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RELATED APPLICATIONS 
     This application claims the benefit of, and priority to, commonly-invented and commonly-assigned U.S. provisional patent application Ser. No. 62/263,889 filed Dec. 7, 2015. The entire disclosure of 62/263,889 is incorporated herein by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     This disclosure is directed generally to pressure control equipment at the wellhead, and more specifically to a remotely-operated wellhead pressure control apparatus. Broadly, and without limiting the scope of this disclosure, the disclosed pressure control apparatus is a cam-locking wellhead attachment that can secure a connection to a pressurized wellhead connection remotely, without manual interaction at the wellhead. 
     BACKGROUND OF THE DISCLOSED TECHNOLOGY 
     Conventionally, wellhead connections to pressure control equipment are typically made by either a hand union or hammer union. Wellhead operators engaging or disengaging these conventional types of wellhead connections place themselves in danger of injury. The pressure control equipment to be connected to the wellhead is typically heavy, and remains suspended above the wellhead operator via use of a crane. Interacting with the crane operator, a technician at the wellhead below must struggle with the suspended load as it is lowered in order to achieve the proper entry angle into the wellhead to make a secure connection. The wellhead operator must then connect the wellhead to the pressure control equipment to the wellhead, typically via a bolted flanged connection. The bolts must be tightened manually by a person at the wellhead, typically via a “knock wrench” struck with a sledgehammer in order to get the bolts sufficiently tight to withstand the internal operating pressure. During this whole process, as noted, the operator is in physical danger of injuries, such as collision with the suspended pressure control equipment load, or pinched or crushed fingers and hands when securing the connection. 
     Wellhead operators are exposed to similar risks of injury during conventional removal of the pressure control equipment from the wellhead. The removal process is substantially the reverse of the engagement process described in the previous paragraph. 
     There is therefore a need in the well services industry to have a way to safely connect and disconnect pressure control equipment from the wellhead while minimizing the physical danger to human resources in the vicinity. The disclosed remotely-operated wellhead pressure control apparatus, is a hydraulically-actuated and -deactuated system that locks pressure control equipment to the wellhead via a remote control station. 
     SUMMARY AND TECHNICAL ADVANTAGES 
     These and other drawbacks in the prior art are addressed by the disclosed pressure control apparatus. Disclosed embodiments describe a cam lock design with a secondary lock, in which the disclosed pressure control apparatus replaces connections done conventionally either by hammering, torqueing, or with a quick union nut, all of which require the interaction of an operator to perform these operations. In such embodiments, a crane operator may place pressure control equipment (PCE) directly onto the wellhead via the disclosed pressure control apparatus&#39;s highly visible entry guide (“tulip”). The crane operator may then proceed to actuate the pressure control apparatus and secure the pressure control equipment in embodiments where the crane is equipped with the apparatus&#39;s remote controls. In alternative embodiments, a second operator may operate the pressure control apparatus remotely while the crane holds the pressure control equipment in the tulip. In currently preferred embodiments, the disclosed pressure control apparatus allows the pressure control equipment to be secured in the wellhead from up to 100 feet away from the wellhead, although the scope of this disclosure is not limited in this regard. 
     As noted, disclosed embodiments of the disclosed pressure control apparatus provide a secondary mechanical lock feature that holds the locked pressure connection secure without total loss in hydraulic pressure. Preferably, the apparatus may be adapted to fit any conventional well head, and may be available in several sizes, such as (without limitation) for 3-inch to 7-inch pipe. Although not limited to any particular pressure rating, the disclosed pressure control apparatus is preferably rated up to about 15,000 psi MAWP (maximum allowable working pressure). Although the embodiments described in this disclosure are described for applications in the oilfield industry, the disclosed pressure control apparatus is not limited to such applications. It will be appreciated that the apparatus also has applications wherever highly pressurized joint connections can be made more safely by remote actuation and deactuation. 
     Embodiments of the disclosed pressure control apparatus preferably also provide a “nightcap” option to cap the well if there will be multiple operations. Consistent with conventional practice in the field, the apparatus includes a nightcap option, available separately, for sealing off the wellhead while the PCE has been temporarily removed, such as at the end of the day. Embodiments including the nightcap enable the apparatus to remain connected to the wellhead, and wellhead pressure to be retained, in periods when PCE is temporarily removed. In such embodiments, the disclosed pressure control apparatus does not have to be removed and re-installed on the well head every time PCE is removed. Such embodiments obviate the need to suspend wellhead operations unnecessarily just to remove and re-install the apparatus every time PCE is removed. 
