Abstract:
The disclosed jack assembly is used to raise the frame of a railroad car to a sufficient height above a wheeled truck assembly coupled to the railroad car in order to perform maintenance or remove the truck assembly. The jack assembly comprises an air-operated bellows which raises and lowers a plate that engages the railroad car for the raising and lowering action. Telescoping posts and other support members aid in stabilizing the jack assembly during use in order to prevent failure of the bellows due to buckling under the weight of the railroad car. The jack assembly is readily mobile between locations, and can be operated by a single user.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to the field of lifting devices, and more particularly to a railroad car jack assembly.  
         BACKGROUND OF THE INVENTION  
         [0002]    A typical railroad car has an elongated frame and a pair of wheeled truck assemblies attached to the frame. Each truck assembly is attached to the frame at each end of the car. Each wheeled truck assembly in turn includes flanged wheels that are adapted to roll on a pair of railroad track rails.  
           [0003]    With the wheels on the track rails, there may be clearance of only a few inches between the top of the railroad track rails and the underside of the railroad car frame. Routine maintenance may require that the car frame be elevated somewhat in order to increase this clearance. One form of maintenance may require that the railroad car be completely removed from one of the truck assemblies, to allow such truck assembly to be replaced with another. For example, to remove the assembly, the one end of the car may be lifted vertically about 10-25 inches, while the other end of the car remains supported on the other wheeled truck assembly. With the one car end so elevated, both the old and the new truck assemblies can be rolled along the rails. Other forms of maintenance may require a worker to crawl about beneath the car, and this increased clearance would also be beneficial.  
           [0004]    One way of lifting one end of the railroad car is by means of a crane. This is done by connecting the lift line of the crane to the car frame, such as at the car coupling. This requires the presence of a high capacity crane that can carry the load of the car, and such a crane will typically be quite large and represent a significant capital investment. Moreover, such a crane may be mounted on a special railroad service car or road vehicle. If the crane limited to rolling along on track rails, it may not be conveniently moved from one site to another. If the crane is on a road vehicle, the crane may be used only at certain rail sites because of its size.  
           [0005]    Another way the railroad car can be removed from the wheeled truck assembly is by means of a pair of separate lift jacks, interposed between the underlying rail bed and each side of the car frame. These jacks are relatively inexpensive, and quite portable. However, as the separate jacks bear against the rail bed, special shoring efforts may be needed in order to provide added stability to the jacks and to prevent the jacks from sinking into the rail bed. Moreover, with the jacks on opposite sides of the car, several people may be needed to operate the jacks.  
           [0006]    Moreover, there are certain inherent risks with the use of either the crane or paired lift jacks because they bear the entire load of the railroad car during the time the wheeled truck is removed from the car or while someone is under the car for servicing. A crosswind may cause the crane-suspended car to sway, or the paired jack-supported car may topple sideways off of the jacks. This can be both dangerous to personnel and destructive to property. Dangerously, any failure of the crane lift line or of either jack can allow the raised car to fall.  
           [0007]    U.S. Pat. No. 4,805,875 (“the &#39;875 patent”) discloses a prior art railroad car jack assembly. This patent discloses a pair of rails and a multi-tiered cylindrical power lift system attached to a plate that engages and lifts the railroad car. The &#39;875 patent also discloses a pair of side block bars that engage the railroad car engaging plate after the plate has raised the railroad car. The block bars provide added support to the car when the engaging plate is at the top of the operative range of movement. Both the power lift system and the block bars are actuated by a hydraulic fluid pumping system.  
           [0008]    Although providing a substantial improvement over the prior art, the railroad car jack assembly in the &#39;875 patent has some shortcomings, however. For example, the hydraulic pump system used is expensive, heavy and often requires significant maintenance. Also, the hydraulic lift system is raised and lowered in a somewhat long period of time.  
           [0009]    Another prior art jack assembly, U.S. Pat. No. 1,745,959, provides a pair of telescoping posts to support the car engaging means so as to prevent the lifting means from buckling and tipping. While a pair of posts can prevent some angular rotation of the car engaging means, it generally acts to prevent such movement in a limited fashion.  
           [0010]    The present invention is directed to an improved portable jack assembly that overcomes one or more of the drawbacks as set forth above.  
         BRIEF SUMMARY OF THE INVENTION  
         [0011]    One aspect of the present invention provides a jack assembly that is self contained and relatively lightweight, to be quite portable to different use sites. The disclosed jack assembly may also be operated by one person at almost any rail site.  
