FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to a modular locking and retaining mechanical design solution to reliably secure immersed, unrestrained and un-powered objects in a fluid environment to a fixed support surface such as a mounting frame or panel, with a quick connect/disconnect engagement method by a diver (i.e. manual mate) or remote-operated vehicles (ROVs) mate, into a fixed mounting frame or panel installed at a subsea deployed platform for oil and gas offshore applications. 
       BACKGROUND OF THE INVENTION 
       [0002]    In offshore drilling and production operations, equipment are often subjected to harsh conditions thousands of feet under the sea surface with working temperatures of −50° F. to 350° F. with pressures of up to 15,000 psi. Subsea control and monitoring equipment commonly are used in connection with operations concerning the flow of fluid, typically oil or gas, out of a well. Flow lines are connected between subsea wells and production facilities, such as a floating platform or a storage ship or barge. Subsea equipment include sensors and monitoring devices (such as pressure, temperature, corrosion, erosion, sand detection, flow rate, flow composition, valve and choke position feedback), and additional connection points for devices such as down hole pressure and temperature transducers. A typical control system monitors, measures, and responds based on sensor inputs and outputs control signals to control subsea devices. For example, a control system attached to a subsea tree controls down-hole safety valves. Functional and operational requirements of subsea equipment have become increasingly complex along with the sensing and monitoring equipment and control systems used to insure proper operation. 
         [0003]    To connect the numerous and various sensing, monitoring and control equipment necessary to operate subsea equipment, harsh-environment connectors are used with electrical cables, optical fiber cables, or hybrid electro-optical cables. Initial demand for subsea connector development was in connection with military applications. Over time demand for such connectors has grown in connection with offshore oil industry applications. 
         [0004]    Early underwater connectors were electrical “dry-mate” devices, intended to be mated prior to immersion in the sea and were of two principal types: rubber-molded “interference fit” type and rigid-shell connectors. The rubber molded “interference-fit” connectors depended on receptacles with elastic bores that stretched and sealed over mating plugs. The rigid-shell connectors had mating parts sealed together via O-rings or other annular seals. 
         [0005]    Ocean Design, Inc. has been an industry leader in the development of subsea connectors and applications. Dr. James Cairns&#39; article Hybrid Wet-Mate Connectors: ‘Writing the Next Chapter’, Sea Technology, published July 1997, provides a thorough discussion of the history of underwater connectors through to 1997, and is a source for this background summary. In the early 1960s, electrical connectors intended for mating and de-mating underwater came into use. These so called “wet-mate” connectors were adaptations of the interference-fit dry-mate versions, and were designed so that when mated, the water contained in the receptacle bores would be substantially expelled prior to sealing. Also during this time, the first oil-filled and pressure-balanced electrical connector designs were introduced. These isolated the receptacle contacts within sealed oil-chambers which, during engagement, were penetrated by elongated pins with insulated shafts. Connection was, therefore, accomplished in the benign oil, not in harsh seawater. Unlike previous connector types which could not be disengaged at even modest depths, pressure balancing type connectors could be actuated anywhere in the sea. These wet-mate oil-filled connectors eventually became the high-reliability standard for the offshore oil industry. One critical design element of oil-filled connectors is providing seals that allow the oil chambers to be penetrated repeatedly without losing the oil or allowing seawater intrusion. One design widely used for electrical applications accomplishes this through the use of dielectric pistons, one of which resides in each receptacle socket. Each piston has a spring which biases it outward to automatically fill the socket&#39;s end-seal when the plug pin is withdrawn. During mating the pins push these pistons back through the oil-chamber ports (which they have kept sealed) and onward deep inside the sockets. 
         [0006]    Early subsea wet-mate optical connectors passed only one optical circuit and used expanded-beam lenses or fiber-to-fiber physical contact junctions. To protect the optical interfaces, both the plug and receptacle contacts were housed in oil-filled chambers which were pressure balanced to the environment. Problems with this design included that sealing and cleanliness were not adequate to provide desired reliability. The spring/piston concept used for sealing electrical connectors is not effective for optical connectors as pistons get in the way of the light path. A second type of subsea-mateable optical connector consisted basically of dry-mate connectors which had a bit of optical index-matching gel placed in the contact interfaces. The excess gel was expelled upon mating. There was no attempt to exclude sand or silt from the interfaces, and the resulting performance was left to chance. Hybrid wet-mate devices were an attempt to combine oil-filled and pressure-balanced plug and receptacle housings with means for sealing and maintaining cleanliness of the optical interfaces. Within both, plug and receptacle, oil chambers, groups of contact junctions are aligned behind cylindrical rubber face-seals. When mated, opposed plug and receptacle seals first press against each other like the wringers of an old-fashioned washing machine, forcing the water out from between them. As the mating sequence continues the opposed plug and receptacle seals, like the wringers, roll in unison and transport any debris trapped between them off to the side. The action simultaneously causes clean, sealed, oil-filled passages to open between opposed plug and receptacle contact junctions. Continuing the mating process, plug pins advance through the sealed passages to contact sockets within the receptacle. De-mating is the reverse sequence. In the case of electrical circuits each mated pin/socket junction is contained in an individual, secondary, sealed oil chamber within the common oil volume. The contacts are unexposed to environmental conditions before, during and after mating. 
