Abstract:
A crimping tool is disclosed that includes a housing assembly carrying a crimping assembly having jaws with engagement surfaces designed to move in the radial direction under controlled load and controlled displacement with application of hydraulic pressure to pistons provided to load the jaws. The crimping tool is designed to be separable into two parts, which facilitates assembly and disassembly of the tool around the work piece for crimping at locations remote from the end of a continuous or long section of pipe. This tool is adapted for use in crimping end fittings onto composite pipe and for use in a field environment where the tool is manually transportable.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/837,394, filed on Aug. 11, 2006, the disclosure of which is expressly incorporated by reference. 
     
     FIELD 
       [0002]    The present application relates generally to applications where metal fittings are crimped to fiberglass/plastic composite pipes. In the field of crimping, this invention relates particularly to applications where long lengths or spools of such composite pipe are field joined by a crimped connection. 
       BACKGROUND 
       [0003]    Pipelines are commonly used to connect individual petroleum wells to more central facilities. Historically these pipelines, or so called gathering lines, have been constructed from lengths of steel pipe, field assembled by welding. In certain applications, where pressure and temperature requirements permit, the use of steel pipe is being replaced by composite plastic/fiberglass pipe. This composite pipe is field supplied in spools of considerable length, greatly reducing the number of field joins required and providing other advantages such as flexibility and corrosion resistance. Nonetheless, while the number of joins is reduced, field joining between the ends of pipe lengths is still required as are connections of the pipe to other elements of the pipeline system. Thus effecting connections at the ends of composite pipes having a high degree of structural and leakage integrity are required. One method or type of connection is made by crimping a fitting to the end of a length of pipe. 
       SUMMARY 
       [0004]    Accordingly, there is provided a crimping tool. The crimping tool comprises a split housing assembly made from a suitably strong and rigid material having a central passageway to accommodate a tubular work piece. The split housing has at least two main body components. The main body components include a structurally rigid joining mechanism. The rigid joining mechanism enables the at least two main body components of the split housing to be separately placed around a tubular work piece and joined to form a generally short thick-walled cylindrical frame enclosing or encircling the work piece. The joining mechanism also enabling the split housing to be separated and removed from the work piece. A crimper assembly is carried by the housing assembly. The crimper assembly has three or more jaws arranged to radially extend and retract. The jaws each carrying a discrete portion of a crimping surface generally shaped to conform to the work piece and positioned to radially engage the outside surface of the work piece when the split housing is placed around the work piece and joined. The crimping assembly has means to apply a selected proportion of radial force to each of the jaws, correlatively providing proportionally distributed radial inward crimping load to the crimping surface. The number of jaws can be selected to distribute portions of the crimping surface according to the needs of the application to accommodate non-axi-symmetric features of the work piece, and the distribution of force can be selected to arrange for controlled radially distributed substantially uniform loading of the jaws or other distribution as may be desirable for a given application. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    These and other features will become more apparent from the following description in which references are made to the following drawings. The drawings are for the purpose of illustration only and are not intended to in anyway limit the scope of the invention to the particular embodiment shown. 
           [0006]      FIG. 1  is an isometric partial cutaway view of a crimping tool with internally located pistons, shown in its retracted position as it would appear with no fluid pressure applied. 
           [0007]      FIG. 2  is an isometric partial cutaway view of the crimping tool with internally located pistons, shown in its engaged position as it would appear with fluid pressure applied, causing the dies to engage to a work piece. 
           [0008]      FIG. 3  is a cross-section view of the crimping tool with internally located pistons shown in its retracted position as it would appear with no fluid pressure applied. 
           [0009]      FIG. 4  is an isometric partial cutaway view of a piston-housing, for use with the crimping tool with internally located pistons. 
           [0010]      FIG. 5  is an isometric view of a lock guide bar, for use with the crimping tool with internally located pistons. 
           [0011]      FIG. 6  is an isometric view of a piston, for use with the crimping tool with internally located pistons. 
