SCREEN ASSEMBLIES FOR A VIBRATORY SEPARATOR

Abstract: A screen assembly for a vibratory separator, the screen assembly comprising at least one wire mesh screen (130; 260; 330) formed with undulating mesh material having a series of ridges spaced apart by a series of valleys, and a first series of spaced apart rods (136; 266; 336), the arrangement being such that, in use, the wire mesh screen is supported by the first series of spaced apart rods.

Description: Screen Assemblies for a Vibratory Separator The present invention relates to screen assemblies for a vibratory separator and, more particularly but not exclusively, to screen assemblies for use in shale shakers . The present invention also relates to a releasable locking device for securing a screen assembly to a vibratory separator. W en drilling a wellbore in the earth' s surface, drilling fluid is used to maintain the tip of a drill cool and to carry solids to the surface of the wellbore. Once at the surface the solids are removed from the drilling fluid which can then be re-used. Types of apparatus that can remove solids from drilling fluid include a vibratory separator known as shale shaker. Typically, it is known to provide such equipment with one or more screens of wire mesh for filtering the drilling fluid. Typically, the wire mesh is very fine and does not have a high durability. The problem of providing the necessary durability to known screens has been addressed, in one manner, by bonding the wire mesh to a perforated plastic plate . An example of this is described in 094/15723. However, although perforated plates increase the durability of such screens , they have a "blinding" effect on the screen in which throughput of the drilling fluid is reduced. In addition, it is known to mount a screen in a frame prior to use in order to make for faster fitting and removal to a shale shaker. However, since such screens are typically constructed off-site, use of frames makes the screens rigid and awkward to transport and handle, and requires larger storage space. The frame itself also contributes to the blinding effect. In contrast screening material can o ten be transported in rolls . The present invention seeks to address at least one or more disadvantages of the prior art. According to one aspect of the present invention there is provided a screen assembly for a vibratory separator, the screen assembly comprising at least one wire mesh screen formed with undulating mesh material having a series of ridges spaced apart by a series of valleys , and a first series of spaced apart rods, the arrangement being such that, in use, the wire mesh screen is supported by the first series of spaced apart rods . Such an arrangement addresses the problem of providing the necessary support to the screen whilst at the same time inhibiting the effects of "blinding" . Advantageously, said first series of spaced apart rods extend in a direction which is transverse to the ridges and valleys of said at least one wire mesh screen. Preferably, said screen assembly further comprises a second series of spaced apart rods arranged, in use, to support said first series of spaced apart rods. Advantageously, said second series of spaced apart rods extend transverse to said first series of spaced apart rods . Preferably, said first series of spaced apart rods are corrugated. Advantageously, said first series of spaced apart rods have a corrugated surface Preferably, the at least one wire mesh screen comprises a plurality of two or more wire mesh screens . Advantageously, the plurality of wire mesh screens are adhered together. Preferably, the at least one wire mesh screen includes at least one upper wire mesh screen having a first mesh size and a lower wire mesh screen having a mesh size coarser than the first screen mesh size. Advantageously, said screen comprises a pair of spaced apart top bars , one top bar on each side of the screen assembly at an outer edge thereof. Preferably, the undulating shape of the at least one wire mesh screen forms a series of end openings on two sides thereof, and said screen assembly further comprises plug apparatus for, in use, plugging said series of end openings . Advantageously said series of end openings are encapsulated in encapsulating material . Preferably, said screen assembly further comprises a perforated corrugated plate which supports said at least one wire mesh screen. Advantageously, the at least one wire mesh screen is adhered to the corrugated