Abstract:
An automated low clearance skirt assembly lifting device adapted for raising and lowering a circular or multifaceted skirt to match the opening of pressure vessels such as coking drums and a method for uniform remote operation of the assembly. The low clearance skirt lifting assembly includes a reinforcement of the upper skirt attached to one or more lifting cylinders mounted within a telescoping enclosure, so that the skirt assembly may be uniformly extended and retraced without binding or side load transfer to the hydraulically or pneumatically actuated device. Following the unheading of the flange on the coke drum, the skirt is remotely extended to align with the flange hereby bridging the gap between the chute and the drum prior to commencement of the drilling cycle and lowered once all the coke has been extracted from the drum.

Description:
This application claims benefit of Provisional Application Ser. No. 60/139,040 filed Jun. 10, 1999 and Ser. No. 60/125,202 filed Mar. 18, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     A) Field of the Invention 
     This present invention relates to an apparatus and method for moving coke from a drum, commonly used in the petroleum industry, and directing this coke into a chute. More specifically this invention pertains to an automated low clearance skirt lifting assembly for vertical vessels such as coke drums. It pertains particularly to an automated extendible assembly used in combination with one or more hydraulically or pneumatically actuated members situated within a telescoping assembly. 
     B) Background Art 
     During operation of delayed coking drums for the coking of various heavy hydrocarbon materials in petroleum refining operations, the resulting coke is deposited progressively in the inner walls of the drum and when full, must be periodically removed, usually at 24 hour intervals. A typical apparatus for such coking drums is disclosed by U.S. Pat. No. 4,611,613 to Kaplan. Such coke removal from coking drums is accomplished through an opening in the lower end of a vertically oriented drum, after the bottom head is removed, the skirt is typically raised manually by means of hoisting equipment or automatically by means of single stage hydraulic cylinders. However, because coking drums operate at elevated temperatures, 800-900° F., personnel hazards exist due to exposure of fallout of coke once the head cover is removed. The manual means is hazardous and undesirable. The hydraulically activated means is preferred. However, existing low clearance skirts retrofitted with telescoping cylinders with space limitations have not operated successfully due to volume differential inherent to conventional telescoping cylinders. Single acting cylinders have operated for short periods of time in high clearance applications, but have experienced excessive seal fatigue due to side loading and exposure to the coke dust and corrosive environment. While the prior skirt devices have been found to have serious deficiencies when applied to raising the skirts of coke drums. Such deficiencies have now been advantageously overcome by the present invention. 
     SUMMARY OF THE INVENTION 
     This invention provides an automated skirt lifting device assembly, which is adapted to the remote raising and lowering of skirts on a vertically oriented vessel such as a coking drum. The invention includes a circular or multifaceted connector unit which is attached to the upper portion of the skirt, and one or more extendible enclosures, with internally mounted extendible devices that are hydraulically or pneumatically activated. 
     In one embodiment, for the low clearance application, the extendible device consists of a plurality of short stroke devices mounted with opposing strokes, essentially more than doubling the extension range over the required envelope in the collapsed mode while maintaining staging of the one or more devices due to the commonality of actuating parts and associated surface areas. In the case of the two or more actuating devices, this invention provides a method for equally delivering the actuating force to all units to insure uniform simultaneous extension or retraction of the device. 
     Desirably the skirt device consists of a tubular or multifaceted reinforcement attached to the top edge of the coker skirt with one or more circular, or multifaceted extendible pair of hollow tubes enclosing a low clearance opposedly acting Siamese cylinder. This device is capable of an extended length that is more than double its collapsed length. The inner tube is slidably-mounted within the outer tube and is attached by means of an arm extension to the skirt reinforcement. The outer tube is firmly mounted to the deck or chute structure. The inner tube is slide activated with respect to the outer tube either hydraulically or pneumatically. 
