The prior art discloses a variety of apparatus and devices for securing a screen to a vibratory screening apparatus. Many of the prior art systems employ a single bolt, nut and plate combination, with or without shock absorbing material. Exemplary prior art patents include, but are not limited to, US-A-4,303,509; 5,332,101 and 5395925.

US-A-5,332,101 explains that in vibratory screening apparatus,. the screens wear out and require replacement.

The edges of a screen are attached to draw bars, draw bolts are engaged to the draw bars at intervals along their length, and nuts attached to the draw bolts can be tightened to tension the screen. This arrangement suffers from the problem that without a torque wrench there is no accurate way to adjust the magnitude of the tension applied to the draw bolts. Commonly the draw bolts apply different tensions at various points along the length of the draw bar, so that an uneven tension is applied to the screen. In addition, on a machine having three screens there are usually 24 draw bolts. Each draw bolt is tightened by a nut which has to be turned through a number of rotations during both the tightening and the loosening procedure, which is extremely time-consuming.

Since the flow of material can not be stopped during screen change, the longer it takes to change the screens, the greater is the loss of material which could have been screened. This is particularly critical in the oil

drilling industry where the loss of drilling mud which can be reclaimed is directly proportional to the time required to change the screens. The solution which was put forward is to provide a quick release bolt comprising a bolt member having first and second end portions and a central portion therebetween, first and second members mounted on the central portion of the bolt member, and cam means and cam follower means effectively positioned between the first and second members for causing the first and second members to occupy relatively close and relatively remote positions with respect to each other.

Means on the first end portion of the bolt member enables a pulling force to be exerted on an external member.

Spring means mounted relative to the first and-second members causes the bolt means to exert the pulling force on the external member when the first and second members are in the relatively remote position (the locked state of the device) and to release the pulling force when the first and second members are in the relatively close position (the unlocked state of the device).

There are a number of disadvantages associated with commercially available embodiments of the above quick release draw bolt device. The movable adjustment nut may require a special wrench to turn it. Often the nut can only be effectively adjusted when the device is in its unlocked state. The sliding surfaces require regular lubrication, otherwise they may gall, making high torque necessary. The high wrench load required can result in a bent tension bolt. Furthermore if the springs collapse (take a set) the tension load produced by the spring becomes reduced and insufficient tension may be applied to the screen. Often the only way to achieve the required tension in these circumstances is to collapse the spring completely and to torque the spring adjusting nut.

A problem with which the invention is concerned is

to provide a quick release draw bolt device in which the above problems are reduced or avoided. Another problem with which the invention is concerned is to provide a quick release draw bolt device that can be used with existing vibratory system screen mounts without requiring changes to the vibratory system. A further problem with which the invention is concerned is to provide a quick release draw bolt device which is adjustable when in its locked state. A yet further problem with which the invention is concerned is to provide a quick release draw bolt device in which misalignment between the screen and structural members of the vibratory system can be reduced or avoided.

That problem is solved, according to the invention, by providing a toggle linkage to control the spacing between the first and second members, said linkage preferably passing an over-centre position between the locked and the unlocked states of the clamp.

In one aspect the invention provides a quick release clamp for securing a screen to a vibratory screen apparatus, said clamp comprising: a bolt having a head, a threaded tail and a central portion between the head and the tail; first and second members through which the central portion of the bolt extends, the first member being for abutment with a portion of the vibratory screen apparatus, the head of the bolt projecting from the first member, and the tail of the bolt projecting from the second member; means connecting the first and second members and operable to cause them to move between relatively close and relatively remote relative positions; and an adjustable nut on the tail of the bolt for transmission of load to the second member when the first and second members are in their relatively remote

position characterised in that said connecting means comprises first and second links pivoted together and respectively pivoted to the first and second members.

In another aspect the invention provides screening apparatus comprising: a screen mounting basket; at least one screen mounted to the basket; and at least one clamp as aforesaid clamping at least one edge of the screen to the mounting basket.

The apparatus may further comprise one or more vibratory devices for vibrating the basket and/or the screen. The invention can be used to attach screens with integral tension rails or side members to vibratory screening apparatus.

In a third aspect there is provided a method of clamping a screen to a vibratory screen system having a screen mounting member, said method comprising placing a screen on or in the mounting member and attaching the screen to the mounting member by one or more clamps as aforesaid.