     It is therefore a technical advantage of the disclosed pressure control apparatus to reduce substantially the possibility of personal injury to wellhead operators during engagement and disengagement of pressure control equipment from wellheads. In addition to the paramount importance of providing a safe workplace, there are further ancillary advantages provided by the disclosed pressure control apparatus, such as improved personnel morale and economic advantages through reduction of lost time accidents and increased efficiency gains of more rapid rig ups. 
     Another technical advantage of the disclosed pressure control apparatus is that it provides a hands-free, secure, predictable connection between pressure control equipment and the wellhead. The disclosed primary cam-lock, in combination with the secondary lock feature, provides a predictable serviceably-tight connection every time. This is distinction to possible variances in the tightness provided by conventional hand- and knock wrench-tightening of the connection, whose degree of tightness may vary according to the technique and physical strength of the manual operator. 
     A further technical advantage of the disclosed pressure control apparatus is that, in embodiments in which a quick test port is provided, a conventional hand pump can conveniently deliver high pressure fluid to a portion of the pressure connection sealed between two sets of o-rings. It will be appreciated that the o-rings will limit or impede high pressure fluid flow into or out of the portion of the pressure connection between the two sets of o-rings. Embodiments of this disclosure provide a quick test port though the pressure control assembly into the flow-limited portion of the pressure connection. A hand pump may then be used to deliver fluid through the quick test port to the flow-limited portion. This allows the pressure integrity of the seals provided by the o-rings to be tested prior to applying high fluid pressures from the wellhead onto the pressure control apparatus&#39;s pressure connection. In other applications, the quick test port may be used to equalize pressure in the flow-limited portion of the pressure connection during service engagement and disengagement of the pressure control apparatus from the wellhead. 
     According to a first aspect, therefore, this disclosure describes embodiments of a wellhead pressure control fitting comprising a generally tubular Pressure Control Equipment (PCE) adapter having first and second adapter ends, the first adapter end configured to mate with pressure control equipment, the second adapter end providing a shaped end including an adapter end curvature; a generally tubular pressure control assembly having first and second assembly ends, the first assembly end providing a first assembly end interior and a first assembly end exterior, the second assembly end configured to mate with a wellhead; the first assembly end exterior having an exterior periphery, the exterior periphery providing a plurality of cam locks, each cam lock disposed to rotate about a corresponding cam lock pin, each cam lock pin anchored to the first assembly end exterior, each cam lock further providing a cam perimeter curvature; the first assembly end exterior further providing a plurality of cam lock pistons, one cam lock piston for each cam lock, wherein extension and retraction of the cam lock pistons causes rotation of the cam locks in opposing directions about their corresponding cam lock pins; the first assembly end exterior further providing a plurality of locking ring pistons, a locking ring connected to the locking ring pistons at a distal end thereof, the locking ring encircling the first assembly end proximate the cam locks, wherein extension of the locking ring pistons causes the locking ring to move to a position free of contact with the cam locks as the cam locks rotate about the cam lock pins, and wherein retraction of the locking ring pistons causes the locking ring to move so as to restrain the cam locks from rotation about the cam lock pins; the first assembly end interior providing a receptacle for receiving the second adapter end, the second adapter end and the receptacle further each providing cooperating abutment surfaces, the cooperating abutment surfaces forming a high pressure seal between the second adapter end and the receptacle when the second adapter end is compressively received into the receptacle; wherein, as the second adapter end enters the receptacle and engages the cooperating abutment surfaces, extension of the cam lock pistons causes the cam locks to rotate about the cam lock pins, which in turn causes the cam perimeter curvatures on the cam locks to cooperatively bear down on the adapter end curvature, which in turn compresses the second adapter end into the receptacle to form the high pressure seal; and wherein, once the high pressure seal is formed, retraction of the locking ring pistons causes the locking ring to move so as to restrain the cam locks from rotation about the cam lock pins. 
     In a second aspect, embodiments of the wellhead pressure control fitting include that each cam lock further provides a cam perimeter notch, each cam perimeter notch configured to engage the second adapter end as the second adapter end approaches entry into the receptacle. 
     In a third aspect, embodiments of the wellhead pressure control fitting include that the second assembly end further provides a vent line. 
     In a fourth aspect, embodiments of the wellhead pressure control fitting include that the second adapter end provides at least one o-ring seal configured to mate with the receptacle when the second adapter end is received into the receptacle. 
     In a fifth aspect, embodiments of the wellhead pressure control fitting include that the second adapter end provides at least first and second o-ring seals, and in which the first assembly end further provides a quick test port, the quick test port comprising a fluid passageway from the first assembly end exterior through to the first assembly end interior, wherein the quick test port is open to the first assembly end interior at a location selected to lie between the first and second o-ring seals when the second end adapter and the receptacle form the high pressure seal. 