           [0012]      FIG. 7  is an isometric partial cutaway view of an alternative embodiment of a crimping tool with internally located pistons, shown in its extended position as it would appear with fluid pressure applied, and including a variable radial piston displacement control. 
           [0013]      FIG. 8  is an isometric partial cutaway view of a crimping tool with externally located pistons, shown in its retracted position as it would appear with no fluid pressure applied. 
           [0014]      FIG. 9  is an isometric partial cutaway view of the crimping tool with externally located pistons, shown in its engaged position as it would appear with fluid pressure applied, causing dies to engage a work piece. 
           [0015]      FIG. 10  is a cross-section view of the crimping tool with externally located pistons, shown in its retracted position as it would appear with no fluid pressure applied. 
           [0016]      FIG. 11  is an isometric partial cutaway view of a piston-housing, for use with a crimping tool with externally located pistons. 
           [0017]      FIG. 12  is a cross-section view of a piston, for use with the crimping tool with externally located pistons. 
           [0018]      FIG. 13  is an isometric partial cutaway view of an alternative embodiment of a crimping tool with externally located pistons, shown in its retracted position as it would appear with no fluid pressure applied, and including a variable radial piston displacement control. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     General Principles 
       [0019]    Crimping is a well known method of fastening metal fittings to hose or pipe having a tubular wall made of more flexible materials such as elastomers or plastic. Typically the metal fitting is coaxially arranged at the end of a hose having an internal support tube placed inside and close fitting with the hose bore and an external ductile sleeve placed outside and close fitting with the exterior surface of the hose forming an annular space filled or largely filled by the hose wall material. This coaxial assembly of fitting and hose or pipe is herein generally referred to as the work piece. In axi-symmetric terms, the crimping method can be explained as a process where sufficient radial or crimping force is applied to the outside of the work piece by a crimping tool causing the ductile sleeve to plastically deform and displace inward in contact with the hose, and upon sufficient displacement induces a through thickness radial stress in the hose wall material correlative with its confinement or interference fit inside the annular space formed between the support tube and ductile sleeve. Upon release of the crimping force, the elastic rebound of the annulus thickness defined by the metal support tube and sleeve components is less than that through the thickness of the confined hose wall material resulting in a residual mechanically induced ‘shrink fit’ stress state. The resulting radial contact forces acting between the hose and fitting surfaces act to directly resist leakage of pressured fluid contained by the hose and mobilize frictional resistance to slippage providing resistance to structural loads enabling axial, bending, shear or torsional forces to be reacted across the fitting and hose. 
         [0020]    However, according to the teaching of the present invention, this simple axi-symmetric explanation fails to distinguish the effects of non-axi-symmetric variables present in the work piece or introduced by the configuration of the crimping tool. Where these effects result in variations in radial stress, such variations can adversely affect the sealing, and possibly also the structural capacity of the crimped connection. 
         [0021]    Crimping tools known to the art, typically do not embody a crimping process that applies the crimping force as a circumferentially uniform (axi-symmetric) radial pressure to the outside of the work piece, instead the prior art crimping tools apply the radial force through two or more jaws configured to each carry a segment of a crimping surface that together largely conforms to and encloses the exterior surface of the work piece interval to be crimped. 
         [0022]    Where such crimping tools employ two such jaws, the jaws are typically arranged to each carry one half of the crimp surface and be in opposition to each other, so that the force applied by one jaw is equally and oppositely reacted by the other, i.e., the force applied by each jaw is equal; however this arrangement will be seen to result in radial displacement of the jaw surfaces, and correlatively change in annular thickness, that varies with relative circumferential position on the work piece, where this variation can be described as having two lobes. It will be appreciated that this variation in radial displacement tends to result in through wall interference variations where the correlative variations in residual radial stress increase with stiffness of the hose wall material. 