           [0012]    Another aspect of the present invention provides that the disclosed jack assembly cooperates directly between the track rails and the car frame, providing safe non-yielding, solid metal-to-metal, triangulated support of the railroad car above the track rails, and without the need of braces or supports to be placed on the rail bed surface.  
           [0013]    The present invention may consist of a jack assembly having an elongated structural frame member of sufficient length to span between and beyond the spaced railroad track rails to support a railroad car. An air-powered lift means is connected to the frame member, operating a car engaging means that may be moved in a normal direction with respect to the frame member and the track rails. When in a contracted position, the frame member, power lift means and car engaging means have a clearance under the railroad car sufficient to be manipulated into useable position. When in an extended position, the assembly elevates the car engaging means initially against the underside of the railroad car and then lifts the car vertically so as to separate the railroad car from a wheeled truck assembly.  
           [0014]    A further embodiment may include a plurality of telescoping posts surrounding the power lift means to provide lateral support while raising and lower the car engaging means. The posts also provide rotational support for the car engaging means, thereby keeping the car engaging means substantially parallel to the frame members.  
           [0015]    Another embodiment may include rotating support members that provide additional support to the power lift means. The support members have an abutting relationship with the car engaging means when the power lift means is fully extended to help distribute the load of the railroad car and provide lateral and rotational stability. Air cylinders can be used to actuate the support members between a lowered position and a raised position.  
           [0016]    An air source used to activate the power lift means may be mounted as a unitary part of the jack assembly or may be physically separated from the jack assembly, provided there is an operative connection therebetween.  
           [0017]    In another embodiment, a method of raising a railroad car is provided. The method comprising the steps of providing a pair of frame members, a power lift means attached to the frame members, a railroad car engaging means and an air source to activate the power lift means. Air pressure from the air source is introduced to the power lift means to extend the power lift means, thereby raising the car engaging means in a vertical direction. Posts are placed around the power lift means and attached to the car engaging means so as to provide lateral and rotational support while raising and lowering the railroad car.  
           [0018]    The drawings and detailed description disclose the preferred embodiments in greater detail, along with many of their advantages. 
       
    
    
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS  
       [0019]    [0019]FIG. 1 is a top view of a railroad car, partly broken away for clarity, illustrating one embodiment of the present invention;  
         [0020]    [0020]FIG. 2 is a side view of the car and jack assembly illustrated in FIG. 1;  
         [0021]    [0021]FIG. 3 is an enlarged sectional view, as taken generally from line  3 - 3  in FIG. 2;  
         [0022]    [0022]FIG. 4 is a top view of the jack assembly of FIG. 3, with the railroad car eliminated for clarity;  
         [0023]    [0023]FIG. 5 is an enlarged side view similar to FIG. 3, illustrating a portion of the jack assembly;  
         [0024]    [0024]FIG. 6 is a top view of that portion of the jack assembly illustrated in FIG. 5; and  
         [0025]    [0025]FIG. 7 is a sectional view, as taken generally from line  7 - 7  in FIG. 5. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0026]    [0026]FIG. 1 is a top view of the railroad car jack  34  in a preferred operative position beneath a railroad car  20 . A section of railroad car flooring  33  has been cut away to show the location of a wheeled truck assembly  26  with respect to the railroad car frame  24  and the railroad track rails  22 .  
         [0027]    In a first embodiment, a flat-bed railroad car  20 , as illustrated in FIGS. 1, 2 and  3 , has flanged wheels  21  adapted to roll on two laterally spaced track rails  22 . The railroad car  20  has a frame  24  including a central sill  23  and side channels  25 , each elongated in the direction of the track rails  22 . A wheeled truck assembly  26  is connected to the central sill  23  of the frame  24  at each end of the railroad car  20 . Couplings  28  are connected to the frame  24  at the opposite ends of the car  20 .  
         [0028]    Each wheeled truck assembly  26  includes a cross member  30  and a pair of side frame members  31 . The cross member  30  is coupled at its ends through spring and snubbing means (not shown) to the side frame members  31 . One flanged wheel  21  is fixed adjacent each end of axle  32 , and two such axles  32  are mounted in bearings (not shown) carried in the opposite respective side frames  31 .  
         [0029]    A typical railroad car may be approximately ten feet wide, across the exterior of its side sections  25  or flooring  33 . The railroad car  20  rides centered relative the track rails  22 , which conventionally may be separated by approximately four and one-half feet. With the wheels  21  on the track rails  22 , there may be only about 10 inches of vertical clearance between the tops of the track rails  22  and the underside of the railroad car frame  24  at the central sill  23 .  
