Patent Publication Number: US-2020277828-A1

Title: Saloon door support

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 62/811,704, filed on Feb. 28, 2019, and entitled SALOON DOOR SUPPORT, which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The invention relates generally to supports for bracing a column that is under compression to prevent buckling. More particularly, the present invention relates to swinging supports that move between a first orientation for laterally bracing an axially reciprocating column and a second orientation for allowing a portion of the column to move freely past the supports without lateral bracing. 
     BACKGROUND OF THE INVENTION 
     Long slender columns, in the form of hydraulic (or pneumatic) cylinders, are often used in drilling operations, and, in the form of telescopic cranes, in lifting operations. For example, with reference to  FIGS. 1-5 , a mobile drilling apparatus  100  that may be used to drill holes into ground surfaces to produce oil wells, water wells, etc. is shown. 
     The drilling apparatus  100  includes a mobile base  102 , such as a truck, and a drilling rig (or drilling mast or tower) attached to the base that may be raised to a vertical orientation when in use and lowered to a substantially horizontal orientation when in transport. Among other things, the drilling rig includes a drill rod  101  having a drill bit located at its lower end (not shown) that is designed for cutting and grinding in order to form holes in the ground. A rotary head  104  is mounted to the drill rod  101  and raises and lowers the drill rod during the drilling process. The rotary head  104  is raised and lowered during the drilling process by a hydraulic cylinder  103  that is mounted to the rotary head. The hydraulic cylinder  103  includes a thin inner cylinder rod  105  that has a lower end  107  that is mounted to the mobile base  102 . Throughout the drilling process, the inner cylinder rod  105  remains stationary. A larger outer cylinder barrel  109  is placed over the cylinder rod  105  and moves upwards and downwards during the drilling process. The rotary head  104  described above is mounted to the outer cylinder barrel  109 , which carries the rotary head upwards or downwards. The rotary head  104  and cylinder barrel  109  are shown in a lowered position in  FIG. 4  and in a raised position in  FIG. 5 . The rotary head  104  is slidably mounted to a pair of guide rails  111  located on either side of the outer cylinder barrel that guide the vertical motion of the rotary head. During the drilling process, the hydraulic cylinder  103  raises and lowers the rotary head  104 , guided by the guide rails  111 , and the rotary head  104  raises, lowers, and rotates the drill rod  101  to create a hole in the ground surface. 
     When designing drilling rigs, a primary design goal is to achieve the highest force and longest stoke possible while minimizing the size and weight of the drill. This improves the speed and efficiency of well drilling. However, the ground is often very hard and rocky and, therefore, a tremendous amount of pressure may be exerted on to the hydraulic cylinder  103  as it is raised and lowered. Long slender columns, such as the hydraulic cylinder  103 , tend to buckle and can eventually fail if overloaded with axial compressive force. The maximum axial compressive load that may be applied to a long, slender column while the column remains straight and does not buckle (i.e., the “critical load”) can be determined using Euler&#39;s critical load formula. A simplified version of this formula is reproduced below, where P 1 =the critical load, E=the modulus of elasticity of the column material, I=the minimum area moment of inertia of the cross-section of the column, and L=the unsupported length of the column. 
     
       
         
           
             
               P 
               1 
             
             = 
             
               
                 
                   π 
                   2 
                 
                  
                 EI 
               
               
                 L 
                 2 
               
             
           
         
       
     
     One way to increase the critical load and to reduce the likelihood of a column&#39;s buckling is to increase the size of the mechanical dimensions of the column (e.g., outside diameter). Increasing the outside diameter of a column increases the moment of inertia (I) and, therefore, increases the critical load that the column can withstand before it buckles. However, a disadvantage of increasing the outer diameter of the column (such as the cylinder rod  105  in drilling operations) is that it typically adds to the weight of the system, which adds to the cost and reduces speed of operation. 
     The critical load may also be increased by shortening the unsupported length of the column (L). This is implemented in certain drilling applications by providing a support structure, such as a sliding rod or barrel, between the ends of the thin cylinder rod  105 . These supports keep the cylinder rod  105  centralized (i.e., reduces lateral bowing) and, as a result, can drastically increase the axial compressive force required to buckle the cylinder rod. As shown by the modified Euler critical load equations shown below, if a support is located in the middle of the span of the column, the force (P 2 ) required to buckle that mid-point supported column will be four times the force required to buckle an equivalent unsupported column. If the column is supported in two places by a pair of supports located at ⅓ the length of the column and ⅔ the length of the column, the force (P 3 ) required to buckle the third point supported column will be nine times the force required to buckle an equivalent unsupported column. 
     