A preferred form of the quick release clamp has a front grip plate which is releaseably securable to a typical side mount on a vibratory screen system. A first locking link provides a rotatable mounting for the front grip plate and a second locking link is pivoted to the first locking link and has a swivel rotatably mounted to it. Movement of the links controls the spacing between the grip plate and the swivel, and the links are arranged to be movable"past centre"or"over-centre"to provide a stable locked mode for the apparatus. A bolt is provided which extends through the swivel, both links and the front grip plate, and which has a further portion which in use extends through the side mount and projects beyond a screen tension rail or screen mounting member. One end

of the bolt abuts the tension rail so that tightening of a nut at the other end of the bolt increases the tension on the screen. Such tightening can be carried out after the first and second locking links have been moved to contact one another in a locked but releaseable position.

The swivel or second member which is pivoted to the second link permits the first and second links to align with the bolt and reduces or eliminates binding of the grip plate with the side mount of the vibratory screen apparatus.

One or both of the links may be provided with typical wrench flats, bosses or recesses so that off-the shelf wrenches may be used to move the links apart and together between their locked and released states. To provide tension for the bolt, a spring or springs may be provided at any suitable location within the clamp, for example between the nut and the second member or swivel, or between the first member or grip plate and an enlarged portion of the bolt. The spring or springs may take the form of spring discs between the nut and the second member or swivel, and a single spring disc may be used or there may be two, three or four or more such discs.

Suitable spring discs or flange belleville springs are commercially available.

How the invention may be put into effect will now be described, by way of example only, with reference to the accompanying drawings in which: Figs. 1A and 1B are top and side views of a first embodiment of the quick release clamp, and Figs. 1C, 1D, 1E and 1 F are respectively a top view, an end view, a bottom view and the other end view of a body forming part of the clamp of Fig. 1A; Fig. 2A is a side view of part of the clamp of Fig.

1A in a collapsed unlocked state, Fig 2B. is a view of the clamp in position on a basket sidewall showing part

of the screen, tension rail and basket sidewall, and Figs. 2C and 2D correspond to Figs. 2A and 2B but with the clamp in its expanded locking state; Figs. 3A and 3B are a side sectional view and an end view of a swivel forming part of the clamp of Fig. 1A; Figs. 4A and 4B are a side and a bottom view of one of the links forming part of the body of the clamp; Figs. 5A-5C are a side, an end and a bottom view of the other of the links forming part of the body of the clamp; Figs 6A-6D are a side view, an end view, a bottom view and a partial side view of a plate forming part of the body of the clamp; Fig. 7 is a perspective view of a vibratory screen apparatus according to an embodiment of the invention; Fig. 8 is a side view of another vibratory screen apparatus according to another embodiment of the invention; Fig. 9A is an exploded perspective view of a further embodiment of a vibratory screen apparatus according to the invention and Fig. 9B is an enlarged view of part of the apparatus of Fig. 9A; and Figs 10A-10E are views corresponding to Figs 1A, 1B, 6A, 6B and 6D of a second embodiment of a quick release clamp according to the invention.

In Figs. 1A-1 F, a quick release clamp 10 according to the invention comprises a bolt 60 that extends through a clamp body defined by a first member or plate 20, a first link 30, a second link 40 and a second member or swivel 50. A nut 66 is engageable onto a threaded rear end of the bolt 60 to hold the bolt in position and spring washers 64 fit onto the bolt 60 between the nut 66 and the swivel 50.

Referring to Figs. 1A, 2B and 2D, the bolt 60 which is used in existing quick release bolts has at one end a

head 61 which is flattened so that in this embodiment its width is greater than that of shaft portion 68 as apparent in Fig. 1A and its depth is the same as that of shaft portion 68 as seen in Fig 1B. The purpose of the clamp is to attach a screen 93 to basket sidewall 91 of a vibratory screening apparatus. The screen 93 has a hook formation along its edge adjacent the sidewall 91 and a- tension rail 92 is engaged in the hook formation and is formed with slot-like apertures 95 spaced apart at intervals along its length. In one angular position of the bolt shown in Fig. 2B the head 61 is aligned with the longer direction of an aperture 95 so that it and a portion of the shaft portion 68 mat be passed through the aperture. Rotation of the bolt 60 by 90o about its axis brings it to the angular position shown in Fig 2D where the head 61 is normal to the longitudinal direction of the aperture 95 and engages the inner surface of the rail 92 so that tension in shaft portion 68 is transmitted to the rail 92. Partway along the shaft portion 68 the bolt has an enlarged portion 62 for limiting rearward travel of the bolt, the portion 62 being abuttable against the inner surface of the sidewall 91. Behind the enlarged portion 62, the bolt shaft has another plain portion 63, a first threaded region 65, a second plain region 67 and a second threaded region 69. An 0-ring or other sealing member 69a fits onto the shaft portion 63 and seals against the enlarged portion 62. The bolt 60 can be passed through a channel 23 which extends through the body of the clamp, and on its rear end there can be fitted the spring washers 64 and the nut 66.