         [0023]    Where crimping tools employ more than two jaws, the jaws are typically arranged as a set of linked wedges, vis. a collet, where a common increment of axial displacement results in a proportional increment of radial displacement that is the same for each of the jaws. In this configuration, where the radial displacement is controlled, the radial force applied by each jaw is a dependent variable and depends on the local radial resistance presented by the work piece at the circumferential location of each jaw. Thus where the resistance offered by the work piece varies circumferentially, the resulting residual radial stress of a crimped connection may vary. It will be appreciated that this variation is dependent in part on variations in initial thickness and radial stiffness present in the hose or tube of the crimped work piece. As for crimping methods employing two jaws, it will thus be seen that crimped connections formed by this second method using displacement control of three or more jaws, are more susceptible to localized reductions in radial stress for hose material having greater stiffness or greater circumferential variations in wall thickness. These prior art methods have thus found broad application in applications where the hose wall is constructed of a low stiffness material such as an elastomer. 
         [0024]    The hose wall used in gathering lines is a composite structure of plastic and fiberglass layers. The through wall radial stiffness is thus relatively high, compared to more commonly understood reinforced elastomeric hose. Furthermore, the final wall thickness may vary around the circumference as a function of various manufacturing process variables. This combination of relatively high radial stiffness and thickness variation makes the crimped connection susceptible to the circumferential variations in radial stress allowed by these prior are methods. In contrast, the method incorporated into crimping tools made according to the teachings of the present invention applies a proportionally selected radial load to a plurality of jaws and is thus adapted to compensate for such local variations in thickness. In addition, these tools are provided with means to allow assembly around a work piece enabling lateral removal of the crimping tool from the work piece in applications where removal would otherwise be difficult or impossible, as for example, where the work piece joins two long sections of pipe so that removal, if possible at all, would otherwise require the crimping tool to be moved axially to the end of one of the long joined pipe segments. 
         [0025]    There will now be described in detail two (2) particular crimping tool configurations embodying the method of the present invention, each with two (2) alternative embodiments. 
       Internal Piston Radial Tubular Forming Load Controlled Crimping Tool 
       [0026]    Referring to  FIGS. 1  though  6 , a preferred embodiment of the crimping tool is shown that provides optimized weight and portability. This tool will be referred to here as an internal piston crimping tool. It is shown in  FIG. 1  and generally designated by the numeral  100 , where it is shown in an isometric partial cutaway view as it would appear with no applied fluid pressure. Referring now to  FIG. 2 , the internal piston crimping tool  100  is shown in an isometric partial cutaway view as it would appear with fluid pressure applied to the fluid chambers and the resulting contact between dies  150  and a work piece  101 . 
         [0027]    Referring now to  FIG. 3 , the internal piston crimping tool  100  is shown in a cross-section view as it would appear with no fluid pressure applied. The internal piston crimping tool  100  has two (2) identical piston housings  103  each with a generally semi-cylindrical shape arranged in an opposing manner with the bottom faces  104  located next to one another so that together they form generally cylindrical tool. It will be understood that there may be additional piston housings  103  that, when combined, for a generally cylindrical tool as shown.  FIG. 4  shows an isometric partial cutaway view of a piston housing  103 , with bottom face  104 , generally semi-cylindrical outer surface  105 , and inner bore  106 , that has a plurality of piston bores  107 , in this case three (3), oriented in the radial direction. The piston bores  107  have identical bore profiles and are evenly spaced in a radial plane, in this case sixty (60) degrees from one another, at the centre-point of the internal piston crimping tool. Piston bore  107  with an outer end  108  and an inner end  109 , has a cylindrical section  110  at its inner end  109  and generally cylindrical section  111  including a seal  112  at its outer end  108 . The piston bore  107  has inward facing shoulder  113  that separates the inner cylindrical section  110  from the outer cylindrical section  111 . 
