Technical Field

[0001 ] The present invention relates broadly to an evacuation coupling for connection to a fluid vessel for evacuation of fluid from the vessel.

Background of Invention

[0002] In hydrocarbon management systems for mining equipment there is a requirement to periodically change out oils, coolants and other fluids. This involves evacuation of spent or contaminated fluids from a tank associated with the equipment. This evacuation is generally effected by coupling an evacuation coupling to a mating coupling such as a receiver mounted to the tank. The evacuation coupling is connected to an evacuation hose which in turn is connected to an evacuation pump. The evacuation pump is activated once the evacuation coupling is connected to the receiver of the tank to provide a vacuum downstream of the tank which is effective in drawing the spent or contaminated fluids from the tank. These conventional evacuation systems have at least the following drawbacks:

i) the evacuation coupling can be unlatched from the tank during evacuation resulting in spillage with its associated environmental and WHS issues; ii) the evacuation coupling with the evacuation pump running can attract solids and particulate when not connected to the tank and this may prevent its further operation in for example latching to the receiver;

iii) the evacuation coupling may not be suited to connect to a range of different sized receivers and may for example require adaptors to cover the range of receivers.

Summary of Invention

[0003] According to the present invention there is provided an evacuation coupling for connection to a fluid vessel for evacuation of fluid from the vessel, said evacuation coupling comprising:

a coupling body including an elongate fluid passageway having a fluid inlet and a fluid outlet at its respective opposite ends adapted to couple to the fluid vessel and an evacuation source; an isolation valve mounted within the fluid passageway to control the flow of fluid through said passageway, the isolation valve including a valve head arranged for longitudinal movement within the fluid passageway for opening or closure of the isolation valve;

a valve actuator operatively coupled to the coupling body for longitudinal displacement relative to one another, the valve actuator coupled to the valve head to permit opening or closure of the isolation valve with the longitudinal displacement of the coupling body relative to the valve actuator which provides the longitudinal movement of the valve head for opening or closure of the isolation valve;

coupling means operatively coupled to the coupling body at the fluid inlet and adapted to releasably couple with the vessel, or a mating coupling associated with the vessel, for coupling of the evacuation coupling;

a coupling actuator mounted to the coupling body, the coupling actuator arranged to cooperate with:

i) the coupling means to permit its coupling to and uncoupling from the fluid vessel or the mating coupling;

ii) the valve actuator to restrict movement of the coupling actuator with the isolation valve opened and the coupling means coupled to the vessel, or the mating coupling, to prevent uncoupling of the evacuation coupling from the fluid vessel.

[0004] Preferably the valve actuator includes a valve actuator collar slidably mounted to the coupling body, said valve actuator collar being arranged with the isolation valve opened to abut with the coupling actuator to limit its movement to prevent uncoupling from the fluid vessel. More preferably the valve actuator collar is rotationally mounted about the coupling body whereby the longitudinal displacement between the coupling body and the valve actuator for opening or closure of the isolation valve is provided by relative rotational movement between the coupling body and the valve actuator collar. Even more preferably the coupling actuator is rotationally fixed to the coupling body whereby rotation of the coupling actuator provides rotation of the coupling body relative to the valve actuator collar for opening or closure of the isolation valve.

[0005] Preferably the valve head includes a poppet valve coupled to the valve actuator which is slidably mounted to the coupling body whereby rotation of the coupling body relative to the valve actuator provides the longitudinal movement of the valve head for opening or closure of the isolation valve. More preferably the valve actuator is arranged to engage the coupling body or vice versa where, on rotation of the coupling body relative to the valve actuator, the valve head is moved longitudinally for its opening or closure. Even more preferably the valve actuator includes an actuator key arranged to engage an annular keyway formed in the coupling body.

[0006] Preferably the evacuation coupling also comprises an inlet valve assembly mounted within the fluid passageway upstream of the isolation valve. More preferably the inlet valve assembly includes an inlet piston assembly arranged for axial displacement on coupling of the coupling body with the fluid vessel for opening of the inlet valve assembly.

[0007] Preferably the evacuation coupling is coupled to the fluid vessel via one of different sized receivers connected to the vessel. More preferably the inlet piston assembly includes an ancillary piston mounted within a primary piston slidably housed within the coupling body whereby either or both of said pistons are displaced by the receiver, depending on its size, on coupling of the coupling body with the fluid vessel.