       
         
           
             
               P 
               2 
             
             = 
             
               
                 
                   4 
                    
                   
                     π 
                     2 
                   
                    
                   EI 
                 
                 
                   L 
                   2 
                 
               
                
               
                   
               
                
               
                 ( 
                 
                   Mid 
                    
                   
                     - 
                   
                    
                   Point 
                    
                   
                       
                   
                    
                   Bracing 
                 
                 ) 
               
             
           
         
       
       
         
           
             
               P 
               3 
             
             = 
             
               
                 
                   9 
                    
                   
                     π 
                     2 
                   
                    
                   EI 
                 
                 
                   L 
                   2 
                 
               
                
               
                   
               
                
               
                 ( 
                 
                   Third 
                    
                   
                       
                   
                    
                   Point 
                    
                   
                       
                   
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                   Bracing 
                 
                 ) 
               
             
           
         
       
     
     The inner cylinder rod  105  has a smaller outer diameter than the outer diameter of outer cylinder barrel  109 , so buckling is much more likely to occur in the inner cylinder rod than the cylinder barrel. For that reason, typically only the cylinder rod  105  is supported by additional bracing. In many cases, only one support is used, and it is ideally placed in the middle of the unsupported length of the cylinder rod  105 . However, the unsupported length of the cylinder rod  105  changes as the cylinder barrel  109  is raised and lowered over the cylinder rod. For that reason, the ideal location for placing the support to achieve the maximum benefit changes throughout the drilling operation. 
     One solution to this problem is to move the support along the length of the cylinder rod  105  until it reaches the desired position and to adjust the position of the support during the drilling process. One disadvantage to using sliding supports is that a sliding or other support movement mechanism is needed to move the sliding support to the appropriate position along the cylinder rod  105 . This sliding motion causes wear to the system and often requires sealing to prevent hard contaminants from lodging between the hydraulic cylinder rod  105  and the cylinder barrel  109 , which would further increase abrasive wear and cost. Another disadvantage of using sliding supports is that their use often requires the overall length of the cylinder rod  105  to be increased, which increases its unsupported length and may reduce its buckling strength. 
     Accordingly, what is needed is a system and method for bracing a slender column, such as a cylinder rod in a drilling rig, in one or more locations along its length to increase its buckling strength (critical load) without increasing the weight of the column and without causing excessive wear to the column. 
     Notes on Construction 
     The use of the terms “a”, “an”, “the” and similar terms in the context of describing the invention are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising”, “having”, “including” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The terms “substantially”, “generally” and other words of degree are relative modifiers intended to indicate permissible variation from the characteristic so modified. The use of such terms in describing a physical or functional characteristic of the invention is not intended to limit such characteristic to the absolute value which the term modifies, but rather to provide an approximation of the value of such physical or functional characteristic. 
     Terms concerning attachments, coupling and the like, such as “connected” and “interconnected”, refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both moveable and rigid attachments or relationships, unless specified herein or clearly indicated by context. The term “operatively connected” is such an attachment, coupling or connection that allows the pertinent structures to operate as intended by virtue of that relationship. 
     The use of any and all examples or exemplary language (e.g., “such as” and “preferably”) herein is intended merely to better illuminate the invention and the preferred embodiment thereof, and not to place a limitation on the scope of the invention. Nothing in the specification should be construed as indicating any element as essential to the practice of the invention unless so stated with specificity. 
     BRIEF SUMMARY OF THE INVENTION 
     The above and other needs are met by a system for selectively laterally bracing an elongate reciprocating shaft having a first shaft portion, a second shaft portion, a long axis that extends through the first and second shaft portions, and a short axis that is orthogonal to the long axis, wherein the first shaft portion is configured to move along the long axis with respect to the second shaft portion. The system includes a first brace having a switch that is moveable between an engaged orientation and a disengaged orientation. A first contact portion of the switch is configured to be contacted by the first shaft portion as the first shaft portion moves along the long axis past the switch in a first direction. As a result of that contact, the switch moves from the engaged orientation to the disengaged orientation. Additionally, a second contact portion is configured to be contacted by the first shaft portion as the first shaft portion moves along the long axis past the switch in a second direction and, as a result of that contact, the switch moves from the disengaged orientation to the engaged orientation. A bracing member is carried by the switch and has a tip that, when the switch is in the engaged orientation, is located immediately adjacent and laterally braces the second shaft portion by limiting movement of the second shaft portion along the short axis. When the switch is in the disengaged orientation, the tip of the bracing member is not located immediately adjacent the shaft. 