     In a sixth aspect, embodiments of the wellhead pressure control fitting include that the locking ring is in an interference fit with the cam locks when retraction of the locking ring pistons causes the locking ring to move so as to restrain the cam locks from rotation about the cam lock pins. 
     In a seventh aspect, embodiments of the wellhead pressure control fitting include that each cam lock piston is connected to its corresponding cam lock via a pinned cam linkage, each pinned cam linkage including a link arm interposed between the cam lock piston and cam lock, each link arm connected to the cam lock via a first linkage pin, each link arm connected to the cam lock piston by a second linkage pin. 
     In an eighth aspect, embodiments of the wellhead pressure control fitting include that the cooperating abutment surfaces include a machined shoulder surface and a machined slope surface provided on the second adapter end, the receptacle further providing machined surfaces to mate with the shoulder surface and slope surface in forming the high pressure seal. 
     In an ninth aspect, embodiments of the wellhead pressure control fitting include that the PCE adapter is interchangeable with a generally tubular night cap adapter, the night cap adapter having first and second night cap ends, wherein the first night cap end is closed and sealed off against internal pressure, and wherein the second night cap end is dimensionally identical to the second adapter end on the PCE adapter. 
     The foregoing has outlined rather broadly some of the features and technical advantages of the disclosed pressure control apparatus technology, in order that the detailed description that follows may be better understood. Additional features and advantages of the disclosed technology may be described. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same inventive purposes of the disclosed technology, and that these equivalent constructions do not depart from the spirit and scope of the technology as described and as set forth in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of embodiments described in detail below, and the advantages thereof, reference is now made to the following drawings, in which: 
         FIG. 1  is a flow chart illustrating method  100 , describing in summary the engagement and disengagement of currently preferred embodiments of the disclosed pressure control apparatus; and 
         FIGS. 2 through 15  are illustrations depicting details and aspects of a currently preferred embodiment of pressure control assembly  200  operating according to  FIG. 1 , in which  FIGS. 2 through 11  are freeze-frame illustrations in sequence, and in which further: 
         FIGS. 2 and 3  are perspective freeze-frame illustrations depicting adapter  250  approaching entry into pressure control assembly  200 ; 
         FIGS. 4 and 5  are elevation freeze-frames illustrations (unsectioned and partial cutaway views, respectively) depicting an upper portion of pressure control assembly  200 , prior to entry of adapter  250 ; 
         FIGS. 6 and 7  are freeze-frame partial cutaway views depicting the entry of adapter  250  into the upper portion of pressure control assembly  200 ; 
         FIGS. 8 through 10  are magnified freeze-frame partial cutaway views of pressure control assembly  200  as adapter  250  engages its seat in receptacle  260 ; 
         FIG. 11  is a freeze-frame illustration depicting disengagement of adapter  250  from its seat in receptacle  260 ; 
         FIGS. 12 and 13  are perspective freeze-frame illustrations depicting night cap  270  entering and engaging upon pressure control assembly  200 ; and 
         FIGS. 13 to 15  depict quick test ports  500  and associated manifold box  510  provided on pressure control assembly  200 , wherein  FIG. 14  is a section as shown on  FIG. 12 , and  FIG. 15  is a magnified cutaway view of manifold box  510 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference is now made to  FIGS. 1 through 15  in describing the currently preferred embodiments of the disclosed pressure control apparatus. For the purposes of the following disclosure,  FIGS. 1 through 15  should be viewed together. Any part, item, or feature that is identified by part number on one of  FIGS. 1 through 15  will have the same part number when illustrated on another of  FIGS. 1 through 15 . It will be understood that the embodiments as illustrated and described with respect to  FIGS. 1 through 15  are exemplary, and the scope of the inventive material set forth in this disclosure is not limited to such illustrated and described embodiments. 
       FIG. 1  is a flow chart illustrating a method  100 , describing in summary the steps to be followed in engaging the disclosed pressure control apparatus onto a wellhead prior to pressure control operations, and then disengaging the apparatus after the pressure control operations. It should be noted that the embodiment of method  100  illustrated on  FIG. 1  makes use of a night cap option, as will be further described immediately below. In other embodiments of method  100  where the night cap option is not used (such embodiments not illustrated), it will be appreciated that the method steps in which the night cap would otherwise be used will either be simply not performed, or adapted in such a way not to use a night cap. 