[0008] Preferably the inlet valve assembly also includes an axially-oriented guide member to which the inlet piston assembly is slidably mounted. More preferably the guide member is elongate and connected at its opposite ends to the isolation valve and an inlet poppet valve, respectively, whereby opening of the isolation valve effects axial displacement of the inlet poppet valve via the guide member for increased opening of the inlet valve assembly. Even more preferably when the coupling body is uncoupled from the fluid vessel and the inlet valve assembly is closed, the inlet piston assembly is arranged to seat about the inlet poppet valve.

[0009] Preferably the valve actuator is coupled to the isolation valve via a coupling tail adapted to couple to an evacuation hose connected to the evacuation source. More preferably the coupling tail is fixed to the valve actuator and slidably mounted to the coupling body at the fluid outlet.

[0010] Preferably the evacuation coupling further comprises a check valve mounted within the fluid passageway at the fluid outlet and arranged to restrict reverse flow of fluid through the fluid passageway. More preferably the check valve is mounted within the coupling tail and urged closed via check valve biasing means.

Brief Description of Drawings

[001 1 ] In order to achieve a better understanding of the nature of the present invention a preferred embodiment of an evacuation coupling for connection to a fluid vessel for evacuation of fluid from the vessel will now be described, by way of example only, with reference to the accompanying drawings in which:

Figures 1 to 4 show various views of an evacuation coupling according to a preferred embodiment of the invention;

Figure 5 is a perspective view shown in part cutaway of the evacuation coupling of figures 1 to 4 connected to an exemplary receiver connected to a vessel;

Figures 6 to 8 show the evacuation coupling of figure 5 in various sectional and detail views;

Figure 9 is a perspective view shown in part cutaway of the evacuation coupling of figure 5 with its isolation valve opened;

Figures 10 to 1 2 show the evacuation coupling of figure 9 in various sectional and detail views;

Figure 13 is a perspective view shown in part cutaway of the evacuation coupling of the preceding embodiments connected to another receiver and with the isolation valve opened;

Figures 14 to 1 6 shows the isolation valve of figure 13 in various sectional and detail views;

Figure 17 illustrates the evacuation coupling of the preceding embodiment shown in perspective and part cutaway;

Figures 18 to 20 show the evacuation coupling of figure 17 in various sectional and detail views; Figure 21 shows the evacuation coupling of the preceding embodiment in perspective with part of the valve actuator shown in phantom and the coupling means partly cutaway;

Figures 22 to 25 show perspective, elevation and sectional views of the coupling body of the evacuation coupling of the preceding embodiment;

Figures 26 to 29 show perspective, elevation and sectional views of an ancillary piston of the inlet piston assembly of the evacuation coupling of the preceding embodiment;

Figures 30 to 34 show perspective, elevation and sectional views of a coupling tail of the evacuation coupling of the preceding embodiment.

Detailed Description

[0012] As shown in figures 1 to 4 there is an evacuation coupling 10 according to a preferred embodiment of the invention. The evacuation coupling 10 is designed for connection to a fluid vessel (not shown) for evacuation of fluid from the vessel.

[0013] Figures 5 to 12 illustrate connection of the evacuation coupling 10 to a relatively small diameter receiver 12 whereas figures 13 to 16 show connection of the same evacuation coupling 10 to a relatively large diameter receiver 12'. The evacuation couplings 1 , 3, 5, 9, 10 and 13 of figures 2 to 7 are the same and have thus been shown with their components referenced with the same reference numerals.

[0014] The evacuation coupling 10 comprises a coupling body 14 including an elongate fluid passageway 18 having a fluid inlet 20 and a fluid outlet 22 at its respective opposite ends. The evacuation coupling 10 also comprises an isolation valve 24 mounted within the fluid passageway 18 and including a valve head in the form of a poppet valve 25 designed to control the flow of fluid. The evacuation coupling 10 further comprises a valve actuator 26 operatively coupled to the isolation valve 24 to effect its opening and closure. The evacuation coupling 10 additionally comprises coupling means which is in this embodiment in the form of ball locking mechanism designated at 28 and designed to releasably couple with the vessel via the receiver such as 12. Importantly, the evacuation coupling 10 also comprises a coupling actuator 30 mounted to the coupling body 14 and arranged to cooperate with:

1 . the ball lock mechanism 28 to permit its coupling to and uncoupling from the fluid vessel;

2. the valve actuator 26 to restrict movement of the coupling actuator 30 with the isolation valve 24 opened and the ball locking mechanism 28 of this

embodiment coupled to the vessel to prevent uncoupling of the evacuation coupling 10 from the vessel.

