Abstract:
The present invention is directed towards a method for racking or unracking pipe to or from a rack and a device to facilitate the process. The method provides a controllable procedure for inserting or withdrawing the pipe that is less dangerous than prior art methods and does not damage the pipe end. The method entails inserting a pipe gripper having an expansion sleeve into an accessible end of a pipe. The expansion sleeve is forced against an inner wall of the pipe, coupling the pipe gripper to the pipe. Depending upon the application, the pipe is then either pushed fully onto the rack or is pulled partially off the rack. For unracking operations, a crane sling is attached to the partially unracked pipe and the pipe is further manipulated off the rack.

Description:
FIELD OF THE INVENTION 
     The present invention relates to racking and unracking a pipe. In particular, it relates to a method and apparatus for racking and unracking pipe wherein the apparatus has an expansion sleeve. 
     BACKGROUND OF THE INVENTION 
     As shown in FIG. 1, pipes  100  are often warehoused in tiered racks  110 . Three tiers are shown in FIG. 1, but pipe racks having five or more tiers are common in practice. Typically, the warehouse will have an overhead crane for moving the pipes. However, wrapping a crane sling around a pipe  100  disposed in a rack  110  is difficult, especially if the pipe  100  is not located on the top tier. Therefore, it is necessary to partially withdraw the pipe  100  from the rack  110  before the crane sling is wrapped around it. Prior methods of accomplishing this task were dangerous and often resulted in damage to an end of the pipe  100 . 
     The present invention eliminates these drawbacks by providing a controllable means for withdrawing the pipe and reducing the possibility of damage to the pipe. The present invention also provides a useful means for inserting a pipe into a rack with minimal risk of damaging the pipe. A number of prior inventions disclose mechanisms for gripping and manipulating tubular structures, but none will perform satisfactorily when used to rack or unrack pipe. 
     Cullen et al. (U.S. Pat. No. 4,687,244) describe a lifting and reorienting mechanism. The device includes a probe for insertion into an axially extending opening of a structure to be moved. When fully inserted, movement of an outer sleeve deploys tooth-like retractable projections that extend radially from the probe. The retractable projections are forced against the inner wall of the structure to be moved. An important feature of the Cullen et al. device is a dual-arm telescoping actuator that facilitates pivoting of the probe and the structure to be moved. Although this device is capable of performing many useful functions, it is not well suited for the racking and unracking of pipes. The pivoting capability of the device is not required for pipe racking and unracking and might pose a safety hazard should it be accidentally activated. In addition, the retractable projections of the device are likely to damage the inner surface of the pipe. 
     Marzoli (U.S. Pat. No. 4,777,792) discloses a tube gripping device that is designed to be used in textile machines to automatically replace with empty tubes those tubes that have been wrapped with yarn. The gripping device comprises a substantially cylindrical central steel element that has its lower end of frusto-conical shape and is free to slide axially in a cylindrical gripping element. The cylindrical gripping element has its bottom shaped to receive the lower end of the cylindrical steel element. An axial upward movement of the cylindrical central element forces a localized region of the cylindrical gripping element radially outward, thereby pressing that region of the cylindrical gripping element against the inner wall of the tube. The radially outward movement of the cylindrical gripping element is localized in the vicinity of the frusto-conical lower end of the cylindrical central element. In addition, the radial motion is a direct response to the radial component of the force exerted on the cylindrical gripping element by the frusto-conical lower end of the cylindrical central element. The localized nature of the gripping force is not desirable for the pipe racking and unracking application being considered herein. 
     Mistrater et al. (U.S. Pat. No. 5,322,300) describe several variants of a device for supporting hollow cylinders while they are coated with an electrophotographic-imaging layer. The devices comprise an elongated arm with a shaft extending therethrough. The shaft includes a presser means at one end. An expandable disk shaped member is coaxially aligned with and slidably mounted on the shaft between the presser means and an end of the elongated arm. In an undeformed state, the expandable disk shaped member fits in a hollow cylinder with a preferred clearance of about 250 micrometers (0.01 in). Expansion of the disk shaped member is achieved by compressing the member between the presser means and the end of the elongated arm. Additional features of the Mistrater et al. device ensure that a constant force is applied to the hollow cylinder in spite of temperature variations. However, the Mistrater et al. device fails to provide a means for self-orienting the device coaxially with the hollow cylinder. 