     Certain embodiments of the invention include a second brace. The first and second braces are mounted together as a pair on opposing sides of the elongate reciprocating shaft and rotate simultaneously with one another between the engaged and disengaged orientations such that, in the engaged orientation, the bracing member of the first brace limits movement of the second shaft portion along the short axis in a third direction and the bracing member of the second brace limits movement of the second shaft member along the short axis in a fourth direction. In certain preferred embodiments, a semi-circular tip is formed on the bracing member. That semi-circular tip is located immediately adjacent the second shaft portion in the engaged orientation. In those cases, the second shaft portion has a circular cross section and the semi-circular tip of the bracing member partially surrounds the shaft. Preferably, the semi-circular tips of the first and second braces are mounted together as a pair on opposing sides of the elongate shaft and rotate simultaneously with one another between the engaged and disengaged orientations such that, in the engaged orientation, the semi-circular tips of the bracing members substantially encircle the second shaft portion. 
     Certain embodiments of the invention include a rotation arrester for releasably holding the switch at the disengaged orientation. Certain embodiments of the invention include a rotation limiter that limits the degree of rotation of the switch as the first shaft portion moves along the long axis past the switch in the first direction and the second direction. In some embodiments, the rotation limiter limits the degree of rotation of the switch such that, upon reaching the limit of rotation, the switch is oriented in either the engaged orientation or the disengaged orientation. In certain embodiments, the engaged orientation is offset by approximately 90 degrees of rotation from the disengaged orientation. 
     Certain preferred embodiments of the invention include a bi-stable switch that is automatically biased towards either the disengaged orientation or the engaged orientation when located between the disengaged and engaged orientation. In those cases, the direction of bias is determined by the rotational position of the switch. Preferably, the switch remains stationary when oriented in either the disengaged orientation or the engaged orientation. In certain embodiments, the bi-stable switch includes a first spring connected to a first arm or a second arm of the switch for automatically biasing the switch to the engaged orientation. The bi-stable switch also includes a second spring connected to the other of the first arm and the second arm for automatically biasing the switch to the disengaged orientation. Preferably, the switch is biased to the engaged orientation upon being rotated towards the engaged orientation and beyond a point of maximum potential energy stored in both the first and second springs. Also, the switch is preferably biased to the disengaged orientation upon being rotated towards the disengaged orientation and beyond a point of maximum potential energy stored in both the first and second springs. 
     Other embodiments of the invention provide a bracing system that includes an elongate shaft having a first shaft portion in a reciprocating relationship with a second shaft portion along a long axis that extends through the first and second shaft portions and a short axis that is orthogonal to the long axis. In certain cases, the first shaft portion and the second shaft portion are joined end to end and move together as a single unit along the long axis. Preferably, the second shaft portion has a diameter that is smaller than a diameter of the first shaft portion. 
     A first brace includes a switch that is moveable between an engaged orientation and a disengaged orientation. The switch includes a first contact portion configured to be contacted by the first shaft portion as the first shaft portion moves along the long axis past the switch in a first direction and, as a result of that contact, the switch moves from the engaged orientation to the disengaged orientation. The switch further includes a second contact portion configured to be contacted by the first shaft portion as the first shaft portion moves along the long axis past the switch in a second direction and, as a result of that contact, the switch moves from the disengaged orientation to the engaged orientation. Lastly, a bracing member is carried by the switch. The bracing member has a tip that, when the switch is in the engaged orientation, is located immediately adjacent and laterally braces the second shaft portion by limiting movement of the second shaft portion along the short axis. Additionally, when the switch is in the disengaged orientation, the tip is not located immediately adjacent the shaft. 
     Certain embodiments include a second brace located adjacent the shaft and opposite the first brace. In those cases, the second brace rotates between the engaged and disengaged orientations simultaneously with and in an opposite direction of rotation to the first brace. Preferably, in the engaged orientation, the bracing member of the first brace limits movement of the second shaft portion along the short axis in a third direction and the bracing member of the second brace limits movement of the second shaft portion along the short axis in a fourth direction. 