[0015] In this embodiment the valve actuator 26 includes a valve actuator collar 32 rotationally mounted to the coupling body 14 whereby opening of the isolation valve 24 is effected by relative rotational movement between the coupling body 14 and the valve actuator collar 32. This relative rotational movement translates into longitudinal displacement of the coupling body 14 relative to the valve actuator collar 32. This longitudinal displacement drives longitudinal movement of the valve head 25 of the isolation valve 24 for its opening and closure. As best shown in figures 9 and 10 the valve actuator collar 32 is arranged with the isolation valve 24 opened to abut with the coupling actuator 30 to limit its movement to prevent uncoupling from the fluid vessel. The coupling actuator 30 is in this example keyed to the coupling body 14 whereby rotation of the coupling actuator 30 provides rotation of the coupling body 14 relative to the valve actuator collar 32 for opening and closure of the isolation valve 24. Alternatively the valve actuator collar 32 is rotated relative to the coupling body 14 to provide the longitudinal displacement for opening and closure of the isolation valve 24.

[0016] In this embodiment the coupling actuator 30 is keyed or otherwise rotationally fixed to the coupling body 14 via a pin, dowel, grub screw 34 or equivalent. The grub screw 34 is in this example one of three grub screws fixed to an annular wall 36 of the coupling actuator 30 and each grub screw such as 34 slidably engages a longitudinally oriented slot or keyway 38 in the coupling body 14. This grub screw 34 and keyway 38 arrangement is thus repeated three times around the perimeter of the coupling actuator 30. The coupling actuator 30 is thus designed to move axially to cooperate with the coupling means or ball lock mechanism 28 for coupling to or uncoupling from the receiver 12. The coupling actuator 30 in this embodiment will also function to provide for rotation of the coupling body 14 because they are rotationally keyed to one another.

[0017] The coupling actuator 30 includes an actuator spring 40 arranged to urge the coupling actuator 30 into an extended position for retention of the ball lock mechanism 28 which is thus coupled or latched to the receiver 12. The coupling means or ball lock mechanism 28 is uncoupled or unlatched from the receiver 12 by retraction of the coupling actuator 30 to permit release of the ball lock mechanism 28 into a rebate 42 formed in an inside face of the annular wall 36. As best shown in figures 5 and 6 with the isolation valve 24 closed the evacuation coupling 10 can be coupled or uncoupled from the receiver 12 by retraction and release of the coupling actuator 30. On the other hand, the evacuation coupling 10 shown in figures 9 and 10 with the isolation valve opened cannot be uncoupled from (or coupled to) the receiver 12 by axial retraction of the coupling actuator 30. This is because the coupling actuator 30 abuts the valve actuator collar 32 preventing its displacement from the extended position of the coupling actuator 30.

[0018] The isolation valve 24 of this embodiment includes the valve head in the form of a poppet valve 25 located within a poppet valve seat 46 secured within the coupling body 14. The poppet valve 25 is arranged for longitudinal or axial movement within the poppet valve seat 46 for opening and closure of the isolation valve 24. This axial movement of the poppet valve 25 is provided by the relative longitudinal displacement between the coupling body 14 and the valve actuator collar 32. The poppet valve 25 is fixed to the valve actuator collar 32 whereby rotation of the coupling body 14 effects axial or longitudinal movement of the poppet valve 25 relative to the valve poppet seat 46 for its opening and closure.

[0019] The valve actuator 26 of this embodiment engages the coupling body 14 via an actuator key 48 where on rotation of the coupling body 14 relative to the valve actuator 26 there is provided the required relative longitudinal displacement. In this example the actuator key 48 is in the form of an actuator pin, dowel, grub screw or equivalent arranged to engage an annular keyway 50 formed in the coupling body 14. In this embodiment the actuator key 48 and keyway 50 arrangement is repeated three times around the circumference of the coupling body 14. This is best shown in figures 21 , 22 and 25 where it can be seen that the annular keyway 50 is in the form of generally Z-shaped channel having a ramped portion 52 which provides for longitudinal displacement of the coupling body 14 relative to the valve actuator collar 32 for opening and closure of the isolation valve 24. The ramped portion 52 is located intermediate and formed continuous with parallel end portions 54a and 54b formed at each end of the Z-shaped keyway or channel 50. The diameter of the actuator key such as the grub screws 48 may be increased together with the mating dimensions of the keyway 50 to increase the contact area between the contacting surfaces.