perforated plate. Preferably, said screen assembly further comprises an adapter bar on which the at least one wire mesh screen is mounted, the adapter bar having recesses for receiving the first series of spaced-apart rods . Advantageously, said screen assembly further comprises a layer of seal material on top of the adapter bar . According to another aspect of the present invention there is provided a screen assembly for a vibratory separator, the screen assembly comprising at least one wire mesh screen formed with undulating mesh material having a series of ridges spaced apart by a series of valleys , and a layer of wire mesh material , the arrangement being such that, in use, the at least one wire mesh screen is supported by the layer of wire mesh material . Such an arrangement addre sses the problem of providing the necessary support to the screen whilst at the same time inhibiting the effects of "blinding" . Preferably, said layer of wire mesh material has a coarser mesh than said at least one wire mesh screen. Advantageously, said screen assembly further comprises a perforated corrugated plate which supports said at least one wire mesh screen. Preferably, the at least one wire mesh screen is adhered to the corrugated perforated plate. Advantageously, the at least one wire mesh scr een comprises a plurality of two or more wire mesh screens . Preferably, the plurality of wire mesh screens are adhered together. Advantageously, the at least one wire mesh screen includes at least one upper wire mesh screen having a first mesh size and a lower wire mesh screen having a mesh size coarser than the first screen mesh size. Preferably, said screen assembly further comprises a pair of spaced apart top bars, one top bar on each side of the screen assembly at an outer edge thereof. Advantageously, the undulating shape of the at least one wire mesh screen forms a series of end openings on two sides thereof, and further comprising plug apparatus for, in use, plugging said series of end openings . Preferably, said series of end openings are encapsulated in encapsulating material . Advantageously, the at least one wire mesh screen has opposed spaced-apart front and rear edges encapsulated in encapsulating material . Preferably there is provided a vibratory separator fitted with a screen in accordance with the present invention, wherein said screen assembly is not mounted in a frame . According to another aspect of the present invention there is provided a frameless screen assembly for a vibratory separator, the frameless screen assembly comprising at least one wire mesh screen formed with undulating mesh material having a series of ridges spaced apart by a series of valleys , and a first series of spaced apart rods, the arrangement being such that, in use, the wire mesh screen is supported by the first series of spaced apart rods . According to another aspect of the present invention there is provided a frameless screen assembly for a vibratory separator, the frameless screen assembly comprising at least one wire mesh screen formed with un dulating mesh material having a series of ridges spaced apart by a series of valleys , and a layer of wire mesh material, the arrangement being such that, in use, the at least one wire mesh screen is supported by the layer of wire mesh material . A screen assembly in accordance with the present invention, in preferred embodiments, does not require a wire mesh screen to be mounted in or on a frame before being fitted to a shale shaker. Further, said screen assemblies do not require the support of planar perforated plates and can be mounted directly on the wear strip of certain shale shakers . In alternative preferred embodiments the wire mesh screen can be mounted directly on a certain shale shakers with standard clamp/hookstrip arrangements . According to another aspect of the present invention there is provided a releasable locking device for securing a screen assembly to a vibratory separator, which releasable locking device comprises an arm movable between a first position and a second position, a plunger pivotally connected to said arm for, in use, retaining said screen assembly to said vibratory separator in said first position and releasing said screen assembly from said vibratory separator in said second position, and first spring means for, in use, inhibiting movement of said arm from said first and second positions. Advantageously, said releasable locking device further comprises