         [0007]    There are many types of connectors for making electrical and fiber-optic cable connections in hostile or harsh environments, such as undersea or submersible connectors which can be repeatedly mated and de-mated underwater at great ocean depths. Current underwater connectors typically comprise releasably mateable plug and receptacle units, each containing one or more electrical or optical contacts or junctions for engagement with the junctions in the other unit when the two units are mated together. Each of the plug and receptacle units or connector parts is attached to cables or other devices intended to be joined by the connectors to form completed circuits. To completely isolate the contacts to be joined from the ambient environment, one or both halves of these connectors house the contacts in oil-filled, pressure-balanced chambers—this is referred to as a pressure balanced set-up. Such devices are often referred to as “wet-mate” devices and often are at such great depths that temperature and other environmental factors present extreme conditions for materials used in such devices. The contacts on one side (plug) are in the form of pins or probes, while the contacts or junctions on the other side (receptacle) are in the form of sockets for receiving the probes. 
         [0008]    Typically, the socket contacts are contained in a sealed chamber containing a dielectric fluid or other mobile substance, and the probes enter the chamber via one or more sealed openings. Such wet-mate devices have previously been pressure compensated. One major problem in designing such pressure compensated or pressure balanced units is the performance and longevity of seals required to exclude seawater and/or contaminates from the contact chamber after repeated mating and de-mating. 
         [0009]    Both the plug and receptacle halves of most fiber-optical connectors which are mateable in a harsh environment have oil-filled chambers. The chambers are typically brought face-to-face during an early step of the mating sequence. In a subsequent mating step, one or more connective passages, sealed from the outside environment, are created between the chambers of the mating connector halves. The passages join the two oil-filled chambers, creating a single, connected oil volume. Actual connection of the contact junctions then takes place within the common oil chamber. Examples of prior pressure compensated wet-mate devices are described in U.S. Pat. Nos. 4,616,900; 4,682,848; 5,838,857; 6,315,461; 6,736,545; and 7,695,301. 
         [0010]    In some known underwater electrical connectors, such as that described in U.S. Pat. Nos. 4,795,359 and 5,194,012 of Cairns, tubular socket contacts are provided in the receptacle unit, and spring-biased pistons are urged into sealing engagement with the open ends of the socket assemblies. As the plug and receptacle units are mated, pins on the plug portion urge the pistons back past the contact bands in the sockets, so that electrical contact is made. However, this type of arrangement cannot be used in a straightforward way for an optical connector since the optical contacts must be able to engage axially for practical purposes. 
         [0011]    U.S. Pat. No. 4,666,242 of Cairns describes an underwater electro-optical connector in which the male and female connector units are both oil filled and pressure balanced. This device utilizes a penetrable seal element having an opening which pinches closed when the units are separated and seals against the entering probe when mated. Other known fiber-optic connectors have similar seals which are not suitable for use under some conditions and may tend to lose effectiveness after repeated mating and de-mating. 
         [0012]    Other known seal mechanisms involve some type of rotating seal element along with an actuator for rotating the seal element between a closed, sealed position when the units are unmated, and an open position when the units are mated, allowing the contact probes to pass through the seal elements into the contact chambers. Such connectors are described, for example, in U.S. Pat. Nos. 5,685,727 and 5,738,535 of Cairns. These overcome some of the reliability problems of penetrable seals, for example, but can be too complex for miniaturized connectors. 
         [0013]    Most existing wet-mate connectors of the pressure compensation-type depend on elastomers, which have several known disadvantages and which only grow as required temperature and pressure performance in the operating environments increase. Above 350° F. in particular, but at lower temperatures as well, elastomers in seawater degrade rapidly, and can fail due to numerous causes, including: rupture; rapid gas decompression (RGD) embolisms; leakage; melting; and gas permeation. Materials science has advanced to create new materials capable of functioning and lasting in harsher environments, but the industry is moving towards temperature regimes at or in excess of 400° F., where even the newest materials will be stressed to or beyond their limits. 
         [0014]    Other pressure compensation systems typically rely on metal bellows, which have different weaknesses. At the scale of ever-smaller optical feedthrough systems, where diameters of compensation systems are typically less than an inch, the metal of the bellows are extraordinarily thin, and the welded joints may be subject to fatigue, opening up failure pathways similar to those of elastomers. One primary concern with deployable embodiments of wet-mate devices regarding pressure compensation is the use of elastomeric hoses. Operators experience signal loss on gas and gas-lift wells during start up and shutdown. At these events the gas functions in the well are dynamic and not at equilibrium. In addition, pressure compensated systems in gaseous environments have experienced complete loss of pressure compensation and infiltration of seawater into spaces that should be dielectrically insulated by oil. 