     SUMMARY OF THE INVENTION 
     The present invention includes a method for racking and unracking pipe and a device to facilitate the process. For the case in which a pipe needs to be removed from a rack (unracking), the method involves providing a pipe gripper having an expansion sleeve and inserting the pipe gripper into an accessible end of a pipe. After insertion, the pipe gripper is activated, thereby forcing the expansion sleeve against an inner wall of the pipe. With the expansion sleeve pressed against the pipe inner wall, the pipe gripper moves so as to slide a portion of the pipe off the pipe rack. With one end of the pipe supported by the pipe gripper and the other end still supported by the pipe rack, a crane sling is attached to the pipe and the pipe is further manipulated off the rack. The use of a forklift coupled to the pipe gripper further facilitates the process. The new method eliminates the dangerous conditions of prior unracking methods and also avoids the need to repair pipe ends. 
     The case in which a pipe is to be inserted onto a rack (racking) is similar to the unracking process. In the racking process, a pipe that is supported in a crane sling is manipulated so as to place a first end of the pipe on the rack. A pipe gripper having an expansion sleeve is inserted into an accessible end of the pipe and the crane-sling support is removed. The pipe gripper is activated, thereby forcing the expansion sleeve against an inner wall of the pipe and the pipe gripper then moves so as to slide the pipe fully onto the pipe rack. To facilitate the processes, a sophisticated pipe gripper is used. The pipe gripper comprises an expansion sleeve having a distal end a proximal end, and a bore therethrough. A proximal pressure plate abuts the proximal end of the expansion sleeve. A nosepiece is located at the distal end of the expansion sleeve. The nosepiece assists in orienting the pipe gripper coaxially with a pipe to be gripped. A mandrel passes through the bore of the expansion sleeve and is attached to the nosepiece. Tension in the mandrel axially squeezes the expansion sleeve between the nosepiece and the proximal pressure plate. The squeezing forces a radial expansion of the expansion sleeve against an inner wall of the pipe. When pressed against the inner wall of the pipe, the expansion sleeve frictionally couples the pipe to the pipe gripper, thereby allowing the pipe to be moved along its axis. 
     Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be obtained by means of instrumentalities in combinations particularly pointed out in the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings illustrate a complete embodiment of the invention according to the best modes so far devised for the practical application of the principles thereof, and in which: 
     FIG. 1 shows pipes in a three-tiered pipe rack. 
     FIG. 2 shows a preferred embodiment of a pipe gripper in its deactivated mode. 
     FIG. 3 illustrates a pipe gripper coupled with a forklift. 
     FIG. 4 displays a preferred embodiment of a pipe gripper after being activated. 
     FIG. 5 shows a forklift in position to insert a pipe gripper into a pipe on a rack. 
     FIG. 6 displays a forklift and pipe gripper supporting an end of a pipe and a crane sling wrapped around the middle portion of the pipe. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, where similar elements are numbered the same, FIG. 2 illustrates a pipe gripper  130  in its deactivated mode. The pipe gripper  130  comprises an expansion sleeve  140  having a bore  141  therethrough. The expansion sleeve  140  is preferably made from an elastomeric substance, which most preferably has a durometer value ranging from about 70 to about 80. All durometer values reported herein use Shore A. The proximal end  146  of the expansion sleeve  140  abuts against a proximal pressure plate  150 . The distal end  144  of the expansion sleeve  140  is preferably shaped to have an external bevel  148 . A mandrel  180 , having a proximal end  182  and a distal end  184  passes through the bore  141  in the expansion sleeve  140 . The distal end  184  of the mandrel  180  extends beyond the distal end  144  of the expansion sleeve  140  and is attached to a nosepiece  170 . In preferred embodiments, the distal end  184  of the mandrel terminates in an endcap  188  embedded in the nosepiece  170 . In some embodiments the endcap  188  is integral with the mandrel  180 , although in other embodiments the endcap  188  is a separate piece that is secured to the mandrel  180 . Because the radius of the endcap  188  is greater than that of the adjacent portion of the mandrel  180 , the nosepiece  170  is securely attached to the mandrel  180  in this preferred embodiment. 