     In one preferred embodiment, the hydraulic system employs the use of two or more conventional hydraulic cylinders joined together at the cylinder body in a Siamese fashion with opposed acting extendible rods attached to identical pistons mounted within the identical bore of each cylinder. Hydraulic oil is provided to all cylinders by means of the lower extension rod which is hollow and encompasses two hydraulic tubes and is bored with two inlet ports and respective oil galleries. This methodology permits the raising of the cylinder barrel without moving the hydraulic line from the metering device. The flow is metered in both the supply and return lines by means of a flow divider which insures simultaneous and equal extension or retraction of each cylinder; thereby eliminating binding of the skirt which is inherent to the use of conventional telescoping cylinders. Also this can be a pneumatic system, using air or steam. 
     To describe the invention in other terms, the skirt section has an upper inlet end which is movable from a lower retracted position to an upper engaged position to receive the coke from the coking drum. There is a plurality of fluid actuators arranged to be in operative engagement with the skirt to move the skirt between its retracted and engaged positions. 
     In one preferred embodiment, each of the actuators comprises first and second cylinder and piston units, having first and second cylinders, respectively, and first and second piston members, respectively, with each piston member comprising a piston and a piston rod. The first and second cylinders are positioned in side by side relationship and arranged so that the first piston member extends in a downward direction from its related cylinder, and the second piston member extends upwardly from its related second cylinder. 
     The lower end of the piston rod of the first piston member is connected to a lower base location, and an upper end of the piston rod of the second piston member is connected to the skirt section. Thus, when each of the fluid actuators are extended, an extension of the first piston member from the first cylinder causes the first and second cylinder members to move upwardly, and an extension of the second piston member from the second cylinder moves the upper end of the piston rod of the second piston member upwardly to move the skirt upwardly towards its upper engaged position. 
     In the hydraulic system of the embodiment described immediately above, there is a first fluid inlet/outlet at the lower end of the first piston rod and a passageway on the first piston rod leading from the first fluid inlet/outlet to a pressure region in an upper part of the first cylinder above the first piston. Thus, fluid from the first inlet/outlet travels upwardly through the passageway of the first piston rod to cause upward movement of the first and second cylinders. 
     Further, there is a first fluid outlet/inlet at the upper pressure region of the first cylinder, leading to a second pressure region in a lower part of the second cylinder and below the first piston in the second cylinder. The fluid flow through the first inlet/outlet causes fluid to flow upwardly through the passageway in the piston rod of the first piston member into the first piston pressure region, and thence into the second pressure region of the second cylinder so as to cause motion said first and second piston members to extend. 
     There is a second fluid outlet/inlet at a lower end of the piston rod of the first piston member through which fluid flows from the piston rod of the first piston member during extension of the first piston member. The piston rod of the first piston member has a fluid outflow passageway having an upper opening at the upper end of the first piston member to receive an outflow of fluid from an annular region between the piston rod of the first piston member and the first cylinder. 
     There is a third fluid inlet/outlet at the lower end of the first cylinder which communicates with the annular region between the first cylinder and the piston rod of the first piston member to receive fluid flow from an annular region that is between the piston rod of the second piston member and the second cylinder. When the first and second pistons are moving toward an extended position, fluid flow from the annular region within the second cylinder flows to the annular region of the first cylinder, thence into the upper opening to the second passageway in the piston rod of the first piston member to flow outwardly through the second outlet/inlet leading from the lower end of the first piston member. 
     In a preferred form, the first passageway of the piston rod of the first piston member comprises a tubular member positioned within the piston rod. The second return passageway in the piston rod of the first piston member comprises an annular passageway defined by a surrounding tubular wall of the piston rod of the first piston member and the tubular member that defines the first passageway in the first piston member. 
     Also in the preferred form, there is for each actuator a telescoping load bearing structure comprising at least first and second load bearing sections located at least partially around the actuator. The first and second load bearing sections have a retracted position when the actuators are in the retracted position and an extended position when the actuators are in the extended position. The first load bearing member engages a base location so as to transfer loads from the first bearing structure to the base location. The second load bearing member operably engages an extending portion of the actuator in a manner to receive torsional and/or lateral loads and transmit these to the first load bearing member to alleviate such lateral and/or torsional loads being imposed solely on the actuators. 