         [0028]    Referring again to  FIG. 4 , piston housing  103  has two (2) lock-guide rails  114  located on opposing sides and adjacent to the bottom face  104 . Lock-guide rail  114  has an outer face  115  and inner face  116  separated by a tapered “dove-tail” profile  117 . Referring now to  FIG. 3 , the internal piston crimping tool  100  has two (2) lock-guide bars  130  with identical but mirrored geometry. Referring now to  FIG. 5 , which shows an isometric view of a lock-guide bar  130 , lock-guide bar  130  has a generally elongate shape, having upper end  131 , lower end  132 , inner stepped surface  133  and outer face  137 . The inner stepped surface  133  of lock-guide bar  130  has a tapered “dove-tail” profile  136 . Referring again to  FIG. 3 , the inverse of the tapered “dove-tail” profile  136  is tapered “dove-tail” profile  117  on lock-guide rail  114  of piston housings  103 . Lock-guide bar  130  slidingly engages with lock-guide rail  114  on both piston housings  103  and attaches the piston housings  103  to one another. Referring again to  FIG. 5 , the front end  134  of the lock-guide bar  130  has a reduced section and acts as a guide rail to aid assembly of the two piston housings  103 . The back end  135  of lock-guide bar  130  has the fully profiled “dove-tail” shape  136 . 
         [0029]    Referring again to  FIG. 4 , the piston housing  103  has a plurality of external fluid ports  118 , in this case two (2), on the front face  119 , located equidistance from two (2) adjacent piston bores  107 . Each fluid port  118  runs perpendicular to the front face  119  of the piston housing  103 , a secondary duct connects this port to inward facing shoulder  113  of piston bore  107 . In conjunction with one another, fluid ports  118  combine to provide fluid interconnectivity between all piston bores  107  in each piston housing  103 , the interconnectivity ensures identical fluid pressure in all fluid chambers  122  while allowing independent displacement of piston  140 . It is understood that the piston housing  103  is not limited to this arrangement of fluid ports, alternatively independent fluid ports could be provided for each fluid chamber and hose connections external to the tool could allow for either independent or interconnected fluid chambers as may be desirable for a given application. 
         [0030]    Referring again to  FIG. 3 , the internal piston crimping tool, crimping assembly has a plurality of piston assemblies, in this case six (6) identical assemblies, each of which includes the following components: a piston  140 , a die  150 , a piston nut  170 , a spring can  180  and a spring  190 . In this case the pistons assemblies are arranged in a plane at the centre-line of the internal piston crimping tool and spaced at even radial intervals, in this case sixty (60) degrees. It is understood that the piston assemblies are not limited to being identical and evenly spaced, and that in the preferred embodiment of the invention the size and spacing of the piston assemblies may be varied within a crimping tool to accommodate circumferential variations in the required applied load distribution to a work piece. Piston  140  is located coaxially in piston bore  107  of piston housing  103 . Referring now to  FIG. 6 , which is an isometric view of piston  140 , with upper end  141  and lower end  142 , piston  140  has a cylindrical lower face  143 , an upward facing shoulder  144 , and a seal  145 . Referring again to  FIG. 3 , piston  140  aligns concentrically with piston bore  107  in the piston housing  103 . The cylindrical surface  146  on the upper end of piston  140  sealingly and slidingly engages with the seal  112  on piston housing  103 . Seal  145  on the lower end  142  of piston  140  slidingly and sealingly engages with the cylindrical surface  110  at the inner end  109  of piston bore  107  in piston housing  103 . The upper end  141  of the piston  140  protrudes through the outer surface  105  of the piston housing  103 . The outer end  141  of the piston  140  threadingly engages with lower end  172  of piston nut  170 . 
         [0031]    Referring still to  FIG. 3 , piston nut  170  with upper end  171 , lower end  172 , downward facing shoulder  173 , and seal  174 , has two (2) opposing torque application faces  175  on the upper end  171 . The seal  174  on the outside diameter of piston nut  170  sealingly and slidingly engages the inside diameter  185  of spring can  180 . 
         [0032]    Referring still to  FIG. 3 , the spring can  180  with upper face  181  and an lower face  182 , is generally cylindrical in shape and hollow and has a plate  183  at the lower end with concentrically located hole  184 , which is large enough to accommodate the upper end  141  of piston  140 . The lower face  182  of the spring can  180  is located next to the outside surface  105  of the piston housing  103 . With application of hydraulic pressure to fluid chamber  122 , piston  140  is stroked fully inwards and the outer face  176  of piston nut  170  becomes flush with the outside face  181  of spring can  180 . With no hydraulic pressure applied, piston  140  is stroked fully in the outward direction and the upward facing shoulder  144  of the piston  140  seats against the inward facing shoulder  113  of piston housing  103 , in this position the upward facing shoulder  177  of piston nut  170  becomes flush with the upper face  181  of spring can  180 . 