     Certain embodiments of the invention include a spreader for assisting the switch to rotate between the engaged orientation and the disengaged orientation. The spreader includes tapering sides that contact the first contact portions of both the first and second braces as the first shaft portion moves along the long axis past the switch in the first direction. The tapering sides also contact the second contact portions of both the first and second braces as the first shaft portion moves along the long axis past the switch in the second direction. Preferably, the first contact portions of the first and second braces are guided along the tapering sides as the first shaft portion continues to move in the first direction, which automatically rotates the switch from the engaged orientation to the disengaged orientation. Additionally, the second contact portions of the first and second braces are preferably guided along the tapering sides as the first shaft portion continues to move in the second direction, which automatically rotates the switch from the disengaged orientation to the engaged orientation. 
     Certain embodiments of the invention include a position sensor configured to sense the position of the switch. In certain cases, a controller for controlling an amount of pressured applied along the long axis of the elongate shaft is provided. In those cases, a maximum amount of pressure that may be applied along the long axis of the elongate shaft is at least partially determined by the sensed position of the switch. Preferably, the position sensor sends a signal to the controller when an amount of pressure applied along the long axis of the elongate shaft for a selected position of the switch meets or surpasses a predetermined limit. That warning signal may trigger at least one of: an audible alert generating by an audible alarm connected to the system, a visual alert generated by a visual alarm connected to the system, a reduction pressure applied along the long axis of the elongate shaft, a shutdown of the system. 
     In order to facilitate an understanding of the invention, the preferred embodiments of the invention, as well as the best mode known by the inventor for carrying out the invention, are illustrated in the drawings, and a detailed description thereof follows. It is not intended, however, that the invention be limited to the particular embodiments described or to use in connection with the apparatus illustrated herein. Therefore, the scope of the invention contemplated by the inventor includes all equivalents of the subject matter described herein, as well as various modifications and alternative embodiments such as would ordinarily occur to one skilled in the art to which the invention relates. The inventor expects skilled artisans to employ such variations as seem to them appropriate, including the practice of the invention otherwise than as specifically described herein. In addition, any combination of the elements and components of the invention described herein in any possible variation is encompassed by the invention, unless otherwise indicated herein or clearly excluded by context. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The presently preferred embodiments of the invention are illustrated in the accompanying drawings, in which like reference numerals represent like parts throughout, and in which: 
         FIG. 1  illustrates a mobile drilling rig having an unsupported hydraulic cylinder; 
         FIGS. 2 and 3  are front and side elevation views, respectively, depicting a hydraulic cylinder having an inner cylinder rod located within an outer cylinder barrel; 
         FIGS. 4 and 5  illustrate a mobile drilling rig having a hydraulic cylinder in a lowered and raised position, respectively; 
         FIG. 6  is a front perspective view depicting a saloon door support according to an embodiment of the present invention mounted to guide rails and in an engaged orientation supporting a cylinder rod of a hydraulic cylinder; 
         FIG. 7  is a front perspective view depicting the saloon door support of  FIG. 6  in an disengaged orientation to accommodate a larger cylinder barrel of the hydraulic cylinder; 
         FIGS. 8-10  are front perspective views depicting a saloon door support according to an alternative embodiment of the present invention, where the downwards movement of a hydraulic cylinder barrel rotates the saloon door support from an engaged orientation to an disengaged orientation; 
         FIGS. 11-13  are rear perspective views of the saloon door support of  FIGS. 8-10 ; 
         FIG. 14  is a rear perspective view of a computer-monitored saloon door support according to an alternative embodiment of the present invention; 
         FIGS. 15 and 16  are perspective views of a saloon door support having an asymmetrical oblong spreader and a switch that is magnetically held in engaged and disengaged orientations, respectively, according to an embodiment of the present invention; 
         FIG. 17  is a perspective view illustrating a split bushing mounted to each of two supports of the saloon door support of  FIG. 15 ; and 
         FIGS. 18A-18F  are a series of front elevation views depicting an asymmetrical oblong spreader rotating adjacent supports of a saloon door support from an engaged orientation to a disengaged orientation according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     This description of the preferred embodiments of the invention is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of this invention. The drawings are not necessarily to scale, and certain features of the invention may be shown exaggerated in scale or in somewhat schematic form in the interest of clarity and conciseness. 
     Referring now to  FIGS. 6 and 7 , there is provided an elongate axially reciprocating shaft assembly  200  that includes a support system having saloon door-type motion for laterally bracing an elongate shaft. Although the invention is described herein using terms such as “vertical”, “upwardly” and “downwardly”, and similar terms which are consistent with the orientations of the drawings, the reciprocal movement described herein can be other than along a vertical line. The elongate shaft in the embodiment of  FIGS. 6 and 7  is formed by a first shaft portion  202  and second shaft portion  204 . The shaft includes a long axis  206  that extends vertically through the first shaft portion  202  and the second shaft portion  204  and a short axis (not shown) that is orthogonal to the long axis. The first shaft portion  202  is configured to move axially along the long axis. 