     In the embodiment where there are first and second cylinder and piston units, one section of the load bearing member is positioned at the location of the first and second cylinders, and the other section of the load bearing member is located at the piston of the first cylinder and piston unit. Further, the second load bearing section in the preferred form has an upper end thereof connected to the upper end of the first and second cylinders, and a lower end of the first load bearing member extends downward to a location at which the first end of the lower piston rod is located. 
     In the preferred form, the first and second load bearing sections have non-circular cross sectional configurations to prevent rotational movement relative to one another along a lengthwise axis. In the preferred form, the cross sectional configuration is a rectangular cross sectional configuration. 
     Further, the present invention comprises a locking system where there is at least one locking unit being mounted at a location proximate to an upper portion of the skirt when the skirt is in its upper engaged position. Further, there is a locking element connected to the skirt and being operable to move into a locking location when the skirt is in its upper engaged position. 
     The locking unit comprises a locking arm having a pivot location about which it rotates and an outer end location. The locking arm has a locking member which in a locking position engages a locking element and in a released position is spaced laterally from the locking element. The locking element is arranged so that as the skirt moves upwardly toward its engaged position, and the locking arm is at its lower locking location, the upward movement of the locking element causes movement of the locking arm away from its locking position, and further upward movement of the locking element permits downward movement of the locking arm to its locking position, with the locking member positioned in locking engagement with the locking element. 
     Desirably, the locking element is mounted to the locking arm in a manner that the locking element is moveable toward and away from the pivot mounting location of the locking arm. The locking member is further arranged so that a movement from its locking position toward its released position, the locking member moves to a hold release position to prevent the locking arm from moving to its locking location. 
     In a specific configuration, the locking arm comprises a pair of arm elements having elongate slots therein. The locking member is moveable back and forth within the slots. The locking unit comprises a mounting structure having a locating edge portion which engages the locking member as the locking arm is being moved from the locking to the released position, so as to move the locking member to its hold release position. 
     Also in this preferred configuration, the mounting structure comprises a pair of mounting plates, each having slots which engage the locking member. Thus, the slots in the arm members and the slots in the mounting structure program the movement of the locking member. 
     There is a second embodiment which is similar to the first embodiment, except that each actuator comprises only a single cylinder and piston assembly. The upper end of the piston rod attaches to the skirt and the lower end of the cylinder connects to a base location. Also, in the second embodiment, there is a telescoping load bearing structure comprising the first and second load bearing sections. The first load bearing section has a lower end portion adjacent to a lower end of the cylinder, and the second upper load bearing section has its upper end attached to the upper end of the piston rod. 
     Other features of the present invention will become apparent from the following detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal sectional view taken along the vertical center axis of the apparatus of a first embodiment of the present invention, showing the skirt in its retracted position; 
     FIG. 2 is similar to FIG. 1, but showing the skirt in its extended position for discharging the coke downwardly through the skirt; 
     FIG. 3 is a longitudinal sectional view of one of the cylinder assemblies of their first embodiment in its retracted position, with the section line being taken along the vertical axis of the cylinder assembly; 
     FIG. 4 is a view similar to FIG. 3, but showing the cylinder assembly in its extended position, and also showing the skirt assembly in its retracted position, 
     FIG. 5 is a view of a siamese cylinder and piston component which is part of the assembly shown in FIG. 3, in its retracted position; 
     FIG. 6 is view similar to FIG. 5, but showing the cylinder and piston component in its extended position; 
     FIG. 7 is a schematic view illustrating the hydraulic system for each of the cylinder and piston assemblies. 