         [0033]    Referring still to  FIG. 3 , spring  190  with upper end  191 , and lower end  192 , is generally tubular in shape. (The springs are shown as a Belleville washer stack in all figures, but are not limited to this design, which provides a continually increasing load with axial compression). Upper end  191  of the spring  190  seats against the downward facing shoulder  173  of the piston nut  170 . Lower end  192 , of the spring shoulders against the upper face of plate  183  on the lower end of the spring can  180 . The spring reacts between the piston  140  and the piston housing  103  to return the piston  140  to its full outward stroke with no applied fluid pressure. 
         [0034]    Referring still to  FIG. 3 , the die  150 , with inside cylindrical face  151  has outside cylindrical face  152  which is rigidly attached to lower cylindrical face  143  of piston  140 . Referring now to  FIG. 2 , activation of the internal piston crimping tool with pressure causes the inside cylindrical face  151  of the die  150 , to make contact with the outside face  102  of the work piece  101 . The inside face  151  of the die  150  is designed to provide a generally uniform contact with the outside surface  102  of the work piece  101  when fluid pressure is applied to fluid chamber  122 . 
       Alternative Embodiment of the Internal Piston Radial Tubular Forming Load Controlled Crimping Tool with Variable Radial Piston Displacement Control 
       [0035]    Referring to  FIG. 7 , an alternative preferred embodiment of the crimping tool is shown that provides optimized weight and portability in combination with variable radial piston displacement control. This tool will be referred to here as an internal piston crimping tool with displacement control. It is shown in  FIG. 7  and generally referred to by the numeral  300 . Referring now to  FIG. 7 , the internal piston crimping tool with displacement control is shown in its extended position as it would appear with fluid pressure applied. This embodiment of the crimping tool has piston housings  103 , lock guide bar  130 , spring can  180 , die  150  and spring  190  in common with internal piston crimping tool generally referred to by the numeral  100  and illustrated in  FIGS. 1 through 6 . 
         [0036]    Referring still to  FIG. 7 , this embodiment of the crimping tool has a plurality of pistons  340 , in this case six (6), which are generally cylindrical in shape with a stepped profile. Piston  340 , with upper end  341  lower end  342 , has lower cylindrical face  343 , upward facing shoulder  344  and seal  345 . The upper end  341  of piston  340  has a smooth face  346 , thread element  347 , smooth face  349 , and slot  348  which is oriented along the axis of the piston  340  and intersects face  346 . Piston  340  is assembled in piston bore  107  of piston housing  103  forming fluid chamber  322  between the outward facing shoulder  344  of piston  340  and the inward facing shoulder  113  of piston housing  103 . Seal  345  sealingly and slidingly engages face  110  of piston housing  103 , and seal  112  of piston housing  103  sealingly and slidingly engages face  346  of piston  340 . Lower cylindrical face  343  of piston  340  rigidly attaches to the outside face  152  of die  150 . 