         [0015]    Thus, common underwater connectors comprise releasably, mateable plug and receptacle units, each containing one or more electrical or optical contacts or junctions for engagement with the junctions in the other unit when the two units are mated together. The contacts on one side are in the form of pins or probes, while the contacts or junctions on the other side are in the form of sockets for receiving the probes. Typically, the socket contacts are contained in a sealed chamber containing a dielectric fluid or other mobile substance, and the probes enter the chamber via one or more sealed openings. One major problem in designing such units is the provision of seals which will adequately exclude or evacuate seawater and/or contaminants from the contact chamber after repeated mating and de-mating operations. 
         [0016]    There are many types of housings and frames for mounting or securing modular connectorized distribution units (MCDUs) in a fluid environment. These housings secure the MCDUs which are subsea distribution units which may provide oil-filled, pressure-balanced, connectorized junctions for flexible underwater mating for a variety of wet mate connectors. An MCDU functions as the hub of an expandable subsea network. The MCDUs may be used to join multiple circuits of optical, electrical, or hybrid connection type configurations. The MCDU is designed to interface with a variety of subsea structures. 
         [0017]    MCDUs are typically installed on a housing or landing frame on the surface prior to being secured in a sub-sea environment. MCDU landing frames are typically installed on concrete slabs or attached to larger sub-sea structures. These MCDUs and MCDU landing frames may have originally been designed and intended to withstand 20-25 years in a corrosive, turbid environment. However, in normal applications, MCDUs may need to be removed for refurbishment or repair after only 5-8 years as a result of factors including galvanic corrosion. 
         [0018]    Furthermore, MCDUs and other sub-sea devices may need to be moved from their original location or removed entirely due to factors other than equipment failure. For example, a planned oil well may not be economically feasible due to the oil reserve not being as large as originally surveyed. Also, in the field of sub-sea mining, equipment may need to be moved or replaced more frequently as a seam of minerals or ore is surveyed and mined. Sub-sea mining equipment also may require more power than sub-sea oil drilling equipment and may therefore put additional strain on equipment such as MCDUs, requiring more frequent refurbishment or repair. 
         [0019]    Typically, when an MCDU needs to be replaced or removed, removal is difficult because of the buildup of silt and other particulates and because of galvanic corrosion. These and other factors may make it hard if not impossible to remove an MCDU from its landing frame, resulting in the inability to remove, reuse, or refurbish either the frame or the MCDU. Refurbishing an MCDU is economically desirable over replacing and MCDU due to the very high equipment cost per MCDU. Removing and refurbishing an MCDU also eliminates the need to install a new landing frame or remove existing landing frames that may not be able to be separated from an MCDU using existing securing methods. 
         [0020]    Additionally, when connecting various wet-mate type connectors to or from an MCDU, problems exist in securing connectors, cables, remote operate vehicles (ROVs), and other materials. Currently there exists no method for securing immersed, un-restrained objects in seawater or freshwater with vertical stability and a positive meta-centric height to a fixed structure, neutralizing the buoyancy force effect. 
         [0021]    What is needed is a system for the maintaining of a secured, consistent, stably removable MCDU housing position into a landing base frame to facilitate a reliable mating/de-mating alignment capability with connector harnesses by manual (i.e. diver) mating or by a remote-operated vehicle (ROV) mating methods. 
       SUMMARY OF THE INVENTION 
       [0022]    Embodiments described herein provide a new modular securing device for ROV and diver mate-able subsea applications. 
         [0023]    The present invention comprises a modular and versatile mechanical design that provides a quick, reliable and low-cost solution to secure immersed, un-restrained objects in seawater or freshwater with vertical stability and a positive meta-centric height to a fixed structure, neutralizing the buoyancy force effect. The present invention also reduces the risk of mating and/or de-mating connectors and reduces the probability of misalignments which may result in unreliable and costly failures for the subsea applications. 
         [0024]    The present invention provides a T-handle locking key and T-handle ACME threaded shaft/stud assembly for securing an MCDU and removable parking plate to an MCDU landing unit. Use of the quick disconnect T-handle locking key and threaded T-handle body and stud assemblies for attaching an MCDU to an MCDU landing frame provides the benefit of easy and quick removal or replacement of an MCDU or parking plate. The modular securing devices may be operated either manually by a diver or remotely by an ROV. The modular securing devices according to the present invention may also be used in other configurations and with other frames, structures, or devices as a method of securing one apparatus to another in a sub-sea environment. 
         [0025]    In one embodiment, the present invention comprises a modular securing device comprising: a frame having a base, a top, and a body, said body having a front, a back, and extending vertically from said bottom to said top and having a hollow central area and an opening extending the length of the front; a locking key assembly comprising: a locking key comprising: an elongated body having a front end, a back end, and an exterior surface; a t-shaped handle attached to said back end; a raised protrusion extending vertically from said exterior surface at said front end; a spring assembly comprising a tension spring disposed on the elongated body intermediate an inner plate and an outer plate, and said spring surrounding said elongated body between said inner plate and said outer plate; and a set of bushings having a front face and a back face, and a central bore, said back face attached to said frame, said set of bushings adapted to receive said front end of said elongated body and having a guide channel adapted to guide said raised protrusion of said locking key when receiving said front end of said elongated body, and a recess formed therein for receiving the raised protrusion; whereby with said locking key introduced into said frame said t-shaped handle is adapted to be pushed forward to compress said tension spring between said inner and outer plates and to cause the raised protrusion to extend outward from the guide channel, said locking key adapted to rotate to lock in a fixed position with said raised protrusion engaging the recess, thereby securing a modular connection unit received in the frame central hollow area in place. 