     Referring now to  FIG. 1 , In blocks  101  through  107 , the wellhead and the pressure control equipment (“PCE”) to be in pressure communication with the wellhead are prepared for use of the disclosed pressure control apparatus. A pressure control assembly is secured to the top of the wellhead via conventional a flange bolt connection or similar (block  101 ). When the night cap option is provided, the pressure control assembly is secured to the well head in block  101  with the night cap already secured to the assembly via cam locks and a locking ring, as will be described below with reference to  FIGS. 12 and 13 . In order to remove the night cap (block  107 ), a first control valve is activated to release the locking ring (block  103 ), and then a second control valve is activated to release the cam locks (block  105 ). The details of locking ring/cam lock release and engagement will be described below. It will be understood that activation of first and second control valves is advantageously done remotely. As will be also seen in further Figures, the pressure control assembly resents a receptacle for receiving a customized adapter on the PCE side. The adapter is secured to the PCE in block  109 . The PCE is then lowered onto/into the pressure control assembly such that the adapter engages within its receptacle (block  111 ). 
     With further reference to  FIG. 1 , the disclosed pressure control apparatus&#39;s sealing mechanism may then be remotely engaged. First, by remote hydraulic actuation, and as illustrated in block  113 , the second control valve opens and causes cam lock pistons to extend, causing rotation of cam locks. Rotation of the cam locks moves them into an engaged position whereby they forcibly bear down on a shoulder on the adapter (as received into its receptacle). Rotation of the cam locks thus has the effect of pressure sealing the connection between the wellhead and the PCE. Then, again by remote hydraulic actuation, the first control valve opens and causes locking ring pistons to retract, causing a locking ring to move into position over the cam locks and retain them in the engaged position (block  115 ). The locking ring acts primarily a safety device to prevent the cam locks from unintentionally becoming disengaged in the event of, for example, a loss of hydraulic pressure. 
     As further shown on  FIG. 1 , the PCE is now pressure sealed to the wellhead via the disclosed pressure control apparatus and wellhead operations may be conducted (block  117 ). When wellhead operations are complete, the apparatus may be disengaged remotely by essentially reversing the previous steps (block  119 ). First, the locking ring pistons are extended causing the locking ring move away from the cam locks, thereby freeing the cam locks to rotate again. Then the cam lock pistons are retracted, causing the cam locks to rotate in the opposite direction so as to disengage from the shoulder on the adapter (fitted to the PCE). The PCE may then be removed from the wellhead (block  121 ) by withdrawing the adapter (fitted to the PCE) from its receptacle. When the night cap option is provided, the night cap may then be secured again to the pressure control assembly (block  123 ). Securement of the night cap is essentially the reverse of the steps illustrated in blocks  103  and  105 , and a repeat of the steps illustrated on blocks and  113  and  115 , except on the night cap instead of adapter fitted to the PCE. Refer below to  FIGS. 12 and 13  and associated disclosure for further details. 
       FIGS. 2 through 11  are a freeze-frame series of illustrations depicting a first embodiment of method  100  on  FIG. 1  in more detail. In  FIG. 2 , pressure control equipment (“PCE”) is labeled generally as P, and wellhead is labeled generally as W. Pressure control assembly  200  is secured to wellhead W via a conventional bolted flange, although this disclosure is not limited in this regard. The wellhead end of pressure control assembly  200  advantageously provides a customized fitting F to connect to wellhead W. Adapter  250  is secured to PCE P via conventional threading, although again this disclosure is not limited to a threaded connection between PCE P and adapter  250 . 
     In  FIG. 3 , PCE has been lifted and moved over pressure control assembly  200  using, for example, a conventional crane (not shown). Entry of adapter  250  into pressure control assembly  200  is facilitate by tulip  201 , a conically-shaped piece. For reference, locking ring  240  and link arms  235  are also visible on  FIG. 3 . 
       FIG. 4  is an elevation view of a top portion of pressure control assembly  200  in more detail. Tulip  201 , locking ring  240 , link arms  235  and cam locks  220  are visible. It will be appreciated that on  FIG. 4 , locking ring  240  and cam locks  220  are in their disengaged position. One of locking ring pistons  242  is also visible on  FIG. 4  in a partially extended state. Locking ring pistons  242  are preferably conventional hydraulic pistons, and will be illustrated and described in more detail further on. 
       FIG. 5  is the elevation of  FIG. 4 , except in partial cutaway view to illustrate more clearly the component parts of pressure control assembly  200 . Tulip  201 , locking ring  240 , cam locks  220 , link arms  235  and cam lock pistons  222  are all visible on  FIG. 5 . It will also be appreciated that cam lock pistons  222 , link arms  235  and cam locks  220  together form a pinned linkage in which extension and retraction of cam lock pistons  222  will cause cam locks  220  to rotate about cam lock pins  224 . Cam lock pistons  222  are preferably conventional hydraulic pistons. 
       FIG. 6  shows adapter  250  (attached to PCE) entering pressure control assembly  200  with the assistance of tulip  201 . Receptacle  260  for adapter  250  is also illustrated, waiting to receive adapter  250 . Conventional o-rings  252  are visible on adapter  250 . 