     FIG. 8 is a top plan view of the cylinder and piston assembly shown in FIG. 3; 
     FIG. 9 is a side elevational view of one unit of the locking assembly by which the skirt is maintained in its extended position in contact with the coke drum; 
     FIG. 10A is a view similar to FIG. 9, but showing the locking unit in its release position; 
     FIG. 10B is a view looking toward the locking unit of FIG. 1, taken from a position offset by 90 degrees; 
     FIG. 11A is a view similar to FIG. 10A, showing the locking unit in its locking position; 
     FIG. 11B is a view similar to FIG. 10B, viewing the locking unit in its locking position of FIG. 11A; 
     FIG. 12 is view partly in section similar to FIG. 1, showing a second embodiment of the present invention; 
     FIG. 13 is a view of the embodiment of FIG. 12, taken from a location removed 90 degrees from FIG. 12, showing the apparatus in its extended system; 
     FIG. 14 is a side elevational view of the cylinder and piston component of one of the actuators of the second embodiment; 
     FIG. 15 is a side elevational view of one of the actuators of he second embodiment; 
     FIG. 16 is an exploded view showing the components at the upper end of the actuator of FIG. 15, and 
     FIG. 17 is a sectional view taken along line  17 — 17  of FIG.  15 . 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     With reference first to FIG. 1, there is shown a first embodiment of the present invention. There is a coking drum  10  which converges toward a downward location, and at the downward location of the drum  10  there is a discharge portion  11  having a generally cylindrical configuration and defining a cylindrical discharge opening  12 . The discharge portion  11   a  comprises a body flange  13  which has a generally circular configuration, and through which the coke is discharged. 
     There is shown at the bottom of FIG. 1 a  lower chute  14 , which comprises an upper entry cylindrical housing generally designated  15 . 
     There are several I beams  16  as part of the fixed support structure, and there is also a skirt assembly  18  which is supported from the I beams  16 . More particularly, this skirt assembly comprises three telescoping skirt components, namely an inner most skirt  20 , and intermediate skirt  22  and an outer skirt  24 . In other installations, there could be a single skirt which would be of somewhat longer length, or there could be two skirts or possibly more than three skirts. 
     The outer skirt  20  has an outwardly extending lip or flange  26  which rests upon a circumferential supporting flange or member  28 . In operation, this skirt assembly  18 , (or the single skirt if a single skirt is used) is lifted upwardly so that the upper edge of the skirt comes into contact with a downwardly facing surface or member  30  that is part of the discharge body flange  12 . 
     In order to move the skirt assembly  18  from its lower retracted position of FIG. 1 to its upper extended position of FIG. 2, there is provided a plurality of cylinder and piston assemblies  32 . In this present configuration there are generally between two to four of these cylinder and piston assemblies  32 . At this point, it should be noted that a significant part of the present invention is that each of the cylinder and piston assemblies  32  extends to its raised position of FIG. 2 in a manner that the rate of travel of the several cylinder and piston assemblies  32  is the same or within very close tolerances of one another so that the skirt assembly is moved evenly up to its engaged position as shown in FIG.  2 . Also it&#39;s important that the skirt assembly  18  be retracted down to it&#39;s stowed position of FIG. 1 in a manner that the cylinders descend at the same rate so that the upper end of the skirt assembly  18  remains level. 
     In order to support the several cylinders  32  there are provided a number of support members  34  (see FIG. 1) which are connected at one location  36  to the beam  16  and at the opposite end  38  to another beam  40  which is part of stationary structure. 
     Attention is now directed to FIGS. 3 and 4. Each cylinder and piston assembly  32  comprises a tube assembly  41  comprising a fixed tube  42  and an extension tube  44 , and also a cylinder and piston component  45  which is positioned within the tube assembly  41 . 
     The fixed tube  42  has in transverse section a rectangular configuration, and the extension tube  44  has a rectangular cross section generally matching that of the fixed tube  42  so that the extension tube can fit within the fixed tube  42 . In the particular arrangement shown herein, the extension tube  44  has a number of plastic slide plates or pads  46  which are closely adjacent to (but spaced a short distance from) the inner surfaces of the fixed tube  42 . 
     The fixed tube  42  has fixedly attached thereto at its upper end a support flange  48  which in turn engages the related aforementioned support member  34  to provide support. 
     At the lower end of each fixed tube  42  there is a mounting structure  50  that has a trunion mount at  52  to support a horizontally extending pin member  54 . As will described later herein, this pin member attaches to the lower end of the Siamese cylinder and piston component  56  which will be described further below. 