         [0026]    The above embodiment may further comprise wherein the locking key assembly is located at said top of said frame and is adapted to permit said locking key to pass through said frame. The locking key may be attached to said frame by a flexible securing means. The flexible securing means may be a braided cable. The set of bushings may comprise a first bushing and a second bushing. The set of bushings may have a set of indentations on said front of said bushings adapted to secure said raised protrusion of said locking key. The modular securing device may further comprise a set of threaded securing assemblies comprising: a cylindrical stud assembly having a top and a bottom, and a body extending from said bottom to said top, said body having an exterior, said exterior having a threaded portion; and a cylindrical handle assembly having a top and a bottom, a body extending from said top to said bottom, said bottom having an opening, said body having a hollow interior threaded portion, and a handle attached to said top. The cylindrical stud assembly threaded portion and said cylindrical handle assembly hollow threaded portion may comprise ACME threading. The locking key assembly and said set of threaded securing assemblies may be comprised of a material resistant to galvanic corrosion. The body of said cylindrical stud assembly and said body of said cylindrical handle assembly may be comprised of brass. The frame may be adapted to receive a modular connectorized distribution unit (MCDU). The frame may further comprise a mounting assembly, said mounting assembly having a front and a back, and a first side and a second side, said first side attached to the frame and said mounting assembly extending outwardly from the frame. 
         [0027]    In another embodiment, the present invention may comprise a modular securing apparatus comprising: a locking key assembly comprising: an elongated locking key body with a first and a second end and having a handle on said first end and a raised protrusion on said second end; said elongated locking key assembly having a spring assembly at said first end, said spring assembly comprising a spring, an inner spring plate, and an outer spring plate; a set of bushings adapted to receive said elongated locking key assembly and said raised protrusion and having a set of locking indentations; and wherein said spring assembly is adapted to compress to allow said raised protrusion to pass through said set of bushings and is further adapted to secure said raised protrusion in one of said set of locking indentations. 
         [0028]    The above embodiment may further comprise wherein the modular securing apparatus further comprises a set of threaded securing assemblies comprising: a body portion having an exterior threaded portion; and a handle portion having an interior threaded portion and adapted to receive said body portion. The modular securing apparatus may further comprise a frame having a base, a top, and a body, said body having a hollow central area and an exterior surface; wherein elongated locking key assembly is disposed near said top of said frame; and wherein said threaded securing assemblies are disposed on the exterior surface. The elongated locking key assembly may be located at said top of said frame and is adapted to permit said locking key body to pass through said frame. The locking key may be attached to said frame by a flexible securing means. The flexible securing means may be a braided cable. The set of bushings may comprise a first bushing and a second bushing. The set of bushings may have a set of indentations on said front of said bushings adapted to secure said raised protrusions of said locking key. The body threaded portion and said handle interior threaded portion may comprise ACME threading. The locking key assembly and said set of threaded securing assemblies may be comprised of a material resistant to galvanic corrosion. The body of said cylindrical stud assembly and said body of said cylindrical handle assembly are comprised of brass. The frame may be adapted to receive a modular connectorized distribution unit (MCDU). The frame may further comprise a mounting assembly, said mounting assembly having a front and a back, and a first side and a second side, said first side disposed on said frame exterior and said mounting assembly extending outwardly from said frame. The threaded securing assemblies may be disposed on said front of said mounting assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    In order to facilitate a complete understanding of the present invention, this system, and the terms used, reference is now made to the accompanying drawings, in which like elements are referenced with like numerals. These drawings should not be construed as limiting the present invention or system, but are exemplary and for reference. 