         [0030]    The jack assembly  34 , to be discussed further herein, may be used to lift the railroad car frame  24 . For example, the railroad car frame  24  may be lifted completely off of a single wheeled truck assembly  26  as shown in FIG. 2. The jack assembly  34  is placed between the wheeled truck assemblies  26 , usually closer to one wheeled truck assembly  26  while still being able to engage the central sill  23  of the frame  24 . The operative position of the jack assembly  34  is preferably where the car engaging means  40  can engage the central sill  23 , and where the central sill  23  is substantially parallel to the underlying track rails  22 . In the operative position, the car engaging means  40  can engage the frame  24  and lift the frame  24  to a position spaced above the wheeled truck assembly  26  while the frame  24  remains supported on the opposite wheeled truck assembly  26 . Each wheeled truck assembly  26  is self-contained, and can be easily connected to or separated from the railroad car  20 . A stop  41  on the frame members  56  may be used to engage one of the track rails  22  so that the car engaging means  40  of the jack assembly  34  is centered relative to the track rails  22  and relative to the central sill  23 . A foot  75  can be attached to the end of the frame members  56  to be set adjustably in a vertical direction to a firmed position against the underlying rail bed surface  76  and locked as adjusted. The foot  75  stabilizes the jack assembly  34  before, during and after the railroad car  20  is lifted.  
         [0031]    As illustrated in FIGS. 4-7, the frame members  56  can be formed of two structural I-beams  77  held substantially parallel by laterally spaced apart end angles  78  and  79 , a base plate  80 , and cross members  90  and  91 , each welded or otherwise secured to and between the I-beams  77 . The lead end angle  78  may be oriented with its separate legs angled at 45 degrees relative to the beam, so that the inclined lower leg may help ride the suspended remote end of the frame members  56  onto the remote track rail  22 , as the jack assembly  24  is being positioned from the opposite car side  55 .  
         [0032]    The pair of elongated frame members  56  are of a length sufficient to span between and beyond the track rails  22 , and of sufficient strength, when spanned between the rails, to carry the load of the elevated railroad car  20 . The base plate  80  is coupled to the bottom inward-facing flange of the I-beams  77 .  
         [0033]    A power lift means  38 , illustrated as inflatable-deflatable bellows, is attached between the base plate  80  and a car engaging means  40 . The power lift means  38  includes several toroidal-like sections that create a continuous generally cylindrical chamber. The car engaging means  40  is adapted to be moved by the power lift means  38  in a normal direction, toward or away from the frame members  56  and track rails  22 .  
         [0034]    The power lift means  38  can be adapted to receive an air line  50  in which pressurized air is introduced into the chamber. The bellows of the power lift means  38  are collapsible as the car engaging means  40  is lowered from a fully extended position. The chamber wall of the power lift means  38  is about one-half (½) inch thick, a sufficient thickness to withstand a maximum pressure within the chamber of about 125 psi. In the preferred embodiment, the bellows  38  is made of fiber-reinforced rubber, such as those produced by Firestone under the name AIRSTROKE® and Model No. 348-3 for industrial applications. Because of the flexibility of the power lift means  38  in a fully extended position, the car engaging means  40  would tend to slip thereby causing the power lift means  38  to buckle. Additional stabilizing means can be used to prevent the power lift means  38  from buckling. One skilled in the art can appreciate that the power lift means  38  can be made of a single bellows, multiple bellows, an airbag, or any type of air-filled structure sufficient to raise the car engaging means  40 . It can also be appreciated by one skilled in the arts that such air-filled structures can be made of fabric, polymeric material, or any other material of sufficient strength to withstand the internal pressure during the lifting process.  
         [0035]    In the preferred embodiment, the car engaging means  40  is a generally square steel plate. The dimensions of the car engaging means  40  is about 52 ft by 42 ft by 1 inch. When the power lift means  38  is in the collapsed position, the car engaging means  40  rests atop the frame members  56 . One skilled in the art can appreciate that the car engaging means  40  can be made of any material sufficient to carry the load of a railroad car  20 .  
         [0036]    The power lift means  38  has a collar  109  that connects the power lift means  38  to the base plate  80  in an airtight manner. A collar  110  also connects the power lift means  38  to the car engaging means  40 , thereby forming a seal at both ends of the power lift means  38 . The base plate  80  is secured to the I-beams  77  by nut and bolt means  111 .  