     Attention is now directed to FIGS. 5 and 6 which illustrate the cylinder component  45 . This cylinder component comprises two cylinder and piston units  56  and  58 , respectively. The unit  56  comprises a cylinder  60  and a piston member  61  with a piston  62 , and a piston rod  63 , and in like manner the piston and cylinder unit  58  comprises a cylinder  64  and a piston member  65  with a piston rod  67 . At the upper end of the rod  62 , there is a rod eye with a spherical bearing designated as  68 , and there is at the lower end of the rod  66  a similar spherical bearing  70 . The two cylinders  60  and  64  are interconnected by an upper fitting  71  and a lower fitting  72  to fixedly hold these cylinders  58  and  60  to one another. The upper fitting has two pins  73  which have a trunnion connection to the extendible tube  44 . 
     The lower connecting portion  70  connects directly to the aforementioned pin member  54 . The upper connecting portion  68  of each piston rod  63  is connected to a support arm  74  having one end  75  connecting to the rod end connection  68  and the other end  76  fixedly connected to an upper edge  78  inner skirt component  20 . The upper circumferential portion of the inner skirt  20  has a pair of reinforcing rings  80 . Thus, as each of the piston components  45  are extended, each arm  74  is lifted to in turn lift the inner skirt  20 . The skirt components  20 ,  22  and  24  are so arranged that as each skirt component  20 , 22 , and  24  are raised, the edges  81  inter-engage to move these out to the extended positioned as shown in FIG.  2 . 
     As indicated earlier, it is a significant feature of the present invention that these cylinder and piston assemblies  32  are extended and retracted in a controlled manner to maintain the skirt assembly  18  close to a horizontal position. This will be described with reference to FIG.  7 . 
     For purposes of description, in FIG. 7 the two piston and cylinder components or units  56  and  58  are shown spaced from one another, so that certain hydraulic lines can be shown more clearly. It is to be understood that this is done only for purposes of illustration, and normally these would be positioned immediately adjacent to one another, as shown in FIGS. 5 and 6. 
     The piston rod  67  has an outer cylindrical tubular portion  82  and an inner cylindrical tubular portion  84  mounted concentrically in the outer portion  82 . The inner tube  84  defines a vertically aligned central passageway  86  and the tubes  82  and  84  define a surrounding annular passageway  88 . 
     There is a first inlet port  90  at the lower end of the rod  67  which connects to the passageway  86 . The passageway  86  in turn connects to a passageway  92  in the piston  66  to discharge into the region  96 . Thus, when hydraulic fluid is directed into the port  90 , the fluid flowing into the region  96  causes the two cylinder members  60  and  64  to move upwardly. 
     There is also a port  100  in the upper end of the cylinder  64  which leads from the upper chamber or region  96  and extends downwardly through a tubular portion  102  that leads downwardly and then connects at a port  104  leading to a region  106  beneath the piston  62 . Thus, at the same time that the fluid entering the port  90  and flowing into the chamber or region  96  to raise both cylinders  60  and  64 . The fluid is flowing through the port  104  into the region or chamber  106  to cause the piston  66  to begin moving upwardly within the cylinder  60 . Thus, it can be seen that as the hydraulic fluid is directed through the port  90  the two piston rods  62  and  66  are extending out of their cylinders simultaneously. 
     It should also be noted that while this is described using hydraulic fluid, it would also be possible to make this pneumatic, or also operate under steam pressure. 
     There is also a fluid inlet port  109  which connects to the aforementioned annular passageway  88 . This annular passageway  88  communicates through a port  110  to a chamber or region  112  which is on the opposite side of the piston  94  relative to the chamber or region  96 . 
     Connected to the chamber  112  at a lower location is a port  114  that connects to a transfer tube  116  extending upwardly to lead to a port  118  and into an annular chamber  120  which is, relative to the chamber or region  106  on the opposite side of the piston head  62 . 