       FIG. 7  is the view of  FIG. 6  except that adapter  250  is moving closer to its seat in receptacle  260 .  FIGS. 8 through 10  are magnified freezeframe views as adapter  250  engages its seat in receptacle  260 . As will be described in greater detail further on,  FIGS. 8 and 9  depict noteworthy features regarding the seating of adapter  250  in receptacle  260 . First, adapter  250  is engineered to fit in receptacle  260  so as to provide a high pressure seal when the connection is in compression. Second, shoulder  254  on adapter  250  presents a curvature that is shaped and located to match a corresponding cam curvature  225  (refer  FIG. 9 ) on cam locks  220 . As cam locks  220  rotate responsive to extension of cam lock pistons  222 , cam curvatures  225  on cam locks  220  engage shoulder  254  and compress adapter  250  into receptacle  260 . 
     On  FIGS. 8 and 9 , locking ring  240  has been moved away from cam locks  220  via full extension of locking ring pistons  242  (pistons  242  are not shown on  FIGS. 8 and 9 , see  FIG. 4  instead).  FIGS. 8 and 9  also illustrate the cam lock linkage in more detail, discussed above with reference to earlier Figures. With particular reference to  FIG. 9 , it will be seen that cam locks  220  are disposed to rotate about cam lock pins  224 . Cam locks  220  each present cam curvatures  225 . Cam locks  220  are in pinned linkage connection to cam lock pistons  222  via link arms  235 , and first and second linkage pins  236  and  237 . 
     Referring now to  FIG. 8 , cam locks  220  provide cam lock notches  226  in order to assist capture of shoulder  254  on adapter  250 . With reference now to  FIGS. 9 and 10 , it will be seen that once cam lock notches  226  have engaged shoulder  254 , further rotation of cam locks  220  around cam lock pins  224  encourages snug engagement of cam curvatures  225  on shoulder  254  in order to provide a high pressure seal. The relative dimensions, geometries, locations in space, and paths of travel of cam lock pistons  222 , first and second linkage pins  236  and  237 , link arms  235 , cam locks  220 , cam lock pins  224 , cam lock notches  226  and cam curvatures  225  are all selected, designed and engineered to cooperate with corresponding selections of dimensions and geometries on shoulder  254 , seat surface  255  and slope surface  256  on adapter  250  interfacing with receptacle  260 , all to bring about a high-pressure seal via compression of adapter  250  into receptacle  260 . In preferred embodiments, there is about a 5-thousandths of an inch (0.005″) clearance between the exterior cylindrical surface of adapter  250  and the interior cylindrical surface of receptacle  260 . This clearance allows for a pressure-controlling seal with o-rings  252 . Further, as will be seen on  FIGS. 8 through 10 , adapter  250  provides machined surfaces on seat surface  255  and slope surface  256 . Receptacle  260  also provides corresponding machined surfaces shaped to match seat surface  255  and slope surface  256 . Compression of adapter  250  into receptacle  260  thus enables a machined surface metal-to-metal seal at seat surface  255  and slope surface  256 . This metal-to-metal seal is engineered to contain high pressures—up to about 15,000 psi MAWP in preferred embodiments. However, with reference to the cooperating abutment surfaces at the interface of adapter  250  and receptacle  260 , it will appreciated that the scope of this disclosure is not limited to embodiments providing a machined surface metal-to-metal seal at seat surface  255  and slope surface  256 , and that other embodiments may provide other suitable sealing arrangements. 
     With continuing reference to  FIGS. 8 and 9 , and moving on to  FIG. 10 , the operation of cam locks  220  to compress adapter  250  into receptacle  260  is illustrated, thereby enabling the high pressure seal discussed above. On  FIG. 8 , adapter  250  is entering receptacle  260 . Cam lock pistons  222  are fully retracted, and cam curvatures  225  are disengaged. On  FIG. 9 , extension of cam lock pistons  222  has begun, causing rotation of cam locks  220  about cam lock pins  224  such that cam lock notches  226  have assisted capture of shoulder  254  on adapter  250 . On  FIG. 10 , cam lock pistons  222  are fully extended. The pinned linkage of cam locks  220  to cam lock piston  222  (via link arm  235  and first and second linkage pins  236  and  237 ) will be seen to have translated the extension of cam lock pistons  222  into rotation of cam locks  220  about cam lock pins  224 . Rotation of cam locks  220  about cam lock pins  224  brings cam curvatures  225  to bear on shoulder  254  on adapter  250 . Cooperating abutment surfaces at the contact interface of adapter  250  and receptacle  260  are compressed together to form a high pressure seal. 