           [0030]      FIG. 1  provides a perspective view of an embodiment of the modular securing device according to the present invention; 
           [0031]      FIG. 2  provides a reverse angle perspective view of an embodiment of the modular securing device according to the present invention; 
           [0032]      FIG. 3  provides a perspective view of an embodiment of a T-handle locking key and fixed holding bushings according to the present invention; 
           [0033]      FIG. 4  provides a perspective view of an embodiment of a T-handle locking key with a cutaway view of the fixed holding bushings according to the present invention; 
           [0034]      FIG. 5  provides another a perspective view of an embodiment of a T-handle locking key according to the present invention; 
           [0035]      FIG. 6  provides a detailed perspective view of an embodiment of the upper section of a modular securing device according to the present invention; 
           [0036]      FIG. 7  provides a detailed top perspective view of an embodiment of the upper section of a modular securing device according to the present invention; 
           [0037]      FIG. 8  provides a plan view of an embodiment of the upper section of a modular securing device according to the present invention; 
           [0038]      FIG. 9  provides a detailed cutaway top perspective view of an embodiment of the upper section of a modular securing device including the T-handle locking key according to the present invention; 
           [0039]      FIG. 10  provides a detailed perspective view of an embodiment of the upper section of a modular securing device and the handle of the T-handle locking key with a cutaway view of the fixed holding bushing according to the present invention; 
           [0040]      FIG. 11  provides a detailed cutaway view of an embodiment of a T-handle retain ACME threaded shaft and ACME threaded stud assembly according to the present invention; 
           [0041]      FIG. 12  provides a detailed perspective view of an embodiment of the upper section of a modular securing device, ACME threaded T-handle shaft and ACME threaded stud assembly according to the present invention; 
           [0042]      FIG. 13  provides a detailed cutaway perspective view of an embodiment of the upper section of a modular securing device, ACME threaded T-handle shaft and ACME threaded stud assembly, and T-handle locking key according to the present invention; 
           [0043]      FIG. 14  provides a detailed perspective view of an embodiment of an upper and lower ACME threaded T-handle shaft and ACME threaded stud assembly according to the present invention; 
           [0044]      FIG. 15  provides a perspective view of an embodiment of the modular securing device with attached parking plate according to the present invention; and 
           [0045]      FIGS. 16-17  provide perspective views of prior art MCDU landing frames that may be modified according to the present invention. 
           [0046]      FIGS. 18A and 18B  provide front and rear perspective views of an alternate embodiment of the present invention in an ROV operable configuration. 
       
    
    
     DETAILED DESCRIPTION 
       [0047]    The present invention and system will now be described in more detail with reference to exemplary embodiments as shown in the accompanying drawings. While the present invention and system is described herein with reference to the exemplary embodiments, it should be understood that the present invention and system is not limited to such exemplary embodiments. Those possessing ordinary skill in the art and having access to the teachings herein will recognize additional implementations, modifications, and embodiments as well as other applications for use of the invention and system, which are fully contemplated herein as within the scope of the present invention and system as disclosed and claimed herein, and with respect to which the present invention and system could be of significant utility. 
         [0048]    Certain embodiments as disclosed herein provide for a modular securing device for ROV and diver mate-able subsea applications in which a single T-handle locking key is attached to the upper portion of an MCDU landing frame and a pair of ACME threaded T-handle shaft/stud assemblies are attached to protrusions on the side of the MCDU landing frame. In one embodiment, the upper and a lower ACME threaded T-handle shaft/stud assemblies are attached to respective upper and lower protrusions on the MCDU frame. 
         [0049]    The drawings illustrate exemplary embodiments of methods and apparatuses for securing items, connections, frames, or assemblies to an MCDU landing frame in a turbid fluid environment, using a combination of T-handle locking keys and ACME threaded T-handle shaft/stud assemblies. 
         [0050]    With reference now to  FIG. 1 , a perspective view of a first exemplary embodiment of the modular securing device  100  according to the present invention is provided. The modular securing device  100  comprises the MCDU landing frame  150 , removable parking plate mounting frame  350 , base  110 , and upper frame portion  120 . A T-handle locking key  200  is mounted below the upper frame portion  120  and extends horizontally through the body of the MCDU landing frame  150 . An ACME threaded T-handle shaft/stud assembly  300  and a lower ACME threaded T-handle shaft/stud assembly  320  are mounted on the upper portion and lower portion of the removable parking plate mounting frame  350  respectively. 
         [0051]    With reference now to  FIG. 2 , a reverse angle perspective view of an embodiment of the modular securing device  100  is provided. The handle of the T-handle locking key  200  can be seen extending from the exterior of the MCDU landing base/frame  150  below the upper frame portion  120 . The ACME threaded T-handle shaft/stud assembly  300  and a lower ACME threaded T-handle shaft/stud assembly  320  on the removable parking plate mounting frame  350  extend out from the parking plate mounting frame  350  towards the front of the modular securing device  100 . The base  110  may be used to mount the modular securing device  100  to any subsea structure. 
         [0052]    With reference now to  FIGS. 3 and 4 , a perspective view of an exemplary embodiment of a T-handle locking key  200  is provided. The T-handle locking key  200  with T-handle  212 , and T-handle shaft  210  is shown with a pair of fixed holding bushings  220  and  221 . An attaching device or lanyard  240 , which may be at a securing device attachment point  242 , a lanyard, cord, braided cable, wire, rope, or other suitable material, is attached to the T-handle  212  and, as shown in  FIG. 2 , also to the body of the MCDU frame  150  to prevent the T-handle locking key  200  from drifting away when not in an engaged and locked state. 
         [0053]    With T-handle locking key  200  in place, the first fixed holding bushing  220  and second fixed holding bushing  221  are mounted on opposite lateral sides of the MCDU landing base/frame  150 . Each of the fixed holding bushings  220  and  221  may comprise a quick-alignment slot  222 B and  222 A, respectively, at the top of the bushing and a pair of locking indentations  224  oriented along the horizontal axis of the bushing. The quick-alignment slots  222 A and  222 B guide the quick-alignment keyed pin  214  of the T-handle locking key  200  through the each of the bushings  220  and  221 . After being inserted through both bushings  220  and  221  and clearing the exterior surface of fixed holding bushing  220 , the T-handle locking key  200  and quick-alignment keyed pin  214  may be rotated ninety degrees clockwise or counter-clockwise to lock the quick-alignment keyed pin  214  into either of the locking indentations  224 . 