         [0037]    Referring still to  FIG. 7 , this embodiment of the crimping tool has piston nut  370  with upper end  371 , lower end  372 , a radial stop in the form of downward facing shoulder  373 , seal  374 , and opposing torque reaction faces  376  on upper end  371 . Upper end  371  of piston nut  370  has a plurality of threaded holes  379 , in this case four (4), which are equally spaced on a radial plane. Piston nut  370  has internal bore  377 , with thread element  378  and seal  375  at upper end  371 . Downward facing shoulder  382  of piston nut  370  reacts against the upper end  191  of spring  190 . The upper end  341  of piston  340  is assembled coaxially in the internal bore  377  of piston nut  370 , spring  190  and spring can  180 . Thread element  347  of piston  340  threadingly engages with thread element  378  of piston nut  370 . Seal  375  of piston nut  370  sealingly and slidingly engages face  346  of piston  340 , while seal  374  slidingly and sealingly engages the inside face  185  of spring can  180   
         [0038]    Referring still to  FIG. 7 , a threaded screw  380  threadingly engages one of the threaded holes  379  on the upper end  371  of piston nut  370 . The inward facing end  381  of threaded screw  380  engages slot surface  348  of piston  340  to prevent relative movement between piston  340  and piston nut  370 . By removing threaded screw  380  and adjusting the position of piston nut  370  up or down along the axis of piston  340  and then reassembling threaded screw  380 , the axial displacement of the piston  340  is constrained in increments related to the pitch of thread element  378  and the number of threaded holes  379 , such that when pressure is applied to fluid chamber  322  the radial displacement of pistons  340  is restricted as downward facing shoulder  373  of piston nut  370  contacts the upper surface of plate  183  of spring can  180  and reacts the pressure load on piston  340 . 
       External Piston Radial Tubular Forming Load Controlled Crimping Tool 
       [0039]    Referring to  FIGS. 8  though  12 , there will now be described an alternative preferred embodiment of the crimping tool. This embodiment of the crimping tool provides enhanced load capacity, piston stroke, maintainability and functionality. This tool will be referred to here as an “external piston crimping tool”. The external piston crimping tool is shown in  FIG. 8 , and generally designated by the numeral  200 , where it is shown in an isometric partial cutaway view as it would appear with no applied fluid pressure. Now referring to  FIG. 9 , the external piston crimping tool  200  is shown as it would appear with fluid pressure applied and the resulting contact between dies  260  and a work piece  201   
         [0040]    Referring now to  FIG. 10 , the external piston crimping tool  200  is shown in a cross-section view as it would appear with no fluid pressure applied. The external piston crimping tool  200  has two (2) piston housings  203  with a generally semi-cylindrical shape which are arranged in an opposing manner with the lower faces  204  located adjacent to one another so that together they form a generally cylindrical tool. Piston housings  203  are connected using an interlocking engagement, which is separable in a substantially axial direction and resists separation in other directions. In the depicted embodiment, piston housing  203  has a plurality of T-slot or dovetailed keys  214  and  215  on its bottom face  204  which when assembled are arranged so that they mate with the opposite face on the other piston housing  203 . It will be recognized that various interlocking engagements are possible. Referring now to  FIG. 11  which shows an isometric partial cutaway view of piston housing  203 , with bottom surface  204 , generally semi-cylindrical outer surface  205 , and inner bore  206 , has a plurality of piston bores  207 , in this case three (3), oriented in the radial direction with respect to the piston housing  203 . Piston bores  207  all have identical bore profiles and are spaced at even radial intervals, in this case sixty (60) degrees from one another, in a radial plane at the centre-point of the external piston crimping tool  200 . Piston bore  207  with cylindrical outer end  208  and cylindrical inner end  209 , has an outward facing shoulder  212  separating cylindrical sections  208  and  209 . 
         [0041]    Referring again to  FIG. 11 , piston housing  203  has a plurality of female guide splines  214 , in this case (2), and an identical number of male guide splines  215  on lower surface  204 . The guide splines  214  and  215  run parallel to the piston housing axis. The guide splines,  214  and  215 , are located on the lower surface  204  of the piston housing  203 , they mate with the opposite guide splines on the other piston housing. The guide splines  214  and  215  are integral to the piston housing  203  in this embodiment of the design, which eliminates the need for a separate joining component. The male guide splines  215  have upper face  216 , lower face  217  and two (2) profiled tapered faces  218 . The female guide splines  214  have upper face  219 , lower face  220 , and two (2) profiled tapered faces  221  which mate with the corresponding faces on the male spline  214  of the other piston housing  203 . 