         [0037]    A plurality of posts  60  are positioned surrounding the power lift means  38 . The posts  60  are attached at the top to the car engaging means  40 , and at the bottom to the base plate  80 . The posts  60 , illustrated as telescoping posts, provide lateral and rotational support to the car engaging means  40 . The posts  60  follow the action of the car engaging means  40 . In other words, the posts  60  extend when the car engaging means  40  is raised, and the posts  60  contract when the power lift plate is lowered. The posts  60  help stabilize the power lift means  38  as it is inflated and deflated to prevent the buckling as previously described.  
         [0038]    In a preferred embodiment, four telescoping posts  60  are rigidly connected to the car engaging means  40  to help prevent buckling or sliding of the power lift means  38 . The telescoping posts  60  are hollow concentric cylinders that slide vertically with respect to each other. The smallest inner cylinder attached to the car engaging means  40  and the largest outer cylinder attached to the base plate  80 . The cylinders of the posts  60  are preferably made of steel. The largest cylinder of the posts  60  can have an outside diameter of about 6 inches, and a wall thickness of about one-half (½) inches. The smallest cylinder of the posts  60  can have an outside diameter of about two and a half (2½) inches, and a wall thickness of about one-quarter (¼) inches. One skilled in the art can appreciate that the posts can be made of a material of sufficient strength and rigidity to withstand the loads tending to cause rotational movement of the car engaging means  40 .  
         [0039]    As the car engaging means  40  is raised, each section of the telescoping posts  60  can slide relative to each other. Sufficient lubrication is provided to allow such a sliding motion. In a further embodiment, as the car engaging means  40  is raised, the smallest cylinder of the post  60  is extended fully before the next smallest cylinder can be extended. In another embodiment, all the cylinders of the posts  60  are free to extend and contract with respect to each other. Other structures that can be used to provide stability for the power lift means  38  while the car engaging means  40  is raised and lowered include: collapsible rails, scissor-like linkages, square tubing, rods, or hollow tubes. One skilled in the art can appreciate structures that can provide lateral and rotational stability to the power lift means  38 .  
         [0040]    A pair of rigid, panel-like support members  61  are positioned relative to the frame members  56 , and are adapted to be pivoted about journals  62  between a raised position (illustrated in solid in FIG. 5) abutting stops  64  on the underside of the car engaging means  40 , and a lowered position (illustrated in phantom in FIG. 5) aligned substantially parallel with the frame members  56 . The support members  61 , when in the raised position, provide a solid brace for supporting the car engaging means  40  and railroad car  20 . This feature is effective as a safety device even in the event of failure of the power lift means  38 . The journals  62  are rigidly connected to a cross member  91 .  
         [0041]    The support members  61  can be moved between the raised and lowered position by at least one power cylinder  65 . Each power cylinder  65  is rotationally attached to a cross member  90  and a support member  61 . In the preferred embodiment, each support member  61  is actuated by a pair of power cylinders  65 . In the preferred embodiment, the power cylinders  65  are gas-powered struts.  
         [0042]    A compressed-air delivery system  42  for activating the power lift means  38  and the power cylinders  65  is provided. The compressed-air delivery system  42  can include a compressor  43 , control valves  44  and  46 , and appropriate lines to connect these components to the power cylinders  65  and the power lift means  38 . A handle  53  may be used to shift the control valves  44  and  46  between their operative positions. An internal combustion engine  54  may be used to drive the compressor  43 . In the alternative, an electric or battery-powered motor can be used. Other types of pumping or air-delivery systems known in the art may be implemented. The components of the compressed-air delivery system  42  may be located laterally outside of or beyond one side  55  of the railroad car  20 , and carried as a unitary part of the jack assembly  34 . The control handle  53  may also be laterally beyond the side  55  of the railroad car  20 , to be conveniently reached and shifted by someone standing at this location.  
         [0043]    Each support member  61  is formed of a shaft  86  rotated within journals  62 , and spaced arms  87  welded to the shaft  86 . A face member  89 , with a cambered edge to abut the car engaging means  40 , is welded to and between the arms  87 . The support member arms  87  are located laterally between the separate frame members  56 , and the journals  62  are secured to a cross members  91 . The cambered edge of the face member  89  is preferred, because it allows for a more stable connection between the face member  89  and the car engaging means  40 . The cambered edge will abut the car engaging means  40 , regardless of any possible angular rotation of the car engaging means  40 .  