     The preferred nosepiece  170  has an external shape that is generally cylindrical near its base  174  changing to generally conical near its tip  172 . Preferably, the tip  172  is rounded and the base  174  has an internal bevel  176 . The internal bevel  176  of the base  174  is angled to mate with the external bevel  148  of the distal end  144  of the expansion sleeve  140 . As will be discussed in more detail later, the mating beveled portions of the nosepiece  170  and the expansion sleeve  140  control the bulging of the expansion sleeve  140  when it is axially compressed. Preferably the nosepiece  170  is made from an elastomeric substance with a durometer value of approximately 90. 
     In the most preferred embodiments of the pipe gripper  130 , a distal pressure plate  160  is secured to the mandrel  180  in the region where the nosepiece  170  and the expansion sleeve  140  meet. As shown in FIG. 2, the mandrel  180  preferably includes a flare  186  adjacent to the distal pressure plate  160 . As with the endcap  188 , the flare  186  and the distal pressure plate  160  can be either integral with the mandrel  180  or separate pieces that are secured to the mandrel  180 . 
     In operation, the nosepiece  170  and the expansion sleeve  140  of the pipe gripper  130  are inserted into a pipe. Preferred embodiments include a limiter that limits the axial motion of the pipe gripper  130 . The term “limiter” is intended to include devices such as sophisticated electronic sensors coupled in a feedback loop with the source of axial motion. In the most preferred embodiments (shown in FIGS. 2,  4 ,  5 , and  6 ) the limiter  200  is a bumper pad coupled to the proximal pressure plate  150 . Contact of the bumper pad  200  with an end of a pipe prevents further insertion of the pipe gripper  130  into the pipe. In the most preferred embodiments, the bumper pad  200  is a radial extension of the proximal pressure plate  150 , both pieces being fabricated as a single integral piece of material. The proximal pressure plate  150  is an annular portion of the material contacting the expansion sleeve  140  while the bumper pad  200  extends outside of the region of contact with the expansion sleeve  140 . Most preferably the material is made of an elastomer with a durometer value ranging from about 85 to about 95. In other embodiments the bumper pad  200  is not disposed in the same plane as the proximal pressure plate  150 . Such an arrangement would be preferable if deeper insertion of the expansion sleeve  140  into the pipe were desired. Although the coupling between the bumper pad  200  and the expansion sleeve  140  is indirect, their spatial relationship determines how deeply the expansion sleeve  140  can be inserted into the pipe. 
     With reference again to FIG. 2, in the preferred embodiments, the pipe gripper  130  includes an actuator  210 , a transmission  230 , and a retaining device shown here as a quick-change retainer pin  220 . The quick-change retainer pin  220  couples the proximal end  182  of the mandrel  180  to the transmission  230 . The transmission  230  transforms and transmits the motion of the actuator  210  into axial motion of the mandrel  180 . 
     Preferably, the retaining device allows the assembly that includes the mandrel  180 , the expansion sleeve  140 , and the nosepiece  170  (as well as any parts secured thereto) to easily disconnect from the transmission  230  and be replaced with a new assembly that is sized for a different diameter pipe. The use of a quick-change retainer pin  220  as the retaining device facilitates rapid removal and attachment of the assembly. Whether or not the proximal pressure plate  150  and the bumper pad  200  are also exchanged when a newly sized assembly is put in place depends on the arrangement itself. Exchange of the material used for the proximal pressure plate  150  and the bumper pad  200  is dependent in part upon the size of the material and whether the proximal pressure plate  150  is secured to the expansion sleeve  140  or simply abuts against it. 
     In the most preferred embodiments the transmission  230  comprises a vertical link  238  connected to the actuator  210 , a horizontal link  236  coupled to the mandrel  180  through the use of the quick-change retainer pin  220 , and a bell crank  232 . One lever arm of the bell crank  232  is coupled to the vertical link  238  and the other lever arm of the bell crank  232  is coupled to the horizontal link  236 . In this arrangement, vertical motion from the actuator  210  is transformed to horizontal motion and transmitted to the mandrel  180 . 