The body of the clamp includes front plate 20 which is shown in more detail in Figs 6A-6D and which may made inexpensively by investment casting. The front plate comprises a plate member having front and rear faces.

From either side of the front face there project arms 28

for releaseably encompassing a mounting plate 18 on the basket sidewall 91. A member having an arm portion 24 and a lip portion 27 extends partway across the top front edge of the plate 20, these portions being are disposed, configured and dimensioned so that the member may be hooked onto a flat part of the mounting plate 18.

The channel 23 opens through the front face of the plate 20 and surrounding that opening there is a recess 23a within a raised portion 25 which fits into a corresponding recess in the plate 18. An O-ring or other sealing member may be used to seal the interface between the raised portion 25 and the plate 18. A ridge 21 extends across the front face of the plate 20 to either side of the raised portion 25, and is disposed, configured and sized so as to pivot against the flat outer face of the plate 18. The ridge 21 permits the body of the clamp to align itself with the tension bolt 60 and inhibits binding of the bolt against parts it may contact. Instead of the ridge 21, there may be employed two spaced apart nodules, one on either side of the raised portion 25, or there may be a series of three or more nodules across the plate. An optional cylinder 29 projects from the rear face of the plate 20 and the channel 23 extends all the way through the plate 20 to the rear of the cylinder 29. As will be discussed below, the rear end of the cylinder 29 provides a stop which limits movement of the swivel 50. In those embodiments where the cylinder 29 is not present, the bolt 60 has more freedom of movement e. g. for alignment. Pinion holes 19 are located to either side of the plate 20.

The first link 30 is shown as an individual component in Figs. 4A and 4B and may also be made inexpensively by investment casting. It comprises a pair of arms 36 and a bar 38 which extends between and interconnects the arms 36. The forward ends of arms 36

have holes 34 therethrough for pinions 22 which locate into the holes 19 to pivot the front end of the first link 30 to the plate 20. The pinions may be made of any suitable material including hardened steel and stainless steel. The link 30 is movable to bring the bar 38 into abutment with the arm 24 of the plate 20, but the bar 38 may be dimensioned and configured so that it can pass- above the arm 24. In the embodiment shown the arms 36 space the bar 38 from the cylinder 29 of the plate 20 so that the bar 38 does not touch the cylinder 29.

Alternatively the cylinder may extend further from the plate 20 than is shown in Figs. 1A, 2A and a recess may be provided in the bar 38 to accommodate the cylinder 29.

A wrench boss 31 projects from one of the arms 36 for use with any typically known commercially available wrench.

Alternatively a hexagonal recess for an Allen wrench or a "star"recess for a wrench of corresponding type may be used. As a further alternative a simple hole or projecting surface may be provided for engagement manually, by a hook or by other similar devices. In a further alternative wrench bosses or bars may be provided on both arms 36. The rear ends of the arms 36 are formed with through holes 35 and pinions 32 extend through the holes 35 to movably connect the first link 30 to the second link 40. As discussed below, a rear surface 37 of the bar 38 serves as a stop for a corresponding surface of the second link 40. With the bolt 60 removed, the first link 30 can rotate about the pinions 22 past the longitudinal axis of the cylinder 29.

The second link 40 is shown as an individual component in Figs. 5A and 5B and may also be made by investment casting. It has two arms 48 with holes 44 through them for the pinions 32. The arms 48 are disposed within the arms 36 of the first link 30. A bar 47 interconnects and extends between the arms 48. A front

surface 49 of the bar 47 is movable as the arms 48 rotate about the pinions 32 to abut and stop against the rear surface 37 of the first link 30. A wrench boss 41 is engageable with commercially available wrenches to move the second link 40 The wrench boss 41 may be replaced and/or used with any of the alternatives discussed above for the wrench boss 31 of the first link 30. The second link has rear arms 45 provided with holes 46 for pinions 42 that movably connect the second member or swivel 50 to the second link 40. A cut-out portion 41 of the bar 47 provides a space within which part of the swivel 50 can rotate as discussed below.