second spring means for, in use, inhibiting movement of said arm from said first position. For a better understanding of the present invention reference will now be made, by way of example, to the accompanying drawings in which : - Fig. 1A is a top plan view, partially cut away, of a first embodiment of a screen according to the present invention; Fig. IB is an exploded view of one end of the screen of Fig. 1A; Fig. 1C is a view of one end of the screen of Fig. 1A; Fig. ID is an exploded view of one side of the screen of Fig. 1A; Fig. 2A is a top plan view, partially cut away, of a second embodiment of a screen according to the present invention; Fig. 2B is an exploded view of one end of the screen of Fig. 2A; Fig. 2C is a view of one end of the screen of Fig. 2A. Fig. 2D is an exploded view of one side of the screen of Fig. 2A; Fig. 3A is a top plan view, partially cut away, of a third embodiment of a screen according to the present invention; Fig. 3B is an exploded view of one end of the screen of Fig. 3A; Fig. 3C is a view of one end of the screen of Fig. 3A; Fig . 3D is an exploded view of one side of the screen of Fig. 3A; Fig. 3E is an exploded view of one side of the screen of Fig. 3A and an adapter bar for mounting the screen on a vibratory separator apparatus ; Fig. 3F is a view of part of one end of a screen in accordance with the present invention on a mounting structure of a vibratory shaker apparatus; Fig . 3G is a view of one end of an adapter bar of the apparatus of Fig. 3E; Fig. 4A is a top plan view, partially cut away, of a fourth embodiment of a screen in accordance with the present invention; Fig. 4B is an exploded view of one end of the screen of Fig. 4A; Fig. 4C is a view of one end of the screen of Fig. 4A; Fig. 5A is a top plan view, partially cut away, of a fifth embodiment of a screen in accordance with the present invention; Fig. 5B is an exploded view of one end of the screen of Fig. 5A; Fig. 5C is a view of one end of the screen of Fig. 5A; Fig. 5D is an exploded view of one side of the screen of Fig. 5A; Fig. 6 is a view of one side of a screen locking apparatus in use with a screen in accordance with the present invention; Fig. 7A is a side view of a first embodiment of a releasable screen locking apparatus in accordance with the present invention; Fig. 7B shows the apparatus of Fig. 7A in an unlocked position; Fig. 7C is a top plan view of the apparatus of Fig. 7B; and Fig. 8 is a side view of a second embodiment of a releasable screen locking apparatus in accordance with the present inventio . Referring to Figs . 1A - ID there is shown a screen 130 which comprises wire mesh layers 131, 132, 133 (any or any two of which are optional) mounted over rods 136. Optionally, the wire mesh layers 131, 132, 133 may be adhered (adhesively, by sintering, and/or bonding) together. The rods 136 may be made of metal (e.g. steel, stainless steel, zinc, zinc alloys, aluminium, aluminium alloys, copper, copper alloys) plastic, composite or fiberglass. The rods 136 are substantially circular in cross-section, although it is envisaged that any suitable shape cross-section may be employed. Top bars 135 extend along two sides of the screen 130. Open ends of the screen 130 on two sides thereof are plugged with plugs 137 which are made of any suitable metal, plastic (e.g. urethane) , wood, fiberglass, or composite material and are held in place by a friction fit and/or suitable adhesive including but not limited to epoxy or glue (e.g. but not limited to commercially available 3M Jet Melt or 3M TS230) . Also, preferably, front and rear edges 142, 143 of the screen 130 are encapsulated by the adhesive or glue (e.g. but not limited to urethane) . An adapter bar 140 has recesses 141 for receiving the rods 136 and a plurality of bolt holes 148 for attaching the adapter bar 140 to a typical part or wear or seal strip of known shakers. Optionally, the rods 136 may be adhered to the recesses 141. Alternatively, bolts (not shown) may extend through a shaker basket and into the side of the adapter bar 140. Seal material (e.g. rubber, plastic BUNA-N, etc.) 144 may be used on top of the adapter bar 140. In one aspect the wire mesh layers 131 and 132 are either 1, 2, or 3 mesh and the layer 133 is of a coarser mesh, e.g. 12 X 12 down to 8 X 8 (or between 8 X 12 and 12 X 8) . It is also within the scope of this invention for the layers 131, 132, 133 to be any mesh size. In one aspect a screen 130 is made by bonding the