         [0044]    The support member journals  62  are located laterally beyond the stops  64  of the car engaging means  40  and are generally evenly spaced therefrom. The support members  61  rotate upwardly about the journals  62  toward the stops  64  until the camber edge of the face member  89  abuts the car engaging means  40 . This configuration mechanically locks the support members  61  in a raised bracing position against the car engaging means  40  and stops  64 , independent of continued urging by the power cylinders  65  of the face members  89  against the stops  64 . Thus, once the support members  61  are set in place, the jack assembly  34  may be supported by the support members  61  even without any pressure in either the power lift means  38  or the power cylinders  65 .  
         [0045]    The power cylinders  65  can be activated by the compressed-air delivery system  42  at the same time that the power lift means  38  is activated. Thus, as the power lift means  38  is being inflated, the support members  61  are being raised simultaneously. Final positioning occurs after the car engaging means  40  has reached full height. In an alternate embodiment, the power cylinders  65  can be activated after the power lift means  38  has been fully extended. Thus, once the railroad car frame  24  has been lifted above the wheeled truck assembly  26 , the support members  61  are then raised to abut the car engaging means  40 . In a further embodiment, there can be sensors that activate the power cylinders  65  once the car engaging means  40  reaches a predetermined height. The predetermined height can be measured either by the distance between the frame members  56  and the car engaging means  40 , the distance between the railroad car frame  24  and the wheeled truck assembly  26 , or any other measurement sufficient to remove or repair a wheeled truck assembly  26 . It can be appreciated by those skilled in the art that the support members  61  can be rotated between a lowered and a raised position at different rates of angular rotation and the power cylinders  65  can be activated at any time during the raising and lower of the car engaging means  40 .  
         [0046]    The car engaging means  40  and the posts  60  are rigidly connected to the top surface of the power lift means  38 . This allows the overlying frame  24  of the railroad car  20  to fit generally flat against the car engaging means  40  for effective load distribution. As the car engaging means  40  lifts the car frame  24 , the weight of the railroad car  20  may urge the car engaging means  40  to rotate if it is not centrally positioned under the car or if the car has an uneven weight distribution. In other words, one edge of the car engaging means  40  may tend toward the ground while the opposing end tends away from the ground. This angular rotation of the car engaging means  40  is prevented by the rigid connection between the posts  60  and the car engaging means  40 . Thus, the car engaging means  40  remains substantially parallel to the frame members  56 . Due to the tremendous weight of a typical railroad car  20 , it becomes important to surround the power lift means  38  with the posts  60 .  
         [0047]    A pressure line  50  is connected between the compressor  43  and an opening fluidly connected to the power lift means  38 . Pressurized air is admitted to the chamber of the bellows  38  via line  50 , actuating the power lift means  38  axially to an expanded configuration. Air pressure lines  48  connect the compressor  43  to the power cylinders  65  to actuate the support members  61  between the lowered and raised positions. Air or pressure regulators may also be installed so the bellows of the power lift means  38  is not damaged by over-inflation.  
         [0048]    The compressed-air delivery system  42  is activated by moving the handle  53  between various positions. In the first position, the compressed-air delivery system  42  is off, whereby the valves  44  and  46  are closed and the engine  54  is off. In the second position, the valve  44  is opened and the compressor  43  is activated to allow pressurized air flow through line  50  in order to inflate the power lift means  38 . In the third position, the valve  46  is opened to allow pressurized air to flow through lines  48  in order to activate the power cylinders  65 , thereby rotating the support members  61  from a lowered position to a raised position. In the fourth position, the valve  46  is closed, the compressor  43  is inactive, and the valve  44  is opened so that air pressure within the power lift means  38  is released, thereby causing the power lift means to deflate. In the fifth position, the valve  44  is closed, the compressor  43  is inactive, and the valve  46  is opened so that air pressure within the power cylinders  65  is released, thereby causing the support members  61  to rotate from the raised to the lowered position. One skilled in the art can appreciate that other operating or control systems sufficient to power the jack assembly  34  can be used.  
         [0049]    Operation of the Invention  
         [0050]    The jack assembly  34  may first be located between the truck assemblies  26 , typically closer to the truck assembly to be removed. The frame members  56  are sufficiently long to extend between and beyond the track rails  22 , so as to lie across and over the rails. The height of the contracted jack assembly  34 , between the bottom of the frame members  56  and the top of the car engaging means  40 , is sufficiently small to fit within the clearance over the track rails  22  and under the car frame  24 . Approximately 1-2 inches of clearance may be needed between the track rails  22 , jack assembly  34  and the car frame  24 , although a larger clearance of course could be possible.  