     The most preferred embodiments include a housing  250 , which is coupled to the proximal pressure plate  150 . Most preferably, the proximal pressure plate  150  and the bumper pad  200  simply abut against a portion of a housing  250 . In addition, the housing  250  most preferably provides an opening  252  for the mandrel  180  to pass therethrough and an opening  251  for the transmission  230 . Support for the axis of the bell crank  232  is not shown, but the design of such a support is straightforward to those skilled in the art. 
     A forklift bracket  260  is also included in the most preferred embodiments. In the embodiment illustrated in FIG. 2, the actuator  210  is supported by a flange  211  of the forklift bracket  260 . FIG. 3 shows the pipe gripper  130  attached to a forklift  270  through the forklift bracket  260 . Most preferably, a standard side-shifting forklift is used. In particular, the pipe gripper  130  is intended to be coupled with the Model H60XM 3-ton forklift built by the Hyster Company. This forklift  270  can deliver hydraulic pressure to attachments, therefore the use of a hydraulic actuator  210  is preferred. 
     The principles involved in the operation of the pipe gripper  130  are easily surmised through a comparison of the pipe gripper  130  in its undeployed and deployed states in FIGS. 2 and 4, respectively. In the undeployed state in FIG. 2, the expansion sleeve  140  has a substantially constant radius along its length (except for the external bevel  148  at its distal end  144 ). To deploy the pipe gripper  130 , the actuator  210  draws the vertical link  238  upward, thereby rotating the bell crank  232  about its axis and pulling the horizontal link  236 . This applies a tension to the mandrel  180 , thereby pulling the nosepiece  170  and the distal pressure plate  160  toward the proximal pressure plate  150 . This action compresses the expansion sleeve  140  axially, which results in a radial bulging of the expansion sleeve  140 , as shown in FIG.  4 . Reversing the process allows the expansion sleeve  140  to return to its original shape. 
     In the embodiment of FIGS. 2 and 4, both the nosepiece  170  and the distal pressure plate  160  exert compressive forces on the distal end  144  of the expansion sleeve  140 . In some other embodiments, only the distal pressure plate  160  exerts a compressive force on the distal end  144  of the expansion sleeve  140 , and in still other embodiments, only the nosepiece  170  exerts a compressive force on the distal end  144  of the expansion sleeve  140 . In embodiments in which the base  174  of the nosepiece  170  is beveled, the angle of the bevel controls the bulging of the expansion sleeve  140 . Large bevel angles tend to direct the bulging to the middle portion of the expansion sleeve  140  while small bevel angles (or no bevel) often lead to somewhat increased bulging at the proximal  146  and distal  144  ends of the expansion sleeve  140 . When used to grip a pipe, the radial bulging of the expansion sleeve  140  forces the expansion sleeve  140  against an inner wall of the pipe. Large frictional forces between the expansion sleeve  140  and the pipe allow the pipe to be pushed or pulled by the pipe gripper  130 . 
     Although the pipe gripper embodiments described above are preferred, the main feature of the pipe gripper is that it has an expansion sleeve that can be forced outward into engagement with an inner wall of a pipe. 
     FIGS. 5 and 6 show a preferred embodiment of a new pipe unracking method that employs the pipe gripper  130  described above. A pipe  100  is stored on a rack  110 . A pipe gripper  130  is shown coupled to a forklift  270 . In FIG. 5, the expansion sleeve  140  and the nosepiece  170  of the pipe gripper  130  are shown. Preferably a variety of differently sized expansion sleeves  140  can be installed on the pipe gripper  130 . The expansion sleeve  140  chosen is sized to fit inside the pipe  100  with little clearance. With the appropriate expansion sleeve  140  installed, the operator uses the forklift  270  to insert the pipe gripper  130  into an accessible end  102  of the pipe  100 . The inclined sides of the nosepiece  170  help to self-orient the pipe gripper  130  coaxially with the pipe  100 . Interaction of the nosepiece  170  and the pipe  100  tend to push the nosepiece  170  and expansion sleeve  140  into alignment with the pipe  100 . This allows the operator to easily make minor adjustments to the position of the pipe gripper  130  during initial insertion. When the position is correct, the operator moves the forklift  270  forward until the bumper pad  200  contacts the accessible end  102  of the pipe  100 . 