layers 131 and 132 into a sheet with epoxy across substantially the entire surfaces of the layers ; then the resulting sheet is corrugated and the layer 133 is bonded to the sheet. In use, the adapter bar 140 is bolted or otherwise fixed to a shaker. The wire mesh layers 131, 132, 133 and the rods 136 are then clamped between the top bar 135 and the adapter bar 140. The rods 136 inhibit flexing of the screen during use and increase the longevity of the screen, whilst at the same time reducing the effects of "blinding" . This arrangement also obviates the need for a frame and/or planar perforated plate to support the screen. It also obviates the need for fused plastic to bond the wire mesh layers together. It is also within the scope of this embodiment for there to be a second series of rods which extend transverse to the rods 136 to provide extra support therefor . Referring to Figs . 2A - 2D there is shown a screen 260 which comprises wire mesh layers 261, 262, 263 (any or any two of which may be omitted) , corrugated rods 266, rods 265 underlying parts of the corrugated rods 266, and encapsulation material 269 (similar to that of the screen 130) which encapsulates front and rear edges of the wire mesh layers 261, 262, 263 and corrugated rods 266. Alternatively, some of the internal bars may be included in the encapsulation material. Top bars 267 are like the top bars 135 of the screen 130. An adapter bar 268 is like the bar 140 with side bolt holes 264 for bolting the adapter bar 268 and the screen 260 attached thereto to a shaker basket. The adapter bar 268 has rod recesses 264' and a top seal layer 268' (like the material 144 of screen 130) . The screen 260 can be assembled on a shaker in a similar manner to the screen 130. The screen 230 includes the same benefits as the screen 130. Further, the corrugated rods 266 increase the contact area with the screen 260. Therefore the weight of the screen 260 is not concentrated at the valleys thereof, which helps to reduce any local wearing effect that the rods may have on the screen 260. Further, this is achieved without "blinding" the screen anymore than the rods 136 blind the screen 130. The rods 265 provide extra rigidity to the corrugated rods 266, although they are not essential for this embodiment of the invention. The rods 265 could be spot welded to the corrugated rods 266. Referring to Figs . 3A - 3E there is shown a screen 330 which comprises wire mesh layers 331, 332, 333 (any or any two of which are optional) on a perforated corrugated plate 334 which is mounted over rods 336. Optionally, the wire mesh layers 331, 332, 333 may be adhered (adhesively, by sintering, and/or bonding) to the perforated corrugated plate 334. The rods 336 may be made of metal (e.g. steel, stainless steel, zinc, zinc alloys, aluminium, aluminium alloys, copper, copper alloys) plastic, composite or fiberglass. The rods 336 are substantially circular in cross-section, although it is envisaged that any suitable shape cross-section may be employed. Top bars 335 extend along two sides of the screen 330. Open ends of the screen 330 on two sides thereof are plugged with plugs 337 which are made of any suitable metal, plastic (e.g. urethane), wood, fiberglass, or composite material and are held in place by a friction fit and/or suitable adhesive including but not limited to epoxy or glue (e.g. but not limited to commercially available 3M Jet Melt(TM) or 3M TS230) . Also, preferably, front and rear edges 342, 343 of the screen 330 and the perforated corrugated plate 334 are encapsulated by the adhesive or glue (e.g. but not limited to urethane) . An adapter bar 340 has recesses 341 for receiving the rods 336 and a plurality of bolt holes 348 for attaching the adapter bar 340 to a typical part or wear or seal strip of known shakers. Optionally, the rods 336 may be adhered to the recesses 341. Alternatively, bolts (not shown) may extend through a shaker basket and into the side of the adapter bar 340. Seal material (e.g. rubber, plastic BUNA-N, etc.) 344 may be used on top of the adapter bar 340. In one aspect the wire mesh layers 331 and 332 are either 1, 2, or 3 mesh and the layer 333 is of a coarser mesh, e.g. 12 X 12 down to 8 X 8 (or between 8 X 12 and 12 X 8) . It is also within the scope of this invention for the layers 331, 332, 333 to be any mesh size. The perforated corrugated plate 334 is, in certain aspects, made of metal, e.g. but not limited to 20 gauge carbon steel . In one aspect the screen 330 is made by bonding the layers 331 and 332 into a sheet with epoxy across substantially the entire surfaces of the layers; then the resulting sheet is corrugated and the layer 333 is bonded to the sheet. The screen 330 can be assembled on a shaker in a similar manner to the screens 130 and 230. The perforated corrugated plate 334 provides extra support to the screen . Referring to Fig. 3F the screen 330 is shown clamped to a shaker basket 346 between a top bar 335 and a ledge 347 of a shaker basket 346. Clamping is facilitated by means of a locking bar 338 (hereinafter described) . Referring to Figs . 