         [0051]    The stroke of power lift means  38  may be between perhaps 10-25 inches, sufficient to lift the adjacent end of the railroad car frame  24  completely off of the adjacent wheeled truck assembly  26 , while the other end of the frame  24  remains supported on the opposing wheeled truck  26 .  
         [0052]    After the jack assembly  34  has been positioned over the track rails  22  and under the railroad car  20 , the handle  53  is in the off position, thereby closing the valves  44  and  46 . The valve  46  is then shifted to the second position to open the valve  44 , activate the engine  54  to power the compressor  53 , and inflate the power lift means  38 . The power lift means  38  is inflated until the railroad car frame  24  is spaced apart from the wheeled truck assembly  26  a desired distance.  
         [0053]    In the fully inflated position of power lift means  38  as illustrated in FIG. 5, the support members  61  can be rotated to abut the stops  64 . To operate the power cylinders  65 , the handle  53  may be moved to the third position and the valve  44  may be returned to the closed position. Valve  46  is opened to allow air pressure to activate the power cylinders  65 , and the support members  61  are raised against the lift plate stops  64 , as illustrated in FIG. 5.  
         [0054]    To set the raised jack assembly from the position illustrated in FIG. 5, some air pressure must be released from the power lift means  38  to lower the car engaging means  40  against the support members, as illustrated in FIG. 3. To do this, the pressure at line  50  is first dropped, such as opening valve  44  and stopping both the engine  54  and compressor  43 . The valve  44  is shifted to the closed position when the car engaging means  40  has been lowered onto the cambered edge of the support members  61 .  
         [0055]    When blocked as illustrated in FIG. 3, the jack assembly  34  comprises a solid metal-to-metal triangulated support between the track rails  22  and elevated railroad car  20 , independently of reduced air pressure in the power cylinders  65  or the power lift means  38 . The underlying wheeled truck assembly  26  may then be separated from and rolled out from under the car, and be replaced with another truck assembly, or other servicing can now be done under the railroad car  20 .  
         [0056]    To remove the jack assembly from the lifting position illustrated in FIG. 3, the car engaging means  40  must first be raised again to the position of FIG. 5, to allow the support members  61  to be lowered. Valve  44  is opened and the engine  54  and compressor  43  are activated while the valve  46  remains closed. Once the car engaging means  40  is raised, valve  44  is closed, valve  46  is opened and the engine  53  and compressor  43  are turned off, thereby releasing the air pressure in the power cylinders  65  and lowering the support members  61 . When the support members  61  have been lowered completely, valve  46  is again closed.  
         [0057]    To lower the power lift means  38 , the air pressure in line  50  must again be dropped, as noted above. The valve  44  is then shifted to an open position whereby the air pressure in the power lift means  38  is released. The load from the railroad car  20  on the car engaging means  40  forces the power lift means  38  downward.  
         [0058]    When the valve  44  is opened to release the air pressure from the power lift means  38 , the load from the car engaging means  40  (and possibly the railroad car  20 ) will force air out of the power lift means  38 . Once the railroad car  20  has bottomed out onto the wheeled truck assembly  36 , the weight of the car engaging means  40  will continue to force air out of the power lift means  38  until fully deflated.  
         [0059]    When the power lift means  38  is completely deflated, the valve  46  may be shifted to the closed position, the engine  54  remains stopped, and the jack assembly  34  may be removed from under the railroad car  20 .  
         [0060]    The disclosed jack assembly  34  cooperates directly between the track rails  22  and the car frame  24  to provide a solid metal-to-metal braced support of the elevated railroad car without the need of auxiliary shoring. The triangulated support of the railroad car  20  on the jack assembly  34  between the two track rails  22  and the central sill  23  is stable enough to resist high crosswinds. The disclosed jack assembly  34  is relatively lightweight, capable of being moved about manually or with a small crane, truck lift or the like; and thereby is quite portable, for use at different sites. One person can use the jack assembly effectively and safely, and from only a single side of the railroad car.  
         [0061]    Although the invention has been described with respect to specific illustrated embodiments, it should be understood that the invention is not limited to such embodiments. Additional modifications and/or additions may be included by those skilled in the art, without departing from the scope of the invention as defined by the following claims.