     Referring now to  FIG. 10 , it will be seen that the linkage between cam locks  220 , link arms  235  and cam lock pistons  222  is configured so that when cam locks  220  are fully engaged on shoulder  254 , locking ring  240  may be lowered to engage cam locks  220 . Engagement of cam locks  220  by locking ring  240  is via full retraction of locking ring pistons  242  (pistons  242  are not shown on  FIG. 10 , see  FIG. 4  instead). Cam locks  220  also provide cam lock tapers  227  in order to assist capture of cam locks  220  by locking ring  240 . With continuing reference to  FIG. 10 , it will be seen that as locking ring  240  is lowered to retain and secure cam locks  220  in an engaged position on shoulder  254 , corresponding locking ring tapers  241  on locking ring  240  cooperate with cam lock tapers  227  to assist engagement of locking ring  240  on cam locks  220 . In preferred embodiments, locking ring  240  may be shaped and sized to provide an interference fit between itself and cam locks  220  to retain and secure them once fully engaged on cam locks  220 . 
     The action of locking ring  240  to secure cam locks  220  is primarily for safety purposes, to prevent cam locks  220  from becoming disengaged from shoulder  254  on adapter  250  in the event of a loss in hydraulic pressure (or otherwise) potentially compromising the high-pressure seal between adapter  250  and receptacle  260 . However, it will be appreciated from the immediately preceding paragraphs that the interference fit between locking ring  240  and cam locks  220  also enables, as a secondary effect, an additional “squeezing” force on cam locks  220  when fully engaged on shoulder  254  on adapter  250 . 
     It will be appreciated that in preferred embodiments, extension and retraction of cam lock pistons  222  and locking ring pistons  242  may be done by remote hydraulic operation, fulfilling one of the technical advantages of the disclosed pressure control apparatus as discussed earlier in this disclosure. It will be further appreciated that the “engineered motion and fit” of the cooperating parts as illustrated on  FIGS. 8 through 10  are not limited any particular embodiment that might generate a high-pressure seal for a certain size or model of the disclosed pressure control apparatus. It will be appreciated that, consistent with the scope of this disclosure, many such “engineered motion and fit” arrangements may be selected and designed for different sizes or models in which the disclosed pressure control apparatus may be embodied. 
       FIG. 11  illustrates disengagement of the disclosed pressure control apparatus. The mechanism is essentially the reverse of engagement, described above with reference to  FIGS. 6 through 10 . Extension of locking ring pistons  242  (refer  FIG. 4 ) disengages locking ring  240  from cam locks  220 , enabling release of cam locks  220 . Retraction of cam lock pistons  222  causes cam locks  220  to rotate around cam lock pins  224  and release cam curvatures  225  from shoulder  254  on adapter  250 . Adapter  250  may then be withdrawn from receptacle  260 . It will be appreciated from  FIG. 11  that when cam locks  220  are in a disengaged state, locking ring  240  advantageously does not make contact with cam locks  220 . This separation between locking ring  240  and disengaged cam locks  220 /link arms  235  applies whether locking ring pistons  242  (refer  FIG. 4 ) are in an extended or retracted state.) 
     Referring now to commonly invented, commonly-assigned U.S. provisional patent application Ser. No. 62/263,889, incorporated herein by reference, FIGS. 2 through 13 in 62/263,889 are a freeze-frame series of illustrations depicting a second embodiment of method  100  on  FIG. 1  in more detail. The second embodiment of method  100 , as illustrated on FIGS. 2 through 13 of 62/263,889, is very similar to the embodiment depicted on  FIGS. 2-11  in this disclosure, except that, primarily, (1) cam locks  220  in 62/263,889 are shaped more smoothly and do not provide a notch corresponding to cam lock notches  226  in this disclosure, (2) locking ring  240  in 62/263,889 is shaped and configured to be received onto link arms  235  in 62/263,889 rather than directly onto cam locks  220  in this disclosure, and (3) the geometry of the linkage (and path of travel of the linked components) for cam locks  220 , link arms  235  and cam lock pistons  222  in 62/263,889 is different than in this disclosure. 
     While both the embodiment disclosed in FIGS. 2 through 13 in 62/263,889 (and associated text) and the embodiment described with reference to  FIGS. 2 through 11  in this disclosure are serviceable, the embodiment described in this disclosure is currently preferred. Comparison of the performance of prototypes of each embodiment has shown that the embodiment described in this disclosure demonstrated improved pressure retention in the seal created via compression of adapter  250  into receptacle  260 . Prototypes of each embodiment on 5.125″ internal diameter bores were pressure tested. In the embodiment disclosed in FIGS. 2 through 13 of 62/263,889 (and associated text), design was for about a 5,000 psi MAWP using a 7,500 psi test pressure. The ultimate destruction load was in fact just under 15,000 psi. In the embodiment described in this disclosure with reference to  FIGS. 2 through 11  herein, design was for about 10,000 psi MAWP with a 15,000 psi test load. Testing towards to ultimate destruction load was up to 17,500 psi without failure. 