     During the operation where there is hydraulic fluid going into the port  90 , so that the two pistons  62  and  66  move the rods  63  and  65  to the extended position, fluid is flowing out of the chambers or regions  120  and  112 . Thus, as fluid flows into the port  90 , fluid is flowing through the port  118  through the tube  116 , out the port  114 , into the chamber  112  into the port  110  and then down the annular passageway  88  to exit out through the port  109 . 
     From the above description, it can readily be recognized that when the cylinder and piston assembly  32  is being retracted, the entire flow pattern is in the opposite direction. As indicated previously, it is also essential that the lowering of the skirt assembly  18  be accomplished in the manner that the skirt assembly remains substantially horizontal. For this reason, the inflow of fluid into the port  109  and the discharge of the fluid through the port  90  during the lowering process is done in a controlled manner. Normally, the fluid would be pumped into the opening  108  at a predetermined volumetric flow and pressure, and the outlet flow through the port  90  would be further controlled and the flow outwardly through the port  90  would be properly metered. 
     The diameter of the pistons  62  and  66  are the same and the diameter of the chambers of the cylinders  60  and  64  are the same. Thus, with the volumetric flow rate to each actuator  32  being the same, in this arrangement the rates of the travel of the several actuators are the same. 
     In order to lock the skirt assembly in its raised position during the transfer of the coke from the chute  10  downwardly through the skirt section  18  and then to the lower chute  14 , there is provided a locking apparatus  124 . This apparatus comprises a plurality of locking units which are spaced around the perimeter of the body flange  13 . For each locking unit  126  there is a related locking finger  128 , with each finger being mounted to the upper end of the inner skirt member  20  at circumferential locations corresponding to those of its related units  126 . 
     Each locking unit  126  comprises a mounting member  130  fixedly connected to the body flange  13 . Each of these mounting members  130  comprises two vertically aligned and parallel plates  132  spaced from one another and extending radially outwardly from the body flange  13 . 
     The locking unit  126  further comprises a locking arm member  134  which in turn comprises two arm sections  136  spaced from one another laterally and positioned on opposite sides of the mounting plates  132 , adjacent to and just outside of the plates  132 . The two arm sections  136  of the locking arm  134  are connected to one another at an upper pivotal mounting connection at  138 , this mounting connection  138  comprising a cylindrical pin that connects the two arm sections  136 . At the opposite end of the locking arm  130  there is an end handle  140  which is a cylindrical member that is fixedly attached to and extends between the outer swing ends of the two arm sections  136 . 
     Each arm section  136  has formed therein a slot  142  which is parallel to a lengthwise axis of its arm sections  136 . Positioned within these two slots  142  is a transversely aligned cylindrical locking member  144  which reaches between the two arm sections  136  to extend through the slots  142 . At the opposite ends of the locking member  144 , there is a collar  145  having a larger diameter than that of the locking member  144  so that it is able to contain the locking member  144  properly positioned within the slots  142  (see FIGS.  10 B and  11 B). Also, each mounting plate  132  is formed with a slot  146 , and the locking member  144  also extends through these two slots  146 . Each slot  146  has an outer relatively short, outwardly and downwardly extending slot portion  148  and also an inner downwardly and inwardly extending slot portion  150 . When the locking member  144  is in its outward position (shown in broken lines in FIG. 9, it is in its release position. When the locking member  144  is in the full line inward position, as shown in FIG. 9, it is in its locking location. 
     Reference is now made to FIGS. 10A,  10 B,  11 A and  11 B, which show other details of the locking apparatus  124 . More specifically, the two mounting plates  124  and the two arm sections  136  are shown in the Figures, as are the outer locating collars  145  which hold the locking member  144  in place. It also can be seen that the locking finger  128  actually comprises two side sections  152 , the upper and outer ends of which are interconnected by a cross member  154 . 
     To describe the operation of the locking apparatus, reference is first made to FIG.  9 . The locking arm  134  is shown in solid lines where it is positioned in its down position. In this position, the locking member  144  in its down and inward position in the inner portions  150  of the two slots  146  in the mounting plates  132 . Also, the locking member  144  is positioned at the furthest radially inward position of the two arm slots  142 . It will be noted that in this position the locking member  144  is above, and vertically aligned with, the locking finger  128 . 