[0020] In a variation on this actuator key 48 and annular keyway 50 design, the evacuation coupling 10 may instead include an array of ball bearings located within a bearing race defined by the annular keyway 50 formed in the coupling body 14 and a corresponding channel formed in the actuator collar 32. The ball bearings replace the key in the form of the grub screws 48 and create a rolling-type movement between the ball bearings and the associated bearing race (not shown). In this variation the two (2) annular keyways such as 50 may be replaced with a single bearing race.

[0021 ] The evacuation coupling 10 of this embodiment includes a coupling tail 56 adapted to couple to an evacuation hose (not shown) connected to an evacuation source such as an evacuation pump (now shown). The coupling tail 56 may be coupled to the evacuation hose via a swivel fitting in the form of a unitary assembly (not shown). The swivel fitting allows for ease of rotation of the valve actuator collar 32 relative to the coupling body 14 should opening and closure of the isolation valve 24 be effected in this way. In some installations the evacuation or discharge (suction) hose places a cantilevered load onto the evacuation coupling 10 and the receiver 12 to which it is attached. This cantilevered load (unless mitigated by manually supporting the weight) increases the manual effort required to contra-rotate the collar 32 relative to the coupling body 14. The optional swivel fitting is expected to assist in rotation of the collar 32 relative to the body 14

[0022] The coupling tail 56 is fixed to the valve actuator 26 and slidably mounted within the coupling body 14 at or proximal the fluid outlet 22 of the fluid passageway 18. The poppet valve 25 is fixed or otherwise secured to the coupling tail 56 so that relative longitudinal displacement between the coupling body 14 and the valve actuator 26 provides longitudinal or axial movement of the poppet valve 25 for its opening and closure. This relative longitudinal displacement is provided in this example by rotation of the coupling actuator 30 relative to the valve actuator 26. In an alternative arrangement it may be provided by reciprocating movement of the coupling body 14 relative to the valve actuator 26 with for example a ratchet mechanism between the coupling body 14 and the valve actuator 26.

[0023] The evacuation coupling 10 of figures 5 to 8 is shown with the isolation valve 24 closed whereas figures 9 to 16 depict the evacuation coupling 10 of the isolation valve 24 opened. As viewed from the coupling tail 56 or evacuation hose (not shown) the coupling actuator 30 is rotated anti-clockwise relative to the valve actuator 26 for axial displacement of the coupling body 14 and opening of the poppet valve 25. The actuator key 48 is arranged relative to the keyway 50 whereby rotation of the coupling actuator 30 commencing from closure of the isolation valve 24 progresses through the following stages:

1 . Initial rotation moves the key 48 through one of the parallel sections 54a of the Z-shaped channel 50 without axial displacement of the coupling body 14;

2. Continued rotation moves the key 48 through the ramped section 52 for

gradual axial displacement of the coupling body 14 and progressive opening of the poppet valve 25;

3. Further rotation moves the key 48 through the other parallel section 54b of the Z-shaped channel 50 without further axial displacement of the coupling body 14.

[0024] It will be appreciated that the annular keyway 50 may be reconfigured to vary the rate at which the isolation valve 24 is opened. The annular keyway 50 may also be reshaped so that opening of the isolation valve 24 is provided by clockwise rather than anti-clockwise rotation of the coupling actuator 30. The annular keyway 50 may in an alternative embodiment be located in the valve actuator 26 with the actuator key secured to the coupling body 14.