         [0042]    Referring again to  FIG. 10 , the external piston crimping tool&#39;s  200  crimping assembly has a plurality of piston assemblies, in this case six (6) identical assemblies, each of which includes the following components: piston  240 , die  260 , can stud  270 , piston cap  280 , and spring  291 . In this case the piston assemblies are arranged in a plane at the centre-line of the tool spaced at even radial intervals, in this case sixty (60) degrees from one another. It is understood that the piston assemblies are not limited to being identical and evenly spaced, and that in the preferred embodiment of the invention the size and spacing of the piston assemblies may be varied within a crimping tool to accommodate circumferential variations in the required applied load distribution to a work piece. Piston assemblies are coaxially located in piston bore  207  of piston housing  203 . Referring now to  FIG. 12 , a cross-section of piston  240  used in the external piston crimping tool  200 , piston  240 , with upper end  241  and lower end  242 , has a cylindrical lower face  243 , and inner bore  244 , has generally cylindrical outer face  245  on its lower end  242  which contains seal  246 . Outer end  241  of piston  240  has a generally cylindrical section  247  which contains seal  248  and wear band  249 . Separating the generally cylindrical upper and lower sections of piston  240  is downward facing shoulder  250 . 
         [0043]    Referring again to  FIG. 10 , the can stud  270  with lower end  271  and upper end  272 , is generally cylindrical in shape with a radial step. A generally cylindrical outside surface  273  at lower end  271  threadingly engages the cylindrical face  212  in piston bore  207  of piston housing  203 . The bottom face  274  of can stud  270  lands on outward facing shoulder  212  of piston bore  207  in piston housing  203 . Can stud  270  also has upward facing shoulders  275  and  276 , generally cylindrical section  277  and upper face  278 . 
         [0044]    Referring still to  FIG. 10 , the piston cap  280  is generally tubular in shape with a plate  281  at the upper end. Generally cylindrical outside surface  282  at the lower end  283  of piston cap  280  threadingly and sealingly engages the generally cylindrical section  277  on the upper end  272  of can stud  270 . The generally cylindrical inside surface  284  at the lower end  283  of piston cap  280  sealingly engages with seal  248  on the upper end  241  of piston  240 . The plate  281  at the upper end  285  of piston cap  280  contains two (2) hydraulic fluid ports  286 . Referring now to  FIG. 9 , hydraulic fluid ports  286  in piston cap  280  allow access to fluid chamber  287 . Fluid in chamber  287  reacts between the downward oriented face  288  of piston cap  280  and the upper face  251  of piston  240  to provide inward radial movement of piston  240  and die  260 . Hydraulic tubing and fittings  289  and  290  respectively provide interconnectivity and pressure equalization between all fluid chambers  222 . It is understood that the external piston crimping tool is not limited to this arrangement of hydraulic tubing and fittings, alternatively independent hydraulic tubing could be run to each of the piston caps  280  which would allow for independent control of fluid pressure in each fluid chamber as may be desirable for a given application. 
         [0045]    Referring now to  FIG. 10 , generally cylindrical spring  291  has upper end  292  and lower end  293 . Upper end  292  of spring  291  reacts against downward facing shoulder  250  of piston  240 , while lower end  293  of spring  291  reacts against upward facing shoulder  275  of can stud  270  to provide radial outward force and movement to the piston  240  and die  260 . (The springs are shown in all figures as a Belleville washer stack that provides a continually increasing load with axial compression, but are they not limited to this design). 
         [0046]    Referring still to  FIG. 10 , die  260  with a general sectioned tubular shape has inner cylindrical face  261  and outer cylindrical face  262 . Outer cylindrical face  262  is rigidly attached to the lower cylindrical face  243  of piston  240 . Referring now to  FIG. 9 , activation of the crimping tool with pressure causes the inside cylindrical face  261  of the die  260 , to make contact with the outside face  202  of the work piece  201 . The inside face  261  of the die  260  is designed to provide a generally uniform contact with the outside surface  202  of the work piece  201  when fluid pressure is applied to fluid chamber  222 . 