     In the illustrated case, the first shaft portion  202  is hollow with an opening at the bottom end that is placed over one end of the second shaft portion  204  such that the first shaft portion moves upwardly and downwardly along the long axis  206  with respect to the second shaft portion, which remains fixed in place. The first shaft portion  202  is provided with a lower mounting flange  220  and an upper mounting flange  222 . These flanges  220 ,  222  may be used to mount a rotary head (such as rotary head  104  depicted in  FIG. 1 ) to the first shaft portion  202 . 
     The assembly  200  includes a pair of braces (or supports  208 ) that are mounted to a support structure  210  located on either side of the shaft. The support structure  210  could be, for example, the guide rails  111  shown in  FIG. 1  and described earlier that are utilized in certain drilling rig systems. Each support  208  includes a hinge-mounted switch  212  that automatically rotates as the first shaft portion  202  reciprocates upwardly and downwardly between an engaged orientation, where it laterally braces the shaft ( FIG. 6 ), and a disengaged orientation, where it does not laterally brace the shaft ( FIG. 7 ). 
     The switch  212  includes first contact portion  214  that, when the switch  212  is in the engaged orientation, is configured to be contacted by a portion of the shaft as the first shaft portion  202  moves along the long axis past the switch in a first direction. In this particular case, the first shaft portion  202  moves upwardly and downwardly with respect to the second shaft portion  204  and the first direction is defined as a downward motion. However, the first direction could be any other direction (e.g., upward, leftward, rightward, etc.), depending on the orientation of the switch  212  and the shaft. The first contact portion  214  is sized and configured to be contacted by lower mounting flange  220  as the first shaft portion  202  moves downwards past the switch  212 . As a result of the contact between the first shaft portion  202  and the first contact portion  214 , the switch  214  rotates from the engaged orientation to the disengaged orientation. 
     Similarly, the switch  212  includes second contact portion  216  that, when the switch  212  is in the disengaged orientation, is configured to be contacted by a portion of the shaft as the first shaft portion  202  moves along the long axis past the switch in a second direction. In this particular case, the second direction is defined as an upward motion. However, the second direction could be any other direction (e.g., downward, leftward, rightward, etc.), depending on the orientation of the switch  212  and the shaft. The second contact portion  216  is sized and configured to be contacted by upper mounting flange  222  as the first shaft portion  202  moves upwards past the switch  212 . As a result of the contact between the first shaft portion  202  and the second contact portion  216 , the switch  214  rotates from the disengaged orientation to the engaged orientation. 
     In addition to the first and second contact portions  214 ,  216 , the switch  212  also includes a bracing member that is carried by and rotates with the switch between the engaged orientation and the disengaged orientation. In some cases, the bracing member is entirely separate from the first and second contact portions  214 ,  216  of the switch  212 . However, in this case, the first contact portion  214  also functions as a bracing member. When the switch  212  is in the engaged orientation, the bracing member extends towards the shaft and its outermost tip  218 . The tip  218  of the bracing member in this preferred embodiment is semi-circular in shape with a radius that is slightly larger than the radius of second shaft portion  204 . The semi-circular tip  218  is configured to partially surround the circular second shaft portion  204  of the shaft when the switch is in the engaged orientation. When the switch  212  is in the engaged orientation, the tip  218  is located immediately adjacent the second shaft portion. As a result of the proximity between the bracing member and the second shaft portion  204 , the bracing member braces the shaft by limiting lateral movement of the shaft along the short axis. When the switch  212  is in the disengaged orientation, the bracing member (i.e., the first contact portion  214  in this case) is rotated away from the shaft and its outermost tip  218  is not located immediately adjacent the shaft and, therefore, does not limit movement of the shaft along the short axis. 
     The switch  212  is designed to automatically rotate to the disengaged orientation when the first shaft portion  202  moves past the switch so that the bracing member (i.e., first contact portion  214 ) does not brace the first shaft portion  202 . This design would be useful, for example, in drilling rigs where the first shaft portion  202  is a hydraulic cylinder barrel (such as hydraulic cylinder barrel  109  depicted in  FIGS. 2 and 3 ) that does not require bracing and the second shaft portion  204  is a cylinder rod (such as hydraulic cylinder rod  105  depicted in  FIGS. 2 and 3 ) that does require bracing when placed under certain levels of compression. Unlike prior bracing methods, this support  208  is not mounted to the shaft itself and, therefore, does not add to the weight or the length of the shaft. Also, this support  208  is not moved along the shaft and, therefore, does not cause wear to the shaft. Instead, in preferred embodiments, at least a portion of the shaft moves upwardly and downwardly while the support  208  remains stationary. As discussed in greater detail below, as a result of that reciprocating motion, the switch  214  rotates to the engaged orientation only when bracing is required and rotates back to the disengaged orientation when bracing is not required. 