         [0054]    The quick-alignment keyed pin  214  is held into a locking indentation  224  by a compression spring force exerted by the tension spring  230 . The tension spring  230  exerts a spring force along the length of the T-handle locking key  200  by pressing on both of the outer spring plate  232  and inner spring plate  234 . The outer spring plate  232  and inner spring plate  234  keep the tension spring  230  in position and when the T-handle locking key  200  is inserted fully through both of the fixed holding bushings  220  and  221  the exterior of the second fixed holding bushing  221  facing the inner spring plate  234  contacts the inner spring plate  234  and moves the plate  234  along the axis of the T-handle shaft  210  towards the T-handle  212 . This movement compresses the tension spring  230  which causes a low torque spring force to hold the quick-alignment keyed pin  214  in place in the locking indention  224  of the fixed holding bushing  220 . 
         [0055]    The compression spring force principle is used in combination with a low torque and a mechanically keyed drive alignment design fixture to assure a quick connect/disconnect. This design provides a reliable and secure locking capability to neutralize the buoyancy effect from the Archimedes principle of buoyancy of objects immersed in a fluid. The design also utilizes the material compatibility to avoid galvanic corrosion effect from dissimilar materials in contact with each other, and immersed in an electrolytic solution such as seawater. All components of the T-handle locking key  200  and ACME threaded T-handle shaft/stud assembly  300  may be made in similar fashion and from compatible materials which include 316 and 316L SST, and a bronze (anti-friction material) for marine and subsea applications. 
         [0056]    With reference now to  FIG. 4 , a perspective view of an embodiment of T-handle locking key  200  with a cutaway view of the fixed holding bushings  220  and  221  is provided. The T-handle locking key  200  is shown inserted through bushing  221  and partially through bushing  220 . At this point, the quick-alignment keyed pin  214  has not cleared the exterior of the bushing  220  and is still in the quick-alignment slot  222 B. It can be seen that the portion of the T-handle shaft  210  that the keyed alignment pin  214  is fixed to is of a smaller radius and circumference than the rest of the T-handle shaft  210 . If manually operated or operated by a ROV, the T-handle  212  would need to be further depressed towards the bushing  221  to allow the quick-alignment keyed pin  214  to clear the bushing  220  so that the T-handle locking key  200  could be rotated ninety degrees clockwise or counter-clockwise to secure the quick-alignment pin  214  in one of the locking indentations  224 . 
         [0057]    With reference now to  FIG. 5 , a perspective view of an embodiment of T-handle locking key  200  is provided. The tension spring  230  around the T-handle body  210  can be seen held in place by the inner spring plate  234 . In operation, the inner spring plate  234  compresses the tension spring  230  which then exerts a compression spring force along the axis of the T-handle body  210 . This force will put pressure on the quick-alignment keyed pin  214  that will retain the quick-alignment keyed pin  214  in a locking indentation  224  until a reverse operation occurs. The T-handle  212  is attached to the T-handle body  210  via an attaching means  216  which may be any of screw, bolt, hex screw, locking screw, or similar suitable attaching means. 
         [0058]    With reference now to  FIG. 6  a detailed perspective view of an embodiment of the upper section of the modular securing device  100  is provided. In this view, the T-handle locking key  200  is inserted, e.g., via a bushing, in the frame of the MCDU landing base/frame  150  below the upper frame portion  120 . On the opposite side of the T-handle locking key  200  is the upper ACME threaded T-handle shaft/stud assembly  300  which is secured to the ACME threaded stud  310  which is in turn formed in or attached to the removable parking plate frame  350 . The ACME threaded T-handle shaft/stud assembly  300  is used to releaseably attach a parking plate to the MCDU landing base frame  150 . The ACME threaded T-handle shaft/stud assembly  300  may be comprised of brass or another low friction material that assures quick, reliable, and secure engagement and disengagement. 
         [0059]    With reference now to  FIG. 7 , a detailed top perspective view of an embodiment of the upper section of the modular securing device  100  is provided. The T-handle body  210  is seen extended through the length of the interior space of the MCDU landing frame  150 . The MCDU landing frame  150  may be an elongated rectangular or other suitable shape with a hollow interior portion and at least one opening on one side of the frame  150 . The T-handle body  210  would secure an MCDU placed in the MCDU landing frame  150  and would keep the MCDU in place when in operation or until the MCDU is more permanently but releasably secured in the MCDU landing frame  150  by bolts, screws, or other suitable fastening means. The fixed holding bushing  220  can be seen on the exterior of the MCDU landing frame  150 , a similar bushing  221  would be mounted on the opposite exterior surface of the MCDU landing frame  150 . The quick-alignment pin  214  is in the quick-alignment slot  222 B, indicating that the pin is not fully engaged and locked in the locking indentations  224 . The ACME threaded T-handle shaft/stud assembly  300  with ACME threaded T-handle body  302  is shown secured to the stud portion of the assembly on the removable parking plate frame  350 . 