     With further reference to FIG. 9, as the inner skirt member  20  moves upwardly, the locking finger  128  engages the locking member  144  and pushes it upwardly. This causes the locking member  144  to engage the outwardly and upwardly slanting upper surface of the slot portion  150  so that the locking member  144  moves upwardly and outwardly. When the locking member  144  reaches a peak location at  152  of the slot  146 , the locking finger  128  passes upwardly by the locking member  144 . After the locking finger  128  moves upwardly far enough to clear the locking member  144 , the force of gravity causes the locking arm  134  to drop downwardly toward its solid line position of FIG. 9, and the locking member  144  also drops downwardly into the solid line position of FIG.  9 . Then the hydraulic pressure of the fluid that is causing the cylinder and piston assembly  32  to extend can be reduced, and the upper skirt portion  20  will move downwardly just slightly so that outwardly extending portion  156  of the finger  128  rests on the locking member  144 . This is the locking position which is shown in FIGS. 11A and 11B. 
     To move the locking unit  126  to its release position, the cylinder and piston assemblies  32  are pressurized to cause them to raise upwardly a very short distance so as to release the locking member  144 . Then the handle  140  of the locking arm  134  is manually pulled upwardly and outwardly to the release position which is shown in FIG.  10 A. This raises the locking member  144  back up toward the peak location  152 , and the locking member  144  then drops into the outer slot portions  148  to move to the dotted line position in FIG.  9 . 
     It can be seen that in this location after the handle  140  is released, and the locking arm  134  drops downwardly a short distance, the locking member  144  is held in its out position and the locking arm  134  remains in its outer release position as shown in FIG.  10 A. In this position, the skirt assembly  18  can be lowered to its retracted position. At a later time, to return the locking arm to its pre-locking position of FIG. 9, the person grasps the handle  140 , pulls it upwardly and at the same time pushes the locking member  144  inwardly toward the coke drum. This causes the locking member  144  to travel inwardly along the slots  146  in the plates  142 , and then with the handle being released, the locking arm  134  will drop and the locking member  144  will move downwardly in the inner slot portions  150  and return to the position shown in full lines in FIG.  9 . In this position, the locking unit  126  is ready to be again engaged by the locking finger  138  during the next cycle of operation of the apparatus. 
     To review the overall operation of the present invention, let us assume that the coking operation is taking place and the skirt assembly  18  is in its retracted position in FIG.  1 . In the particular installation shown herein, at the completion of the coking process the lower cover that closes the body flange  12  needs to be removed. One method of doing this is to move a carriage underneath the drum  10  on rails, and the large heavy cover is then lowered onto the carriage and the carriage takes it away. Another method would be to swing the cover hydraulically. After the cover has been removed, then the skirt assembly  18  is raised in the manner described above by directing the fluid into the inlet port  90  of the several piston and cylinder assemblies  32 . The upper end of the innermost skirt component  20  at the position of FIG. 2 fits against the lower circumferential edge portion  30  of the body flange  12 . The locking apparatus  124  functions to lock the raised upper skirt  20  in place. When this is accomplished, then the coke in the drum  10  can be discharged by means of multiple high-powered water jets to fall into the chute  14 . 
     After the discharge of the coke is completed, the locking units  126  are moved to their release positions. Then to accomplish a retraction of the skirt component  18 , the fluid is directed through the port  109  to cause the piston and cylinder assemblies  32  to retract in a controlled manner. 
     Another feature of the present invention is the manner in which the lateral and/or torsional loads are reacted in the structure. The two cylinders  60  and  64  are fixedly mounted within the extension tube  44 . Thus, any bending moments imposed upon the cylinders  60  and  64  will be reacted into the extension tube  44  and into the fixed tube  42 . In like manner, any torsional loads caused by forces exerted to rotate the extension tube  44  about its longitudinal axis would be resisted in the same manner. 