     An alternative embodiment of an elongate reciprocating shaft assembly  300  having a support system with saloon door-type motion for laterally bracing an elongate shaft is depicted in  FIGS. 8-13 . Like assembly  200 , assembly  300  includes an elongate shaft having a first shaft portion  302 , second shaft portion  304 , a long axis  306 , and a short axis (not shown) that is orthogonal to the long axis. The first shaft portion  302  moves axially along the long axis past one or more braces  308  that are mounted to a support structure (not shown) located on either side of the shaft. Each brace  308  includes a hinge-mounted switch  310  that automatically rotates as the first shaft portion  302  moves upwardly and downwardly between an engaged orientation, where the brace laterally braces the shaft, and a disengaged orientation, where it does not laterally brace the shaft. 
     The switch  310  includes an L-shaped rotating member having a first contact portion  312  that, when the switch is in the engaged orientation, is configured to be contacted by a portion of the shaft as the first shaft portion  302  moves downwardly. Similarly, the switch  310  includes a second contact portion  324  that, when the switch is in the engaged orientation, is configured to be contacted by a portion of the shaft as the first shaft portion  302  moves upwardly. More particularly, the first and second contact portions  312 ,  324  are sized and configured to be contacted by a spreader device  314  that is mounted proximate the bottom of the first shaft portion  302  and that moves with the first shaft portion. Depending on the direction that the first shaft portion  302  moves, the spreader device  314  assists in rotating the switch  310  either from the engaged orientation to the disengaged orientation or vice versa. 
     Separate spreader devices may be mounted to the shaft, where a first spreader device assists in rotating the switch from the engaged orientation to the disengaged orientation and a second separate spreader device assists in rotating the switch from the disengaged orientation to the engaged orientation. In the embodiment shown, a single diamond-shaped spreader device  314  assists in both. The spreader device  314  includes first tapering sides  316  that contact the first contact portions  312  of brace  308  as the first shaft portion moves along the long axis  306  past the switch in the first direction and second tapering sides  320  that contact the second contact portions  324  of the brace as the first shaft portion moves along the long axis past the switch in the second direction. 
     When the switch is in the engaged orientation ( FIGS. 8 and 11 ), the spreader device  314  assists in rotating the switch to the disengaged orientation. A first tapering side  316  preferably contacts the first contact portion  312  of the switch  310  to initiate the rotation process. From there, the first contact portion  312  is guided along the first tapering side  316  to continue the rotation process. Similarly, when the switch is in the disengaged orientation ( FIGS. 10 and 13 ), the spreader device  314  assists in rotating the switch to the engaged orientation. A second tapering side  320  preferably contacts the second contact portion  324  of the switch  310  to initiate the rotation process. From there, the second contact portion  324  is guided along the second tapering side  320  to continue the rotation process. 
     The spreader device  314  is preferably sized and configured to automatically snap the switch  310  to the disengaged orientation before the first contact portion  312  reaches the end of first tapering side  316  and to automatically snap the switch to the engaged orientation before the second contact portion  324  reaches the end of second tapering side  320 . In certain embodiments, the switch  310  is bi-stable (i.e., stable in two positions); therefore, when it is positioned between the disengaged and engaged orientations, the switch is automatically biased or rotated towards either the disengaged orientation or the engaged orientation. The direction of the bias is determined by the rotational position of the switch  310 . On the other hand, the switch  310  remains stationary when oriented in either the disengaged orientation or the engaged orientation. Advantageously, a bi-stable switch is always either fully disengaged or fully engaged and is preferably never partially engaged or partially disengaged. 
     The bi-stable switch  310  shown best in  FIGS. 11-13  includes a first spring  322  that is connected between first posts  332  for automatically biasing the switch to the engaged orientation once the switch is rotated sufficiently far towards the engaged orientation. Similarly, the bi-stable switch  310  includes a second spring  326  that is connected between second posts  328  for automatically biasing the switch to the disengaged orientation once the switch is rotated sufficiently far towards the disengaged orientation. The term “spring” should be interpreted broadly to include not only springs but also magnets as well as other similar devices that produce a sufficient strong enough attractive or repulsive force to drive the switch to either the engaged orientation or disengaged orientation. The switch  310  is automatically biased to the engaged orientation upon being rotated towards the engaged orientation and beyond a point of maximum potential energy stored in each of the first and second springs  322 ,  326 . Similarly, the switch  310  is automatically biased to the disengaged orientation upon being rotated towards the disengaged orientation and beyond a point of maximum potential energy stored in both the first and second springs  322 ,  326 . 
     For example, in  FIG. 11 , first spring  322  is minimally stretched and has a minimal amount of stored potential energy (e.g., 20 units of potential energy), whereas second spring  328  is maximally stretched and has a maximal amount of stored potential energy (e.g., 70 units of potential energy). As the switch  310  is rotated counterclockwise (as shown in  FIG. 12 ), the amount of potential energy stored by first spring  322  increases and the amount of potential energy stored by second spring  326  decreases. At some equilibrium or tipping point in that rotation, the amount of potential energy simultaneously stored in each of the springs  322 ,  326  will achieve a maximum value. That point might occur, when each spring stores 45 units of potential energy. Further rotation beyond that point will cause the switch  310  to immediately snap to the position shown in  FIG. 13 . Once that happens, the potential energy stored by first spring  322  will increase, but the potential energy stored by second spring  326  will decrease. 