4A - 4C there is shown a screen 450 which comprises wire mesh layers 451, 452, 453 (any or any two of which may be omitted) and a wire mesh lower layer 459 which may be any desired mesh size but which is, in certain embodiments a coarser mesh than any of the meshes 451, 452, 553. Fig. 4A omits the wire mesh layers 451, 452, 453 for clarity. In one particular aspect the wire mesh layer 459 is between 1 X 1 and 4 X 4 mesh (including between 1 X 4 and 4 X 1 mesh) . In particular embodiments the lower layer of wire mesh 459 is 12 X 12, 8 X 8 or 4 X 4 mesh, and may include meshes between 8 X 12 to 12 X 8. The layers may have upturned ends 458 so that the screen 450 may be used with any standard clamp/hookstrip arrangement . The wire mesh layers 451 , 452, 453 may be bonded together as a unit. The upturned ends 458 may be formed before or after bonding. Preferably the front and rear edges of the screen 450 are encapsulated by adhesive or glue and plugs 457 plug screen ends. The wire mesh lower layer 459 inhibits flexing of the screen 450 during use and increases longevity of the screen 550 , whilst at the same time reducing the effects of "blinding" . This arrangement also obviates the need for a frame and/or planar perforated plate to support the screen. It also inhibits the need for fused plastic to bond the wire mesh layers together .. As with any screen herein, multiple wire meshes may be bonded and/or secured together prior to corrugating. Referring to Figs . 5A - 5D there is shown a screen 550 which comprises wire mesh layers 551 , 552 , 553 (any or any two of which may be deleted) , a perforated corrugated plate 554, and a lower layer of wire mesh 559 which may be any desired mesh size but which is, in certain embodiments a coarser mesh than any of the meshes 551 , 552 , 553. In one particular aspect the lower layer of wire mesh 559 is between 1 X 1 and 4 X 4 mesh (including between 1 X 4 and 4 X 1 mesh) . In particular embodiments the lower layer of wire mesh 559 is 12 X 12, 8 X 8 or 4 X 4 mesh, and may include meshes between 8 X 12 to 12 X 8. The wire mesh layers 551 , 552 , 553 may have upturned ends 558 so that the screen 550 may be used with any standard clamp/hookstrip arrangement. These wire mesh layers 551, 552, 553 may be bonded together as a unit. The upturned ends 558 may be formed before or after bonding. Preferably the front and rear edges of the screen 550 are encapsulated by adhesive or glue as in the screen 430 and plugs 557 plug screen ends as do the plugs 437. The wire mesh lower layer 559 inhibits flexing of the screen 550 during use and increases longevity of the screen 550. The perforated corrugated plate 554 reinforces the screen 550 further. It is within the scope of the invention for a perforated corrugated plate to be used with any of the screens disclosed herein . Referring to Fig. 6 there are shown free latch levers 639 one in a "down" locking position (the one to the left in Fig. 6A) locking a screen 130, 230, 330 to the shaker basket and one in an "up" position from which it is releasable to release the screen from the basket. In use, the free latch levers 639 clamp the screen 130, 230, 330 between a top bar 135, 235, 335 and one of an adapter bar 140, 240, 340 and a wear or seal strip (not shown) of known shakers. Referring to Fig. 7A - 7D there is shown a releasable screen locking mechanism 770 for releasably holding a screen to a basket of a vibratory separator, for example, a screen 130 with its adapter bars and top bars is positioned on respective basket ledges (not shown) . As shown in Fig. 7A the releasable screen locking mechanism 770 releasably holds the screen 130 in place by clamping the screen 130 between the top bar and the adapter bar. As shown in Fig. 7B, the releasable screen locking mechanism 70 is in an "unlock" or release position permitting the screen 