives compressed air via air inlet  124 , the compressed air causes lock operating cylinder  122  to extend and move lock block  114  to the second position. When lock block  114  is in the second position, operating cylinder  70  may be activated to open or close discharge doors  64 . Lock operating cylinder  122  also includes one or more springs that return lock operating cylinder  122  to the retracted position when compressed air is removed from air inlet  124 . 
     In particular embodiments, air inlet  124  receives compressed air whenever hopper car  20  is connected to a compressed air source. For example, when hopper car  20  is in a rail yard and a rail operator connects hopper car  20  to a compressed air source, lock operating cylinder  122  is automatically extended to move lock block  114  to the second position. Then, the rail operator may activate or deactivate operating cylinder  70  using the separate pneumatic controls for operating cylinder  70 . When the rail operator disconnects hopper car  20  from a compressed air source, lock operating cylinder automatically retracts to move lock block  114  to the first position. Thus, when rail car  20  is connected to a compressed air source, an operator is free to open and close discharge doors  64 . When rail car  20  is disconnected from the compressed air source (e.g., in transit) discharge doors  64  are locked. 
       FIG. 12  is a flow diagram illustrating an example method of outfitting a railcar with a discharge door locking system, according to some embodiments. In particular embodiments, one or more steps of  FIG. 12  may be performed to outfit hopper car  20  with discharge door locking system  100 , described with respect to  FIGS. 1-11 . 
     The method begins at step  1212 , where a railcar is provided. The railcar comprises an underframe, a hopper coupled to the underframe, a discharge door coupled to the hopper proximate the underframe, and an operating beam coupled to the discharge door and the underframe. 
     In some embodiments, the operating beam comprises a lock piston receiving recess. The railcar further comprises an operating cylinder coupled to the operating beam. The operating cylinder comprises a first input and a second input. The operating cylinder is configured to move the operating beam between a first position where the discharge door is in a closed position and a second position where the discharge door is in an open position. Activation of the first input causes the operating cylinder to move the operating beam to the first position, and activation of the second input causes the operating cylinder to move the operating beam to the second position. 
     In some embodiments, the operating cylinder is coupled to the operating beam with a mechanical operating beam lock. In these embodiments, the operating beam may not include a lock piston receiving recess. 
     For example, step  1212  may comprise providing hopper car  20  as described with respect to any of  FIGS. 1-11 . In particular embodiments, the railcar may be a new railcar under construction, or the railcar may be an existing railcar to be retrofitted with a discharge door locking system. 
     At step  1214 , a discharge door locking system is coupled to the underframe of the railcar. In some embodiments, the discharge door locking system comprises a lock piston, a first input, and a second input. The discharge door locking system may be configured to move the lock piston between a first position where the lock piston is not engaged with the lock piston receiving recess and a second position where the lock piston is engaged with the lock piston receiving recess. Activation of the first input moves the lock piston to the first position, and activation of the second input moves the lock piston to the second position. 
     For example, discharge door locking system  100  may be coupled to an underframe of hopper car  20 . Discharge door locking system  100  may be coupled to center sill  34 , or any other suitable mounting location on hopper car  20 . Discharge door locking system  100  may be positioned so that lock piston  76  may engage with lock piston receiving recess  72  of operating beam  62  when lock piston  76  is in the extended position. 
     In some embodiments, the discharge door locking system may comprise a lock block slidably coupled to the underframe. The lock block may be configured to move between a first position where the lock block prevents the mechanical operating beam lock from moving to the unlocked position and a second position where the lock block does not prevent the mechanical operating beam lock from moving to the unlocked position. For example, discharge door locking system  100  may comprise lock block  114  slidably coupled to center sill  34  via bracket  118  and track  116 . 
     At step  1216 , the inputs of the discharge door locking system are coupled to the inputs of the operating cylinder. In particular embodiments, the second input of the operating cylinder may be coupled to the first input of the discharge door locking system. The first input of the operating cylinder may be coupled to the second input of the discharge door locking system. When the second input of the operating cylinder is activated to move the discharge door to the open position, the first input of the discharge door locking system is also activated to disengage the lock piston from the lock piston receiving recess. When the first input of the operating cylinder is activated to move the discharge door to the closed position, the second input of the discharge door locking system is also activated to engage the lock piston with the lock piston receiving recess. 
     In particular embodiments, the discharge door locking system includes an operating cylinder actuating valve coupled to the lock piston, the first input of the operating cylinder, and the second input of the operating cylinder. Coupling the inputs of the discharge door locking system to the inputs of the operating cylinder may include coupling the first and second input of the operating cylinder to the operating cylinder actuating valve. When the lock piston is in the first position, the operating cylinder actuating valve is configured to activate the second input of the operating cylinder to move the discharge door to the open position. When the lock piston is in the second position, the operating cylinder actuating valve is configured to activate the first input of the operating cylinder to move the discharge door to the closed position. 
     In some embodiments, the discharge door locking system includes a lock block and a lock operating cylinder with an air inlet. The air inlet of the lock operating cylinder and the first and second inputs of the operating cylinder may be coupled to a compressed air source. When the air inlet of the lock operating cylinder is coupled to the compressed air source, the lock block automatically slides to an unlocked position. The first and second inputs of the operating cylinder may be used to open or close the discharge doors. When the air inlet of the lock operating cylinder is decoupled from the compressed air source, the lock block automatically slides to a locked position. 
     For example, discharge door locking system  100  may be synchronized with the operation of operating cylinder  70  by coupling lock air cylinder  74  to operating cylinder  70 . Lock air cylinder  74  may be coupled to operating cylinder  70  according to any of the examples described with respect to  FIGS. 5A-11 . 
     In a retrofit application, for example, a 3-way valve may be added to the two air inputs to operating cylinder  70  to provide compressed air to the two inputs of lock air cylinder  74 . In another example, outlet ports may be added to operating cylinder  70 , which may be used in conjunction with ball valves to provide compressed air to the inputs of lock air cylinder  74 . 
     In another retrofit example, the two air inputs of operating cylinder  70  may be coupled to an operating cylinder actuating valve. The operating cylinder actuating valve may also be coupled to lock air cylinder  74  such that the position of lock piston  76  controls the operating cylinder actuating valve. 
     In another retrofit example, lock block  114  may be slidably coupled to the center sill directly above a mechanical operating beam lock. Lock block  114  prevents the mechanical operating beam lock when hopper car  20  is in transit, and automatically slides out of the way of the mechanical operating beam lock when compressed air is applied to hopper car  20 . 
     Modifications, additions, or omissions may be made to method  1200 . Additionally, one or more steps in method  1200  of  FIG. 12  may be performed in parallel or in any suitable order. 
     Although the components in  FIGS. 1-12  are described with respect to longitudinal doors, particular embodiments may include transverse doors, or any other suitable discharge door of a railcar. 
     Although particular embodiments and their advantages have been described in detail, it should be understood that various changes, substitutions and alternations can be made herein without departing from the spirit and scope of the embodiments.