SALOON DOOR SUPPORT

Abstract

A system for bracing a reciprocating shaft having a first shaft portion that moves along a long axis with respect to a second shaft portion and a short axis orthogonal to the long axis. The first shaft portion moves past a switch in a first direction to disengage the switch and past the switch in a second direction to engage the switch. A bracing member is carried by the switch and has a tip that, when the switch is engaged, 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 disengaged, the tip of the bracing member is not located immediately adjacent the shaft.

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's critical load formula. A simplified version of this formula is reproduced below, where P₁=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.

$P_1=\frac{{\pi }^2\mathrm{EI}}{L^2}$

One way to increase the critical load and to reduce the likelihood of a column'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 (P₂) 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 (P₃) required to buckle the third point supported column will be nine times the force required to buckle an equivalent unsupported column.

$P_2=\frac{4{\pi }^2\mathrm{EI}}{L^2}\left(\mathrm{Mid}\text{-}\mathrm{Point}\mathrm{Bracing}\right)$ $P_3=\frac{9{\pi }^2\mathrm{EI}}{L^2}\left(\mathrm{Third}\mathrm{Point}\mathrm{Bracing}\right)$

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 408A, 408B that are structurally and functionally similar to braces 308 discussed above. Braces 408A, 408B each include an L-shaped rotating member. The L-shaped rotating member of the left brace 408A includes a first contact portion 412A and a second contact portion 424A. Similarly, the L-shaped member of the right brace 408B includes a first contact portion 412B and a second contact portion 424B. 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 408A, 408B 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 408A, 408B. The first contact portions 412A, 412B of each of the braces 408A, 408B 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 408A, 408B are vertically offset from one another. In this case, brace 408A is located slightly below brace 408B such that the tip 440 of first contact portion 412B overlaps the tip of first contact portion 412A. 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 412A, 412B. 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 408A, 408B 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 408A, 408B 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 416A having a top end that is vertically offset below an adjoining top end of a second side 416B. The first and second sides 416A, 416B 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 416A joins with the second side 416B 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 408A, 408B, which are in the engaged orientation. The tips 440 are overlapped with first contact portion 412B spaced vertically above first contact portion 412A. At position “B”, the bottom first side 416A of the spreader makes initial contact with the first contact portion 412B of brace 408B. Similarly, the bottom second side 416B of the spreader 414 makes initial contact with first contact portion 412A of brace 408A. Through this contact, the braces 408A, 408B begin to rotate downwards. At position “C”, first contact portions 412A, 412B slide along second side 416B and first side 416A, respectively, as the braces 408A, 408B 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 424A, 424B come to rest on top of the top first side 416A and top second side 416B, 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 416A with respect to the top second side 416B, correctly causes the tip 440 of the second contact portion 424A to be located vertically below the tip of the second contact portion 424B. The steps are reversed to move the L-shaped rotating members of the braces 408A, 408B 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.

Claims

1. 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 comprising:

a first brace having: a switch that is moveable between an engaged orientation and a disengaged orientation; 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; 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; a bracing member carried by the switch and having 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 and, when the switch is in the disengaged orientation, is not located immediately adjacent the shaft.

2. The system of claim 1 further comprising a second brace, wherein 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.

3. The system of claim 1 further comprising a semi-circular tip formed on the bracing member that is located immediately adjacent the second shaft portion in the engaged orientation, wherein the second shaft portion has a circular cross section and the semi-circular tip of the bracing member partially surrounds the shaft.

4. The system of claim 3 further comprising a second brace and semi-circular tips formed on the bracing member of each brace, wherein 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.

5. The system of claim 1 further comprising a rotation arrester for releasably holding the switch at the disengaged orientation.

6. The system of claim 1 wherein the engaged orientation is offset by approximately 90 degrees of rotation from the disengaged orientation.

7. The system of claim 1 further comprising 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.

8. The system of claim 7 wherein 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.

9. The system of claim 1 further comprising 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, wherein the direction of bias is determined by the rotational position of the switch, and wherein the switch remains stationary when oriented in either the disengaged orientation or the engaged orientation.

10. The system of claim 9 further comprising:

a first spring connected to a first arm or a second arm of the switch for automatically biasing the switch to the engaged orientation; and

a second spring connected to the other of the first arm and the second arm for automatically biasing the switch to the disengaged orientation,

wherein 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, and

wherein the switch is 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.

11. A bracing system comprising:

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;

a first brace having: a switch that is moveable between an engaged orientation and a disengaged orientation; 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; 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; a bracing member carried by the switch and having 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 and, when the switch is in the disengaged orientation, is not located immediately adjacent the shaft.

12. The system of claim 11 further comprising:

a second brace located adjacent the shaft and opposite the first brace, wherein the second brace rotates between the engaged and disengaged orientations simultaneously with and in an opposite direction of rotation to the first brace,

wherein, 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.

13. The system of claim 11 further comprising a spreader for assisting the switch to rotate between the engaged orientation and the disengaged orientation, the spreader having:

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 and that 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,

wherein 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 and the second contact portions of the first and second braces are 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.

14. The system of claim 11 further comprising a position sensor configured to sense the position of the switch.

15. The system of claim 14 further comprising a controller for controlling an amount of pressured applied along the long axis of the elongate shaft, wherein 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.

16. The system of claim 15 wherein 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 and wherein that warning signal triggers 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.

17. The system of claim 11 wherein 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.

18. The system of claim 11 wherein the first shaft portion is slidably engaged with the second shaft portion and moves with respect to the second shaft portion.

19. The system of claim 11 wherein the second shaft has a diameter that is smaller than a diameter of the first shaft.