     Also, as can be seen from viewing FIG. 4, the extended cylinder assemblies  32  are such that the bending moments and also the torsional moments would be largely resisted by the interaction of these tubes  42  and  44 . 
     Also, a particular advantage of this arrangement of having these siamese piston and cylinder assemblies is that in some installations, the clearance around the perimeter of the inlet end of the chute is rather restricted with regard to its vertical dimension. Thus, as can be seen in FIG. 1, the entire piston and cylinder assemblies  32  are in their retracted positions in a vertical space which is almost one half the space between the body flange  12  and the base structure at  40 . This leaves greater clearance for operating in the area between the body flange  12  and the floor structure  40 . 
     A second embodiment of the present invention is shown in FIGS. 12 through 17. Components of this second embodiment which are similar to those of the first embodiment will be given like numerical designations, with an “a” suffix distinguishing those of the second embodiment. 
     This second embodiment differs from the first embodiment mainly in two ways. First, there are only two skirt sections instead of three. Also, each cylinder and piston assembly  32   a  of this second embodiment comprises only a single cylinder and single piston for each assembly. 
     The coke chute  10   a  is substantially the same (or identical to) the coke chute  10  of the first embodiment and comprises the discharge portion  11   a,  having an end opening  12   a  and also the body flange  13   a.  As indicated above, the skirt assembly  18   a  differs from the skirt assembly  18  in that there are only two skirt components  20   a  and  24   a.  The inner skirt component  20   a  moves in substantially the same manner as in the first embodiment, and the upper edge portion thereof engages the body flange  13   a  during the discharge of the coke. 
     There is a plurality of actuators  32   a , but instead of having the Siamese piston arrangement of the first embodiment, there is only a single cylinder  160   a , a single piston rod  162   a , and also a single piston  164   a.    
     The tube assembly  41  a in the second embodiment is similar to the tube assembly  41  of the first embodiment, except that in the present embodiment the inner extendible tube  44   a  and the outer fixed tube  42   a  have a square cross sectional configuration, since there is only the single cylinder and piston assembly. Also, as can be seen in FIGS. 14,  15  and  17 , there a hydraulic line  166   a  which is positioned within the tube assembly  41   a,  and extends along side of the cylinder  160   a.    
     The upper connection of the piston rod  162   a  through the upper skirt  20   a  is somewhat different than in the first embodiment, and the arrangement of the present embodiment is best shown in FIGS. 15 and 16. There is a main box like support member  170   a , and this is in turn fixedly connected to two angle irons  172   a  on opposite sides thereof. A plurality of bolts  174   a  are inserted through openings in flanges  176   a  of the right angle members  172   a  and thread into a mounting plate  178   a.  The plate  178   a  is fixedly connected to the upper edge of the inner extendible tube  44   a.    
     The piston rod  162   a  has an upstanding attaching member  180   a , the upper end of which is threaded at  182   a . This threaded member  182   a  extends upwardly through a center opening  184   a  in the plate  178   a,  and upwardly through a pair of spacing elements  186   a,  and through a bottom opening  188   a  in the box like member  170   a . The box like member has an upper opening  190   a  so that a nut  192   a  can be threaded onto the upper threaded member  182   a . Also, washers at  194   a  and  196   a  can be provided to be positioned on opposite sides of the flanges  176   a.  A bottom washer  198   a  is positioned between the plate  178   a  and the upper stepped surface portion of the piston rod  162   a , and an upper washer  200   a  is provided. 
     The arrangement of this upper fastening portion of each of the cylinder and piston assemblies  32   a  insures that any loads that are imposed on the cylinder and piston assemblies  32   a  are transferred directly into the upper tubular portion  44   a  and into the lower tubular portions  42   a . Thus, as explained previously herein, this isolates the various lateral and torsion loads that would otherwise be imposed on the cylinder and piston units  160   a.    
     It is believed that the operation of the second embodiment can be readily understood by reading the mode of operation of the first embodiment. Accordingly, this will not be described in detail herein. 
     It is to be recognized that various modifications could be made in the present invention without departing from the basic teachings thereof.