     After the pipe gripper  130  is fully inserted in the pipe  100 , the expansion sleeve  140  of the pipe gripper  130  is forced outward against an inner wall of the pipe  100 . For example, compressive forces on the distal and proximal ends of the expansion sleeve  140  cause radial bulging, thereby forcing the expansion sleeve  140  against the inner wall of the pipe  100 . The friction force between the expansion sleeve  140  and inner wall of the pipe  100  allows the pipe to be slid partially off the rack by reversing the direction of the forklift  270 . 
     Referring to FIG. 6, when the center of gravity  104  of the pipe  100  is clear of the pipe rack  110 , a crane sling  124  is attached to the pipe  100 . In this embodiment, the crane sling  124  is supported by an overhead crane  120  via a crane hook  122 . In other embodiments, a truck-mounted crane, or any device suitable for supporting the crane sling  124 , is substituted for the overhead crane  120 . Also not shown in the figure is an alternate embodiment wherein the accessible end  102  of the pipe  100  is raised slightly by the pipe gripper  130 , thereby permitting the crane sling  124  to be manipulated into position with less of the pipe withdrawn from the rack  110 . This mode of operation is useful under certain circumstances. Referring again to FIG. 6, with the weight of the pipe  100  supported primarily in the crane sling  124 , the pipe  100  is manipulated off the rack  110 . The pipe gripper  130  is removed from the pipe  100  after releasing the compressive forces that forced the expansion sleeve  140  to bulge outward. Depending upon the circumstances, the pipe gripper  130  is removed from the pipe  100  either before or after the pipe  100  is fully off the rack  110 . However, the pipe gripper  130  is not removed until after the weight of the pipe  100  is substantially supported in the crane sling  124 . After the pipe  100  is clear of the rack  110 , the overhead crane  120 , or an appropriate substitute transports it. 
     A method for racking pipe onto a pipe rack  110  is similar to the unracking process described above practiced in reverse. With reference to FIGS. 6 and 5, in the racking process, a pipe that is supported in a crane sling  124  is manipulated so as to place a first end of the pipe  100  on the rack  110 . A pipe gripper  130  having an expansion sleeve  140  sized to fit in the pipe  100  is inserted into an accessible end  102  of the pipe  100 . Preferably, insertion continues until the accessible end  102  of the pipe  100  contacts the bumper pad  200 . After insertion, the pipe  100  is supported at the first end by the rack  110  and at the accessible end  102  by the pipe gripper  130 . In this configuration, the support that is provided by the crane sling  124  is unnecessary and generally undesirable, so the crane-sling support is removed. Preferably, the crane-sling support is removed by lowering the height of the crane sling  124 , thereby removing any pressure that the crane sling  124  might apply to the pipe  100 . Alternatively, the crane-sling support is removed by completely removing the crane sling  124  from around the pipe  100 . However, the preferred approach is more desirable because in it, the crane sling  124  can rapidly resupport the pipe  100  if an emergency situation develops. Either before or after removal of the crane-sling support, but after insertion of the pipe gripper  130 , the pipe gripper  130  is activated, thereby forcing the expansion sleeve  140  against an inner wall of the pipe  100 . With the expansion sleeve  140  pressed against the pipe inner wall, the pipe gripper  130  then moves so as to slide the pipe  100  fully onto the pipe rack  110 . The pipe  100  is considered to be fully on the pipe rack  110  when the pipe gripper  130  can be removed from the pipe  100  without the pipe  100  falling from the rack  110 . With the pipe  100  fully on the rack  110 , the pipe gripper  130  is removed from the pipe  100 . As with the unracking process, coupling a forklift  270  to the pipe gripper  130  greatly facilitates movement of the pipe gripper  130 . 
     The above description and drawings are only illustrative of preferred embodiments which achieve the objects, features and advantages of the present invention, and it is not intended that the present invention be limited thereto. Any modification of the present invention that comes within the spirit and scope of the following claims is considered part of the present invention.