[0025] The evacuation coupling 10 also comprises an inlet valve assembly designated generally at 60 in figure 9 is mounted within the fluid passageway 18 at or proximal the fluid inlet 20 upstream of the isolation valve 24. In this example the inlet valve assembly 60 includes an axially-oriented guide member 62 connected at its opposite ends to the isolation valve 24 and an inlet poppet valve 64 respectively. The inlet valve assembly 60 includes an inlet piston assembly 66 arranged for axial displacement on coupling of the coupling body 14 with the receiver 12 for opening of the inlet valve assembly 60. The inlet piston assembly 66 is also arranged to seat about the inlet poppet valve 64. This means that opening of the isolation valve 24 provides axial displacement of both the poppet valve 25 at or proximal the fluid outlet 22 together with the inlet poppet valve 64 via the guide member 62. This axial displacement of the inlet poppet valve 64 provides for increased opening of the inlet valve assembly 60 downstream of the fluid inlet 20 and through the fluid passageway 18. This can be best seen in figures 7, 1 1 and 15. On the other hand, figures 17 and 18 show the evacuation coupling 10 uncoupled from the receiver 12 with the inlet valve assembly 60 fully closed. In this fully closed position the:

1 . poppet valve 25 of the isolation valve 24 is retracted into seated engagement with the poppet valve seat 46;

2. inlet piston assembly 66 is released by the receiver 12 and the influence of a piston spring 68 urges it toward the fluid inlet 20;

3. inlet poppet valve 64 provides seated closure for the inlet piston assembly 66 for closure of the fluid passageway 18.

[0026] In this embodiment the inlet piston assembly 66 includes an ancillary piston 70 mounted within a primary piston 72. The primary piston 72 is slidably housed within the coupling body 14 whereby either the primary piston 72 alone or both of the pistons 70 and 72 can be displaced by the receiver 12, depending on its size, on coupling of the coupling body 14 with the receiver 12. This can best be seen in:

1 . figures 5 to 1 1 where the relatively small diameter receiver 12 abuts both the ancillary and primary pistons 70 and 72 for opening of the inlet valve assembly 60;

2. figures 13 and 15 where the relatively large diameter receiver 12' abuts and displaces the primary piston 72 only for opening of the inlet valve assembly 60.

[0027] It will be appreciated that this design of the inlet piston assembly 66 allows the one evacuation coupling 10 to couple to a range of receivers of different sizes.

[0028] The evacuation coupling 10 of this embodiment further comprises a check valve 76 mounted within the fluid passageway 18 at the fluid outlet 22 downstream of the isolation valve 24. The check valve 76 is mounted within the coupling tail 56 and urged closed via check valve biasing means in the form of check valve spring 78 to restrict reverse flow of fluid through the fluid passageway 18. The check valve 76 of this embodiment includes a valve head 80 formed integral with a valve stem 82. The valve stem 82 is slidably mounted coaxial with a valve stem mount 84 secured within the coupling tail 56.

[0029] As shown in figure 32 the coupling tail 56 includes a ported end wall 88 having a series of circular openings such as 90a which are arranged to be sealed closed by the check valve 76 under the biasing force of the check valve spring 78. The ported end wall 88 also provides axial mounting for the poppet valve 25. The poppet valve 25 is thus driven axially open and closed via the coupling tail 54 in the valve actuator collar 32 which are secured to one another. As described in greater detail in the preceding paragraphs this axial movement is effected by relative rotation between the valve actuator 26 and in particular the valve actuator collar 32 and the coupling body 14 for relative longitudinal displacement between these components. This relative displacement is typically effected by rotation of the coupling actuator 30 which drives the coupling body 14 for rotation inside the actuator collar 32.

[0030] Figures 13 and 15 are essentially identical to the preceding figures except the same evacuation coupling 10 is coupled to the relatively large diameter receiver 12'. These figures depict the evacuation coupling 10 with the isolation valve 24 in its opened position. The larger receiver 12' abuts the primary piston 72 only for its displacement in a downstream direction for opening of the fluid passageway 1 8 via the inlet valve assembly 60. The ancillary piston 70 is in effect redundant and in conjunction with the inlet poppet valve 64 abuts the flush face of the receiver 12' for opening of its associated receiver poppet 90'. The receivers 12 and 12' are otherwise of a conventional construction.

[0031 ] The fluid passageway 18 can be best seen in the sectional and part cutaway views of figures 9 and 10 for the small diameter receiver 12, and figures 13 and 14 for the large diameter receiver 12'. The flow of fluid through the passageway 18 has been schematically shown with arrowed flow lines 94. The flow lines 94 are essentially the same except for the:

1 . smaller receiver of figures 9 and 10 the fluid passes through an upstream

cupped-end 96 of the ancillary piston 70 via a series of openings such as 98a in its wall as best seen in figure 1 1 ; 2. relatively large receiver 12' of figures 13 and 14 the fluid flows through an annular space 99 formed between the displaced primary piston 72 and the ancillary piston 70 which is not displaced by the receiver 12' as best seen in figure 14.