130 (not shown) to be removed from or inserted into the shaker basket. The releasable screen locking mechanism comprises a body 771 which has a bracket 772 bolted to a shaker basket wall with bolts (not shown) through holes 773 or appropriately secured to another part of a shaker . The body 771 has a hole 774 through which movably extends a rod 775. Leaf spring 776 are secured to the body 771. The rod 775 is pivotably mounted to a bar 777 with a pin 778. A distal end of the bar 777 is pivotably mounted around a pin or pivot member 779 mounted to the leaf springs 776. Bolts 781 secured to the pivot member 779 movably extend through holes 782 in leaf springs 776 and nuts 783 prevent the bolts 781 from escaping from the holes 782 in the leaf springs. The pivot member 779 fits through the bar 777. In both over and under centre positions, the bar 777 is releasably biased in place. A first "locked" position of the releasable screen locking mechanism 770 is shown in Fig. 7A. In the first "locked" position, a lower end of the rod 775 bears against a top bar of the screen 130 to releasably hold the screen 130 in a shaker basket. A second "locked" position is shown in Fig. 7B in which the screen 130 can be removed from or inserted into the shaker basket. Referring to Fig. 8 there is shown another releasable screen locking mechanism 886 for releasably holding a screen to a shaker basket. For example, a screen with its adapter bars and top bars is positioned on a basket ledge (not shown) . The releasable screen locking mechanism 886 is shown with a bar 887 and plunger 888 in an unlocked position, a locked position indicated by the bar 878 and plunger 888 in dotted line. A body 889 includes a shaker basket mounting bracket 891 with bolt holes 872 and holes 893 through which movably extends a rod 894 of the plunger 888. The rod 894 is pivotably secured to the bar 878 with a pin 896 and a distal end of the bar 878 is pivotably mounted about a pivot member 897. A spring 895 urges the plunger 888 downwardly and is biased to help maintain the apparatus in a releasable "locked" position. A spring stop 899 is on the rod 894.

Claims: CLAIMS : 1. A screen assembly for a vibratory separator, the screen assembly comprising at least one wire mesh screen (130; 260; 330) formed with undulating mesh material having a series of ridges spaced apart by a series of valleys , and a first series of spaced apart rods (136; 266; 336), the arrangement being such that, in use, the wire mesh screen is supported by the first series of spaced apart rods . 2. A screen assembly as claimed in Claim 1, wherein said first series of spaced apart rods (136; 266; 336) extend in a direction which is transverse to the ridges and valleys of said at least one wire mesh screen (130; 260; 330) . 3. A screen assembly as claimed in Claim 1 or 2 , further comprising a second series of spaced apart rods (265) arranged, in use, to support said first series of spaced apart rods . 4. A screen assembly as claimed in Claim 3, whe rein said second series of spaced apart rods (265) extend transverse to said first series of spaced apart rods (266) . 5. A screen assembly as claimed in Claim 1 , 2 , 3 or 4 , wherein said first series of spaced apart rods (336) are corrugated. 6. A screen as sembly as claimed in Claim 1 , 2 , 3 or 4 , wherein said first series of spaced apart rods have a corrugated surface . 7. A screen assembly as claimed in any of Claim 1 to 6, wherein the at least one wire mesh screen comprises a plurality of two or more wire mesh screens . 8. A screen assembly as claimed in Claim 7 , wherein the plurality of wire mesh screens (131, 132, 133; 261, 262, 263; 331, 332, 333) are adhered together. 9. A screen assembly as claimed in any preceding Claim, wherein the at least one wire mesh screen includes at least one upper wire mesh screen (131; 261; 331) having a first mesh size and a lower wire mesh screen (133; 263; 333) having a mesh size coarser than the first screen mesh size . 10. A screen assembly as claimed in any preceding Claim , further comprising a pair of spaced apart top bars (135; 267; 335) , one top bar on each side of the screen assembly at an outer edge thereof. 11. A screen assembly as claimed in any preceding Claim, wherein the undulating shape of the at least one wire mesh screen forms a series of end openings on two sides thereof, and further comprising plug apparatus (137; 269; 337) for, in use, plugging said series of end openings . 