       Alternative Embodiment of the External Piston Radial Tubular Forming Load Controlled Crimping Tool with Variable Radial Displacement Control 
       [0047]    Referring to  FIG. 13 , an alternative preferred embodiment of the crimping tool is shown that provides enhanced load capacity and piston stroke in combination with variable radial piston displacement control. This tool will be referred to here as an external piston crimping tool with displacement control. It is shown in  FIG. 13  and generally referred to by the numeral  400 . Referring now to  FIG. 13 , the external piston crimping tool with displacement control is shown in its retracted position as it would appear with no fluid pressure applied. This embodiment of the crimping tool has piston housings  203 , can stud  270 , die  260  and spring  291  in common with external piston crimping tool generally referred to by numeral  200  and illustrated in  FIGS. 8 through 12 . 
         [0048]    Referring still to  FIG. 13 , this embodiment of the crimping tool has a plurality of pistons  440 , in this case six (6), which are generally cylindrical in shape with a stepped profile. Piston  440 , with upper end  441  lower end  442 , has lower cylindrical face  443 , downward facing shoulder  444 , upward facing shoulder  450  and seal  445 . The lower end  442  of piston  440  has seal  449 . The upper end  441  of piston  440  has a smooth face  446 , thread element  447  and slot  448  which is aligned with the axis of the piston and intersects thread element  447 . Piston  440  is assembled coaxially with spring  291  such that the upper end  292  reacts against downward facing shoulder  444 . Lower cylindrical face  443  of piston  440  is rigidly attached to outer face  262  of die  260 . Seal  449  on the lower end  442  of piston  440  slidingly and sealingly engages cylindrical inner surface  209  of piston bore  207  in piston housing  203 . 
         [0049]    Referring still to  FIG. 13 , this embodiment of the crimping tool has piston nut  470  with upper end  471 , lower end  472  and downward facing shoulder  473 , which serves as a radial stop. Upper end  471  of piston nut  470  has a plurality threaded holes  479 , in this case four (4), which are equally spaced in a radial plane. Piston nut  470  has internal bore  474 , with thread element  475 . Thread element  447  of piston  440  threadingly engages with thread element  475  of piston nut  470 . 
         [0050]    Referring still to  FIG. 13 , the piston cap  480  is generally tubular in shape with a stepped profile. Piston cap  480 , with lower end  481  and upper end  482 , has outer surface  483  and upward facing shoulder  484 . Internal bore  485  of piston cap  480  has generally smooth face  486  at lower end  481  and seal  487  at upper end  482  which are separated by downward facing shoulder  488 . Outer surface  483  of piston cap  480  has fluid ports  490  at upper end  482 , thread element  491  and seal  492  at lower end  481 . Piston cap  480  has parallel torque reaction faces  493  at upper end  482 . The upper end  441  of piston  440  is assembled coaxially in the internal bore  485  of piston cap  480 , internal bore of stud can  270  and piston bore  207  of piston housing  203 . Thread element  491  of piston cap  480  threadingly engages with surface  273  of can stud  270 , while seal  492  of piston cap  480  sealingly engages with surface  277  of can stud  270 . Seal  487  of piston cap  480  sealingly and slidingly engages face  446  of piston  440 . Seal  445  of piston  440  slidingly and sealingly engages surface  486  of piston cap  480 . 
         [0051]    Referring still to  FIG. 13 , fluid chamber  422  is formed between the outward facing shoulder  450  of piston  440  and the inward facing shoulder  488  of piston cap  480 . A threaded screw  495  threadingly engages one of the threaded holes  479  on the upper end  471  of piston nut  470 . The inward facing end  496  of threaded screw  495  engages slot surface  448  of piston  440  to prevent relative rotational movement between piston  440  and piston nut  470 . By removing threaded screw  495  and adjusting the position of piston nut  470  up or down along the axis of piston  440  and then reassembling threaded screw  495 , the axial displacement of the piston  440  can constrained in increments related to the pitch of thread element  447  and the number of threaded holes  479 , such that when pressure is applied to fluid chamber  422  the radial displacement of piston  440  is restricted as downward facing shoulder  473  of piston nut  470  comes into contact with upward facing shoulder  484  of piston cap  480  and reacts the pressure load on piston  440 .