     In preferred embodiments, the switches  310  snap to either the disengaged orientation or the engaged orientation and securely hold the braces  308  at those positions until a user moves them. To accomplish this, the switches  310  may be provided with one or more rotation arresters, such as pins, ball detents, or other similar devices that are suitable for holding one or more selected positions until acted upon by a sufficient force. Additionally or alternatively, the switches  310  may be provided with a rotation limiter that limits the degree of rotation of the switch  310  as the first shaft portion  302  moves along the long axis past the switch in both the first direction and second direction. Preferably, upon reaching the limit of rotation, the switch  310  is oriented in either the engaged orientation or the disengaged orientation. In preferred embodiments, the rotation limiter includes an upper end  330  that is contacted by the second contact portion  324  when the switch  310  is in the engaged orientation ( FIGS. 8 and 11 ) and a lower end  334  that is contacted by the first contact portion  312  when the switch is in the disengaged orientation ( FIGS. 10 and 13 ). Through such contact, further rotation of the switch  310  is prevented. In this particular case, the rotation limiter is sized and configured such that the engaged orientation is offset by approximately 90 degrees of rotation from the disengaged orientation. In other embodiments, a greater or lesser degree of rotation is allowed. A narrow center portion  336  comprises a notch that connects the upper and lower ends  330 ,  334  and also provides room for the center portion of the switch  310  to be located. In preferred embodiments, the switch  310  is rotatably mounted to the rotation limiter within the center portion  336 . 
     As mentioned previously, the presently-disclosed support system is designed such that the rotation between the engaged orientation and the disengaged orientation occurs automatically as the shaft reciprocates and only during certain portions of the reciprocation cycle. In this particular case, the switch  310  is automatically engaged only when the first shaft portion  302  is adjacent the switch and is automatically disengaged when the second shaft portion  304  is adjacent the switch. This configuration is particularly helpful in the case of drilling rigs, where one portion of the column (e.g., the cylinder rod  106 ) requires lateral bracing but another portion of the column (e.g., the cylinder barrel  109 ) does not require lateral bracing. In this embodiment, the switch  310  automatically rotates to the engaged orientation when bracing is needed (i.e., when the larger diameter first shaft portion  302  slides upwards and exposes the narrower diameter second shaft portion  304 ) and automatically rotates to the disengaged orientation when bracing is not needed (i.e., when the larger diameter first shaft portion  302  slides down over the narrower diameter second shaft portion  304 ). 
     As mentioned earlier, if a column is supported mid-span, the critical load increases to be four times the critical load of an unsupported column. However, if that same column is supported at two points located ⅓ the length of the column and ⅔ the length of the column, the critical load is increased to be nine times the critical load of an unsupported column. Therefore, the more support a column has, the higher its critical load. Accordingly, with reference to  FIG. 14 , an improved version of a mobile drilling apparatus  100 ′ (originally shown in  FIG. 1 ) is provided with a controller  400 , such as a computer, for monitoring, at least partially controlling the operation of the drilling apparatus, or both, and a plurality of pairs of braces  308  mounted to the guide rails  111  adjacent both the thin inner cylinder rod  105  and larger outer cylinder barrel  109  of hydraulic cylinder  103 . 
     The braces  308  are automatically engaged to brace the inner cylinder rod  105  and disengaged when the cylinder barrel  109  surrounds the cylinder rod as the cylinder barrel  109  moves axially with respect to the cylinder rod. The braces  308  in each pair are mounted on opposing sides of the cylinder  103  and include switches that rotate simultaneously with one another between the engaged and disengaged orientations. Both switches include a bracing member for bracing the shaft when in the engaged orientation. The first (e.g., left, as shown in  FIG. 14 ) brace  308  of each pair limits movement of the cylinder  103  along the short axis in a first direction (e.g., leftwards) and the second (e.g. right, as shown in  FIG. 14 ) brace of each pair limits movement of the shaft along the short axis in a second direction (e.g., rightwards). In certain embodiments, both bracing members have semi-circular tips such that, when the switch is in the engaged orientation, the semi-circular tips of the bracing members may substantially encircle a round shaft on all sides. As the column is raised and lowered, the braces automatically rotate between engaged and disengaged orientation. 
     In some embodiments, the braces  308  are provided with position sensors that sense the position of the switch (i.e., whether in the engaged or disengaged orientation) and then send a signal back to the computer  400  that indicates the position of the switches. Based on the position of the switches, the computer  400  may vary the amount of axial pressure exerted on the hydraulic cylinder  103 . This would be beneficial, for example, in the event that the braces  308  were in the disengaged orientation and the hydraulic cylinder  103  was not braced. As discussed above, when a thin shaft is not braced, it can withstand lesser axial loads before buckling. Thus, in the above-described situation, the computer  400  would sense the position of the switches of the braces  308  and would limit the axial load applied to the hydraulic cylinder  103  in order to prevent the shaft from buckling. 