12. A screen assembly as claimed in Claim 11 , wherein said series of end openings are encapsulated in encapsulating material (142; 342) . 13. A screen assembly as claimed in any preceding Claim, further comprising a perforated corrugated plate (334) which supports said at least one wire mesh screen (330) . 14. A screen assembly as claimed in Claim 13, wherein the at least one wire mesh screen is adhered to the corrugated perforated plate. 15. A screen assembly as claimed in any preceding Claim, further comprising an adapter bar (140; 268; 340) on which the at least one wire mesh screen is mounted, the adapter bar having recesses (141; 264'; 341) for receiving the first series of spaced-apart rods . 16. A screen assembly as claimed in Claim 15, further comprising a layer of seal material (144; 268'; 344) on top of the adapter bar. 17. A screen assembly for a vibratory separator, the screen assembly comprising at least one wire mesh screen (450; 550) formed with undulating mesh material having a series of ridges spaced apart by a series of valleys, and a layer of wire mesh material (459; 559), the arrangement being such that, in use, the at least one wire mesh screen is supported by the layer of wire mesh material . 18. A screen assembly as claimed in Claim 17, wherein said layer of wire mesh material has a coarser mesh than said at least one wire mesh screen. 19. A screen assembly as claimed in Claim 14 or 15, further comprising a perforated corrugated plate (554) which supports said at least one wire mesh screen (550) . 20. A screen assembly as claimed in Claim 19, wherein the at least one wire mesh screen is adhered to the corrugated perforated plate . 21. A screen assembly as claimed in Claims 17, 18, 19 or 20. wherein the at least one wire mesh screen comprises a plurality of two or more wire mesh screens . 22. A screen assembly as claimed in Claim 21, wherein the plurality of wire mesh screens (451, 452, 453; 551, 552, 553) are adhered together. 23. A screen assembly as claimed in any of Claims 17 to 22 , wherein the at least one wire mesh screen includes at least one upper wire mesh screen (451; 551) having a first mesh size and a lower wire mesh screen (453; 553) having a mesh size coarser than the first screen mesh size. 24. A screen assembly as claimed in any of Claims 17 to 23, further comprising a pair of spaced apart top bars (450) , one top bar on each side of the screen assembly at an outer edge thereof. 25. A screen assembly as claimed in any of Claims 17 to 24, wherein the undulating shape of the at least one wire mesh screen forms a series of end openings on two sides thereof, and further comprising plug apparatus (457; 557) for, in use, plugging said series of end openings . 26. A screen assembly as claimed in Claim 25, wherein said series of end openings are encapsulated in encapsulating material . 27. A screen assembly as claimed in any of Claims 17 to 26, wherein the at least one wire mesh screen has opposed spaced-apart front and rear edges encapsulated in encapsulating material . 28. A vibratory separator fitted with a screen as claimed in any preceding Claim, wherein said screen assembly is not mounted in a frame 29. A releasable locking device (770; 886) for securing a screen assembly to a vibratory separator, which releasable locking device comprises an arm (777; 878) movable between a first position and a second position, a plunger (775; 894) pivotally connected to said arm for, in use, retaining said screen assembly to said vibratory separator in said first position and releasing said screen assembly from said vibratory separator in said second position, and first spring means (776) for, in use, inhibiting movement of said arm from said first and second positions . 30. A releasable locking device as claimed in Claim 28, further comprising second spring means (895) for, in use, inhibiting movement of said arm from said first position.

Inventors: ADAMS THOMAS COLE, GRICHAR CHARLES NEWTON, LARGENT DAVID WAYNE, LEONE VINCENT DOMINICK, MCCLUNG GUY LAMONT, MURRAY HECTOR M, SCHULTE DAVID LEE, SEYFFERT KENNETH WAYNE, WALKER JEFFREY EARL, ADAMS, THOMAS, COLE, GRICHAR, CHARLES, NEWTON, LARGENT, DAVID, WAYNE, LEONE, VINCENT, DOMINICK, MCCLUNG, GUY, LAMONT, MURRAY, HECTOR, M., SCHULTE, DAVID, LEE, SEYFFERT, KENNETH, WAYNE, WALKER, JEFFREY, EARL
Applicants: LUCAS BRIAN RONALD, TUBOSCOPE I P INC, LUCAS, BRIAN, RONALD, TUBOSCOPE I/P INC.
Application year: 1999
Main classification: B07B1
IPC codes: B01D33, B07B1