         [0060]    With reference now to  FIG. 8 , a plan view of an embodiment of the upper section of a modular securing device is provided. The T-handle body  210  is shown extending through the fixed holding bushing  221 , the central area  152 , and the fixed holding bushing  220  of the modular securing device  100 . In operation, an MCDU would be secured by the T-handle locking key  200  in the central area  152  with MCDU connectors facing towards the opening  154 . To lock the T-handle locking key  200 , the T-handle  212  would be depressed inwardly towards the fixed holding bushings  221  and  220 , compressing the spring  230  between the plates  232  and  234 . This inward force would extend the quick-alignment pin  214  beyond the fixed holding bushing  220  so that the pin  214  and T-handle locking key  200  could be rotated by a force on the T-handle  212  into a locked position. In an unlocked and removed position, the T-handle locking key  200  is secured to the MCDU landing frame  150  by the lanyard  240 . The upper frame portion  120  is angled or sloped down and inwardly towards the central area  152  to facilitate installation and removal of an MCDU. 
         [0061]    With reference now to  FIG. 9 , a partial detailed cutaway top perspective view of an embodiment of the upper section of a modular securing device  100  including the T-handle locking key  200  is provided. The T-handle locking key  200  is in an inserted but not locked position. The body  210  extends through the central area  152  of the modular securing device  100  and the T-handle  212  is in a horizontal orientation. The quick-alignment pin  214  is in the quick-alignment slot  222 B and not locked into one of the locking indentations  224 B. When locked, the T-handle  212  would be rotated, in this example, into a vertical orientation by rotating the handle  212  ninety degrees clockwise or counter clockwise after depressing the handle inwardly towards the MCDU landing frame  150 . This inward force and subsequent rotation would cause the quick-alignment pin  214  to first extend out from the fixed bushing  220  and then to rotate from the quick-alignment slot  222 B into one of the locking indentations  224 B. 
         [0062]    With reference now to  FIG. 10 , a partial detailed perspective view of an embodiment of the upper section of a modular securing device  100  and the handle of the T-handle locking key  200  with a cutaway view of the fixed holding bushing  221  is provided. In the unlocked state, shown, the T-handle  212  is in a horizontal orientation and the T-handle body  210  is inside the fixed holding bushing  221 . To lock, the T-handle  212 , attached to the T-handle body  210  by screw  216 , is first depressed inwardly. This inward depression exerts a force against the biasing force of the tension spring  230 . The tension spring  230  is compressed between the inner spring plate  232  and outer spring plate  234 . When the spring  230  is fully compressed and the quick-alignment pin  214  extends beyond the fixed holding bushing  220 , shown in  FIG. 9 , the T-handle  212  may be rotated into a vertical or locked position. When the inward depression force on the T-handle  212  is released, the biasing force of the spring  230  locks the quick-alignment pin  214  into place in the locking indentations  224 B. 
         [0063]    With reference now to  FIG. 11 , a detailed cutaway view of an embodiment of a T-handle retain ACME threaded shaft/stud assembly  300  is provided. The T-handle ACME threaded shaft/stud assembly  300  comprises the handle assembly  301  and the stud assembly  310 . The handle  304  is connected to the handle body  302  by the handle extension  306 . The handle body  302  has a hollow threaded interior  308 . The hollow threaded interior  308  may be ACME threaded, or threaded in any other suitable manner. The threads in the hollow threaded interior  308  correspond to threads on the threaded portion  312  of the stud assembly  310 . The threaded portion  312  is raised from the base  313  of the stud assembly  310  and is separated from the base  313  by the spacer  311 . When in use, the body  302  of the handle assembly  301  secures a parking plate to the parking frame  350  (shown in  FIG. 12 ) on the spacer  311  between the body  302  and the base  313  through a force exerted by tightening the handle  304  on the threads of the threaded portion  312 . The handle assembly  301  may be secured to the parking frame  350  by a lanyard  314  or other suitable securing means. The handle assembly  301  and stud assembly  310  may be made of brass or other suitable material that is resistant to corrosive and high pressure environments, is resistant to galvanic corrosion, and has a low coefficient of friction. 
         [0064]    With reference now to  FIG. 12 , a detailed perspective view of an embodiment of the upper section of a modular securing device  100 , ACME threaded T-handle shaft  301  and ACME threaded stud assembly  310  is provided. The stud assembly  310  is secured to the parking plate frame  350 . The stud assembly  310  may be welded to the parking plate frame  350  or secured by other suitable securing means such as by a corrosion resistant bolt. The body  302  of the handle assembly  301  is secured on the threads of the stud assembly  310 . The handle assembly  301  may be loosened by rotating the handle  304  in a counter-clockwise motion or tightened by rotating the handle in a clockwise motion about the stud assembly  310 . 