     The position signal sent by the sensor to the computer  400  may also be used for other purposes as well. For example, when an amount of pressure applied along the hydraulic cylinder  103  for a selected position of the switch meets or surpasses a predetermined limit, a warning signal might be triggered. More particularly, if the signal indicates that the hydraulic cylinder  103  is not braced, an audible or visual signal may be triggered once a predetermined amount of axial pressure is applied to the shaft. Further, the signal might also automatically trigger a reduction in the pressure applied to the hydraulic cylinder  103  as a further safety precaution. Finally, the signal might trigger an automatic shutdown of the entire system  100 ′ as a last resort. 
     Referring now to  FIGS. 15 and 16 , an alternative embodiment of an elongate reciprocating shaft assembly  400  having a support system with saloon door-type motion for laterally bracing an elongate shaft is depicted. Assembly  400  includes a pair of braces  408 A,  408 B that are structurally and functionally similar to braces  308  discussed above. Braces  408 A,  408 B each include an L-shaped rotating member. The L-shaped rotating member of the left brace  408 A includes a first contact portion  412 A and a second contact portion  424 A. Similarly, the L-shaped member of the right brace  408 B includes a first contact portion  412 B and a second contact portion  424 B. The first and second springs  322 ,  326  of elongate reciprocating shaft assembly  300  (shown in  FIGS. 11-13 ) are replaced with magnets  432  in this alternative embodiment. Magnets  432  are affixed to each of the brackets  408 A,  408 B and are located within a magnet housing  434  for redirecting the magnetic field of the magnet and strengthening the effective magnetic attractive force. The magnets  432  are designed to magnetically engage the L-shaped rotating member in order to hold it in either the engaged position ( FIG. 15 ) or disengaged position ( FIG. 16 ). 
     In  FIG. 17 , the back of the assembly  400  is shown to better illustrate the structure and arrangement of the braces  408 A,  408 B. The first contact portions  412 A,  412 B of each of the braces  408 A,  408 B includes a pair of tips  440  (located in front of and behind shaft portion  404 ) that are overlapped with corresponding pair of tips. To enable the tips  440  to overlap one another, the braces  408 A,  408 B are vertically offset from one another. In this case, brace  408 A is located slightly below brace  408 B such that the tip  440  of first contact portion  412 B overlaps the tip of first contact portion  412 A. This overlapping configuration provides added strength to the assembly  400  against buckling of shaft portion  404 . In some embodiments, a split bushing half  442  is fixedly attached to each of the first contact portions  412 A,  412 B. Each of the bushing halves  442  are semi-circular in shape so that, in combination, they completely encircle the shaft portion  404 . The bushing halves  442  closely approximate or even touch the shaft portion  404  in order to provide greater resistance to lateral deflection. Preferably, to prevent damaging shaft portion  404 , the bushing halves  442  are formed using a material that is softer than the shaft portion. 
     A single asymmetrical oblong-shaped spreader device  414  for assisting in rotating the L-shaped rotating member of braces  408 A,  408 B from the engaged orientation (Step “A”) through intermediate orientations (Positions “B”-“E”) to the disengaged orientation (Step “F”) when it moves in direction  436  and also in rotating the L-shaped rotating member from the disengaged orientation to the engaged orientation when moving in direction  438  is shown in  FIGS. 18A-18F . Additionally, the shape of the spreader device  414  ensures that the overlapping tips  440  of the braces  408 A,  408 B are correctly overlapped in both the engaged and disengaged orientation. 
     The top and bottom of the spreader device  414  each include a pair of rounded tapering sides, including a first side  416 A having a top end that is vertically offset below an adjoining top end of a second side  416 B. The first and second sides  416 A,  416 B are joined together at their top ends by a vertical lip  430 . This structure is repeated on both the top of the spreader  414  as well as the bottom of the spreader. The first side  416 A joins with the second side  416 B on each of the left and right sides of the spreader  414  at a point  444 . 
     From position “A”, the spreader  414  travels downwards in direction  436  towards the braces  408 A,  408 B, which are in the engaged orientation. The tips  440  are overlapped with first contact portion  412 B spaced vertically above first contact portion  412 A. At position “B”, the bottom first side  416 A of the spreader makes initial contact with the first contact portion  412 B of brace  408 B. Similarly, the bottom second side  416 B of the spreader  414  makes initial contact with first contact portion  412 A of brace  408 A. Through this contact, the braces  408 A,  408 B begin to rotate downwards. At position “C”, first contact portions  412 A,  412 B slide along second side  416 B and first side  416 A, respectively, as the braces  408 A,  408 B continue to rotate downwards as a result of the downwards movement of spreader  414 . As shown at positions “D” and “E”, as the spreader  414  continues downwards, the L-shaped members rotate past an equilibrium point and automatically rotate further such that the second contact portions  424 A,  424 B come to rest on top of the top first side  416 A and top second side  416 B, respectively. As shown at Position “F”, as the spreader  414  continues downwards, the top vertical lip  430  and the positioning of the top first side  416 A with respect to the top second side  416 B, correctly causes the tip  440  of the second contact portion  424 A to be located vertically below the tip of the second contact portion  424 B. The steps are reversed to move the L-shaped rotating members of the braces  408 A,  408 B from the disengaged orientation to the engaged orientation as spreader  414  travels in direction  438 . 
     Although this description contains many specifics, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments thereof, as well as the best mode contemplated by the inventor of carrying out the invention. The invention, as described and claimed herein, is susceptible to various modifications and adaptations as would be appreciated by those having ordinary skill in the art to which the invention relates.