     As has been described previously, the disclosed pressure control apparatus is available with a separate night cap option. Blocks  101 - 107  and  123  in method  100  on  FIG. 1  make reference to the night cap (when the night cap option is used), and are described in general in the disclosure above associated with  FIG. 1 .  FIGS. 12 and 13  illustrate release and engagement of the night cap (as described with reference to  FIG. 1 ) in more detail.  FIGS. 12 and 13  illustrate night cap  270  entering tulip  201  and preparing to be engaged on pressure control assembly  200 .  FIG. 12  illustrates engagement portion  271  on night cap  270 . Engagement portion  271  has functionally identical structure to that seen on adapter  250  on, for example,  FIG. 8 .  FIG. 8  illustrates shoulder  254 , seat surface  255  and slope surface  256  on adapter  250  interfacing with receptacle  260  on pressure control assembly  200  to provide a high pressure seal when cam locks  220  and locking ring  240  are engaged. Likewise, engagement portion  271  on  FIG. 12  provides functionally identical features on night cap  270  so that night cap  270  can engage with receptacle  260  in the same way as adapter  250  engages with receptacle  260 , via formation of a high pressure seal through engagement of cam locks  220  and locking ring  240 .  FIG. 13  depicts night cap secured into pressure control assembly  200  in the manner just described. 
     It will also be seen on  FIGS. 12 and 13  that night cap  270  advantageously provides a shackle or other conventional lifting attachment. This feature enables lifting apparatus (such as a crane) to attach to night cap  270  while secured in pressure control assembly  200 , providing a convenient hitch point and lifting connection for the entire pressure control apparatus. This feature thus facilitates, for example, lowering/raising of the entire apparatus during connection or disconnection from the well head, or between the wellhead and other transportation. 
       FIGS. 12 and 13  further depict vent line  400  provided in fitting F, as previously described above with reference to  FIG. 2 . In currently preferred embodiments, vent line  400  provides no internal mechanisms, and acts as a simple, conventional relief line with suitable connection fittings at either end (e.g. bolted flange, o-ring or threaded connection). Vent line  400  allows fluid under pressure in pressure control assembly  200  above wellhead W to be relieved and drained at such times as, for example, during removal of pressure control assembly  200  from wellhead W. 
       FIGS. 13 through 15  depict quick test ports  500  and associated manifold box  510  provided on pressure control assembly  200 .  FIG. 13  shows quick test ports  500  and manifold box  510  as seen from the outside of pressure control assembly  200 . A conventional high pressure hydraulic hose  515  connects manifold box  510  to one of the quick test ports  500 . As shown on  FIG. 13 , a conventional hydraulic hand pump  520 , preferably operated remotely, injects fluid into manifold box  510  under pressure, and then, via hose  515 , through to one of the quick test ports  500 . It will be appreciated that although  FIG. 13  illustrates a currently preferred embodiment in which two quick test ports  500  are provided. The scope of this disclosure is not limited in this regard, and any number may be provided. However, only one will be in operation at any time. Quick test ports  500  that are not in operation are sealed with threaded plugs for future use. The purpose of providing redundant quick test ports  500  is in case one or more become damaged during service, and have to be permanently sealed. In presently preferred embodiments, quick test ports  500  are preferably 1/16″ in diameter, although the scope of this disclosure is not limited in this regard. 
       FIG. 14  is a section as shown on  FIG. 12 , cutting through pressure control assembly  200  at the centerline elevation of quick test ports  500  (refer  FIG. 13 ).  FIG. 14  depicts quick test ports  500  providing fluid passageways from the outside of pressure control assembly  200  through to the interior of receptacle  260  along interior portion  261 . Quick test ports  500  further preferably provide fluid passageways to the interior of receptacle  260  at elevations between o-rings  252  when, as shown on  FIG. 10 , adapter  250  is fully compressed into receptacle  260  by cam locks  220  and the desired high pressure connection between adapter  250  and receptacle  260  is formed. 
     With continuing reference to  FIG. 10 , it will be seen that interior wall portion  261  of receptacle  260  engages adapter  250  between o-rings  252  when adapter  250  is received operationally into receptacle  260 . It will be further appreciated that when high pressure fluid is introduced from beneath receptacle  260 , the seals created by o-rings  252  will restrict or impede the ability of fluid to enter the engagement of adapter  250  with receptacle  260  along interior wall portion  261 . 