[0032] Figures 26 to 29 illustrates the ancillary piston 70 with its cup-shaped end 96 and circumferential opening such as 98a. The ancillary piston 70 slidably mounts coaxial with the guide member 62 about which ancillary piston biasing means in the form of compression spring 100 is mounted. The ancillary piston spring 100 urges the ancillary piston 70 into seated engagement with the inlet poppet valve 64 as best seen in figures 17 to 19.

[0033] Figure 21 intends to better illustrate interaction between the relative components to effect both coupling of the evacuation coupling 10 with a receiver such as 12, and opening or closure of the isolation valve 24 by rotation of the coupling body 14 relative to the valve actuator 26. The coupling actuator 30 of this

embodiment reciprocates axially by slidable engagement of the grub screw 34 with the corresponding keyway 38 in the coupling body 14. The coupling actuator 30 is retracted against the biasing force of the spring 40 to permit release of the ball lock arrangement 28 from the receiver such as 12. The coupling actuator 30 is otherwise rotationally fixed to the coupling body 14 whereby rotation of the coupling actuator 30 provides rotation of the coupling body 14 relative to the valve actuator 26. This relative rotation rotates the annular keyway or channel such as 50 about the corresponding actuator key such as the grub screw 48. In this example and as described in the preceding paragraphs, the cooperating actuator key 48 and annular keyway 50 are repeated in the form of three Z-shaped channels 50 formed about the perimeter of the coupling body 14. The three channels such 50 are arranged relative to their respective actuator keys such as 48 so that axial displacement of the isolation valve 24 is synchronised by the actuator key 48 entering and exiting the ramped intermediate portion 52 at substantially the same time.

[0034] The general steps involved in operation of the evacuation coupling 10 of this embodiment are as follows: 1 . The evacuation coupling is coupled or latched to the relevant receiver such as 12 or 12' by retracting the coupling actuator 30 and locating the ball lock arrangement 28 about the receiver 12;

2. The actuator coupling 30 is released to retain the ball lock arrangement 28 on the receiver 12;

3. The isolation valve 24 is opened by rotation of the actuator coupling 30 and the associated coupling body 14 relative to the valve actuator 26.

[0035] Importantly, the coupling means or ball lock mechanism 28 cannot be uncoupled from the receiver such as 12 with the isolation valve 24 opened. This can best be seen in figures 9, 10, 13 and 14 where the coupling actuator 30 is prevented from axial displacement for release of the ball lock mechanism 28 by its abutment with the valve actuator collar 32. The vessel with which the receiver is associated is evacuated using an appropriate evacuation pump or other source. The evacuation pump is shut down and the isolation valve 24 closed to permit uncoupling of the evacuation coupling 10 from the receiver 12. This can best be seen in figures 5 and 6 where the separation between the actuator coupling 30 and the valve actuator collar 32 permits retraction of the actuator coupling 30 for release of the ball lock

mechanism 28 from the receiver 12.

[0036] Now that a preferred embodiment of the present invention has been described it will be apparent to those skilled in the art that the evacuation coupling has at least the following advantages:

1 . Its design only permits uncoupling from the vessel when the isolation valve is closed minimising the likelihood of spillage;

2. The evacuation coupling is designed to suit at least two different sized

receivers largely negating the need for adaptors to cover a range of receivers;

3. The evacuation coupling in its preferred form incorporates an isolation valve which can be actuated by manipulation of the actuator coupling without necessarily requiring tooling;

4. The evacuation coupling in its preferred form incorporates a check valve which minimises spillage from the evacuation hose when the coupling is detached from the fluid vessel. [0037] Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. For example, the isolation valve may be opened by a valve actuator which has a different action to the preferred embodiment provided it also functions as broadly defined in the specification. The evacuation coupling may in a simpler form couple to a vessel without a receiver and as such not require the inlet valve assembly described. The check valve is also optional where the evacuation coupling may rely upon the isolation valve to prevent reverse fluid flow. All such variations and modifications are to be considered within the scope of the present invention the nature of which is to be determined from the foregoing description.