         [0065]    With reference now to  FIG. 13 , a detailed cutaway perspective view of an embodiment of the upper section of a modular securing device  100 , ACME threaded T-handle shaft  301  and ACME threaded stud assembly  310 , and T-handle locking key  200  is provided. The parking plate frame  350  is attached to the side of the MCDU landing base/frame  150 . The T-handle locking key  200  is inserted into the MCDU landing frame  150  and the T-handle threaded shaft/stud assembly  300  is attached to the parking plate frame  350 . The body  302  of the handle assembly  301  is threaded onto the stud assembly  310 . 
         [0066]    With reference now to  FIG. 14 , a detailed perspective view of an embodiment of an upper and lower ACME threaded T-handle shaft and ACME threaded stud assembly,  300  and  320  respectively, attached to a parking plate frame  350  is provided. The upper T-handle assembly  300  and lower T-handle assembly  320  may secure a parking positions plate (such as parking positions plate  1502  of  FIG. 15 ) to the parking plate frame  350 . To secure a plate, the handles, such as handle assembly  301 , must be unthreaded from the stud assemblies, such as stud assembly  310  as shown in  FIG. 11 . When both the upper T-handle assembly  300  and lower T-handle assembly  320  have been unthreaded, a parking plate may be positioned on the parking plate frame  350 . 
         [0067]      FIG. 15  is a perspective view of an MCDU landing frame/parking plate assembly  1500  having MCDU landing frame/base  150  and assembled thereon a parking positions plate  1502  removably attached by means of T-handle threaded shaft/stud assemblies  300  and  320 . In this exemplary embodiment parking positions plate  1502  is shown having seven connector assembly points  1504 . 
         [0068]    With reference now to  FIGS. 16 and 17 , perspective views of prior art MCDU landing base/frames  1600  (double tower) and  1700  (single tower) that may be modified with modular securing devices are provided. The modular securing devices including T-handle locking key  200  and ACME threaded shaft/stud assembly  300  may be added to either the of the MCDU landing frames  1600  or  1700 . As shown, fixed parking plates  1602  and  1702  are respectively fixably mounted onto frames  1650  and  1750 . With MCDUs  1610  and  1710  respectively inserted and installed within frames  1650  and  1750 , connector plugs may be received in connector receptacles  1612  and  1712  respectively. During replacement of MCDU  1610  or  1710 , the plugs connected to receptacles  1612  or  1712  may be de-mated and temporarily mated with parking connector terminals  1706  on frame  1750  (not shown on frame  1650 ). Parking connector terminals  1706  (not shown on frame  1650 ) are mounted onto parking plate  1702  by way of terminal mounts obscured behind terminals  1706  in  FIG. 17  but shown as terminal mounts  1604  in  FIG. 16 . Connector plugs and connector receptacles  1612 / 1712  form wet-mate connections. Connector plugs for a wet-mate seal when mated with parking terminals  1706 . The present invention may be adapted to work with other designs and configurations of frame assemblies in addition to the MCDU frame assemblies  1600  and  1700 , both of which are shown with MCDUs installed. 
         [0069]    With reference now to  FIGS. 18A and 18B , front and rear perspective views of an alternate embodiment of the present invention in an ROV operable configuration are provided. The modular MCDU securing device  1800  comprises the MCDU landing frame  1850 , MCDU  1810 , T-handle locking key  1820 , and T-handle locking key docking assembly  1822 . The T-handle locking key  1820  is installed in an unlocked position. The fixed bushing  1824  and T-handle locking key  1820  are similar to the T-handle locking key  200  and fixed bushing  220  shown in  FIG. 3 , however, the T-handle locking key  1820  extends inwardly from the front to the rear of the MCDU landing frame  1850 . This configuration provides for easier manipulation of the T-handle locking key  1820  by an ROV. When removed from the MCDU frame  1850 , the T-handle locking key  1820  may be placed in the docking assembly  1822  so that an ROV may easily manipulate the MCDU handle  1860  to remove the MCDU  1810 . After the MCDU  1810  is removed, or after a new MCDU is inserted, the T-handle locking key  1820  may be removed from the docking assembly  1822  and locked back into the MCDU landing assembly  1850  in the fixed bushing  1824 . 
         [0070]    While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concept described. Also, the present invention is not to be limited in scope by the specific embodiments described herein. It is fully contemplated that other various embodiments of and modifications to the present invention, in addition to those described herein, will become apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the following appended claims. Further, although the present invention has been described herein in the context of particular embodiments and implementations and applications and in particular environments, those of ordinary skill in the art will appreciate that its usefulness is not limited thereto and that the present invention can be beneficially applied in any number of ways and environments for any number of purposes. Accordingly, the claims set forth below should be construed in view of the full breadth and spirit of the present invention as disclosed herein.
The present invention relates generally to a modular locking and retaining mechanical design solution to reliably secure immersed, unrestrained and un-powered objects in a fluid environment to a fixed support surface such as a mounting frame or panel, with a quick connect/disconnect engagement method by a diver (i.e. Manual mate) or remote-operated vehicles (ROVs) mate, into a fixed mounting frame or panel installed at a subsea deployed platform for oil and gas offshore applications.