     Returning now to  FIGS. 13 and 14 , it will be seen that quick test port  500  enables fluid, pumped by hand pump  520  and delivered via manifold box  510  and hose  515 , to be introduced into the engagement of adapter  250  with receptacle  260  along interior wall portion  261 , thereby equalizing the pressure between o-rings  252  when high pressure fluid is introduced from beneath receptacle  260 . 
     Conversely, it will be appreciated that upon removal of adapter  250  from receptacle  260 , the seals created by o-rings  252  will restrict or impede the ability of fluid to depressurize in the engagement of adapter  250  with receptacle  260  along interior wall portion  261 . Quick test port  500  enables fluid trapped at pressure between o-rings  252  to be relieved. In other applications, fluid delivered by hand pump  520  through quick test port  500  enables the integrity of the seals provided by o-rings  252  to be checked prior to introducing high pressure fluid into the connection between adapter  250  and receptacle  260 . 
       FIG. 15  is a horizontal section through manifold box  510  illustrating more clearly the details shown in broken lines on, for example.  FIGS. 13 and 14 . Broadly, it will be appreciated that manifold  510  acts as a needle valve in the fluid line between hand pump  520  and quick test port  500 . This needle valve functionality acts as an added failsafe in the hydraulic line, so that pressure may be shut down in the event of an unintended leak during operations. Referring to  FIG. 15 , manifold box  510  comprises hand pump connection  511 . Hand pump connection  511  is conventional, and also provides conventional needle valve functionality which may be actuated to shut down pressure to or from manifold box  510  as required. Manifold box  510  also comprises a plurality of conventional hose connections  512 , each in internal fluid communication with hand pump connection  511 . As shown on  FIG. 13 , for example, hose  515  connects one of the hose connections  512  to quick test port  500 . Hose connections  512  not in use may be sealed using a conventional threaded plug. 
     Earlier description made clear that the scope of this disclosure in no way limits the disclosed pressure control apparatus to specific sizes or models. Currently envisaged embodiments make the apparatus available in several sizes, shapes, and pressure ratings to adapt to existing surface pressure control equipment. Proprietary connections may require specialized adapters. It will be nonetheless understood that the scope of this disclosure is not limited to any particular sizes, shapes, and pressure ratings for various embodiments of the disclosed pressure control apparatus, and that the embodiments described in this disclosure and in U.S. provisional patent application Ser. No. 62/263,889 (incorporated herein by reference) are exemplary only. 
     For example, other embodiments may provide a smaller apparatus, having all the functionality of the disclosed pressure control apparatus embodiments disclosed in detail herein, except with a smaller overall diameter, and correspondingly fewer cam lock assemblies around the periphery. In other embodiments, the pressure control apparatus may provide wedge mechanisms instead of cam lock mechanisms to enable, compress and hold the pressure connection. In yet other embodiments, spring assemblies may supplement the mechanisms compressing and holding the pressure connection. 
     Currently envisaged embodiments of the disclosed pressure control apparatus may provide pressure ratings including 5,000 psi, 10,000 psi and 15,000 psi MAWP ratings, each further rated for H 2 S service. Currently envisaged sizes may range from about 2″ to about 7″ ID. The foregoing sizes and performance metrics are exemplary only, and the scope of this disclosure is not limited in such regards. It will be appreciated that the number of cam locks and associated linkages/pistons will change with diameter. 
     Although the pressure control apparatus has been described in this disclosure with reference to an exemplary application in pressure control at a wellhead, alternative applications could include, for example, areas such as deep core drilling, offshore drilling, methane drilling, open hole applications, hydraulic fracturing, wireline operations, coil tubing operations, mining operations, and various operations where connections are needed under a suspended or inaccessible load (i.e., underwater, hazardous area). 
     Exemplary materials used in the construction of the disclosed pressure control apparatus include high strength alloy steels, high strength polymers, and various grades of elastomers. 
     Although the inventive material in this disclosure has been described in detail along with some of its technical advantages, it will be understood that various changes, substitutions and alternations may be made to the detailed embodiments without departing from the broader spirit and scope of such inventive material as set forth in the following claims.

Summary:
A wellhead pressure control fitting comprising a generally tubular Pressure Control Equipment (PCE) adapter configured to mate with pressure control equipment at a first adapter end, and with a receptacle inside a generally tubular pressure control assembly at a second adapter end. The pressure control assembly is configured to mate with a wellhead. Cooperating abutment surfaces form a high pressure seal when the second adapter end is compressively received into the receptacle. A plurality of cam locks on the exterior of the pressure control assembly rotate responsive to extension and retraction of the cam lock pistons. Cam lock rotation causes perimeter curvatures on the cam locks to bear down on corresponding curvatures on the second adapter end, which in turn compresses the second adapter end into the receptacle to form the seal. A locking ring may restrain the cam locks from rotation while the seal is enabled.