The swivel 50 is shown individually in Figs. 3A and 3B. It has two arms 51 formed with holes 56 through them for the pinions 42. A member 57 accommodates a bolt 60. A recess 58 surrounds the hole 54 and its inner surface 55 provides a stop for the nut 66. Alternatively, depending on the size of the nut 66, the rear surface of the member 57 can serve as a stop for the nut 66. The surface 49 of the second link 40 may be slanted downwardly from left to right as viewed in Fig. 5B to permit full 360o rotation of the swivel 50 about the pinions 42, but this degree of rotation is more than is needed and a rotational travel that allows movement of the clamp between its fastening and its released states will be sufficient. The hole 54 may have a diameter slightly larger than the outer diameter of the bolt 60 to permit some movement of the bolt 60 with respect to the walls of the hole 54.

Figs. 2A and 2B show the clamp 10 in a release position where the screen 93 has not been tensioned by the action of the clamp on portions of the vibratory screening apparatus and the links 30,40 are collapsed.

The head 61 of the bolt is in the rotational position where it can be inserted into or removed from the aperture 95 in the tension aril 92. Arrows on the links

in Fig. 2A show how the links are to be moved to go to the extended or locking state shown in Figs. 2C and 2D.

Furthermore, the bolt 66 has not been tightened against the swivel 50.

As shown in Figs. 2C and 2D, the bolt 60 has been rotated so that its head 61 is held against the inner surface of the rail 92, and the links 30,40 have been rotated to the extended locking position of the clamp.

The nut 66 has been tightened (rotated and moved to the left as viewed in Fig 2D) The screen 93 has now been pulled against a stop 94 secured to or formed integrally with the basket sidewall 91 and the top of the tension rail 92 has been moved to abut the inner surface of the basket sidewall 91. As shown in Fig 2D the pinions 32 are now disposed below a line L connecting the pinions 22 and 42. The surface 49 of the bar 47 of the second link 40 has stopped against the surface 37 of the bar 38 of the first link 30. Due to the"below centre"position of the pinions 32, the links 30,40 are releaseably locked together and transmit load between the plate 20 and the swivel 50. By using appropriate wrenches on the bosses 31,41, the links may be selectively moved apart to selectively unlock them, permitting release of the screen 93 from the basket.

The size and configuration of the bolt 60, in combination with the springs 64 and the nut 66 permits adjustment of tension applied to the screen 93 after the links 30,40 are moved to the closed extended position of Figs. 2C, 2D.

In an alternative construction, the pinions 22,32, 42 may be located and the stop surfaces of the links may be located so that the links meet"above centre"for easier opening of the links.

Fig. 7 shows a vibratory separator apparatus 110 in which a plurality of clamps 10 according to the invention

releaseably secure screens S and T within a basket B. One such vibratory separator apparatus (but with a different scerrn securement apparatus) is disclosed in US-A- 4,735,712, the disclosure of which is incorporated herein by reference.

Fig. 8 shows a vibratory separator apparatus 120 in which a plurality of clamps 10 according to the invention are used to releaseaably secure screens V within a basket C. One such vibratory separator apparatus (with a different screen securement apparatus) is disclosed in US-A-4,882,054, the disclosure of which is incorporated herein by reference.

Figs. 9A and 9B show a vibratory separator apparatus 200 according to the present invention in which there are two screen baskets 2022,204; vibrator apparatus 206, 208, heater beds 210,212 one under each basket; heat transfer plates 214; heated fluid supply line 220 and fluid return line 222. A plurality of clamp assemblies 10 according to the present invention hold a screen or screens (not shown) in the baskets 202,204. The clamps 10 are shown in place on the top basket 202; clamps 10 are connectable to but are not shown on the lower basket 204. The lines 220 and 222 are connected to and in fluid communication with a heated fluid generating system e. g. a steam boiler system G. Steam flows in via the line 220 to heat exchange bed 210 and cooled fluid returns via the line 222 which flows to a condenser CN and is pumped by a pump P back to the system G. The bed 212 may have its own system G or the system G may be common to the two beds.

Similarly the heat transfer plates 214 have their own systems SY with supply line L and return line M, but the heat transfer plates may instead be tied into the system G.

The apparatus described above may be used to screen drilling mud and the system G may be used to raise the

temperature of the mud G or other fluid medium introduced into the apparatus up to at least 70oF (21oC), preferably to at least 80oF (27oC) and more preferably to at least 90oF (32oC). Any suitable heat exchange system may be used instead of the system G.

Figs. 10A-l0E show an alternative embodiment 300 of the clamp 10 and like numerals indicate the same parts.- The cylinder 20 of the clamp 10 is deleted and an area 312 for an O-ring is larger than the recess 23 for the clamp 10. A ridge 304 encircles the area 302. A washer 306 is used with the nut 366.

It will be appreciated that modifications may be made to the embodiments described above without departing from the spirit and scope of the invention.