Abstract: A vibratory separator (in one aspect, a shale shaker) and methods for using it, the separator in certain aspects having a base, a basket movably mounted on the base, screen apparatus on the basket, material flowing onto the screen apparatus for treatment, at least a portion of the screen apparatus not inclined downhill (e.g. said portion horizontal or uphill), electromagnetic vibratory apparatus connected to the basket for vibrating the basket and the screen apparatus, driving apparatus for driving the electromagnetic vibratory apparatus, and control apparatus (on-site and/or remote) for controlling the driving apparatus and the electromagnetic vibratory apparatus; the material, in one aspect, being drilling fluid material with solids therein.

Abstract: The present invention concerns a vibrating screen having wear protections placed on beams of the vibrating screen. A supporting structure for screening media is placed on the beams. The wear protections are snapped onto adapters fixed to the beams. The adapters are fixed to the beams by an adhesive. The supporting structure includes support carriers fixed to transversal carriers. The transversal carriers are received in channels of the adapters.

Abstract: Apparatus is provided, in or for a screen separator for sieving materials, for clamping one or more sieve screen frames 78 within the confines of a chassis 40 of the separator to prevent egress of material from the separator. The apparatus comprises a sheath 50 extending around and embracing the chassis 40 and one or more expandable elements 66 for urging the sheath 50 against the chassis 40 and the screen frame(s) 78 to impart uniform clamping pressure to the clamped elements. The sheath 50 is designed to provide ease of mounting and release.

Abstract: A mount for a screen assembly, a screen assembly with such a mount, and a vibratory separator (e.g., a shale shaker) with such a screen assembly; the mount in certain aspects including a body with an inwardly projecting handle apparatus accessible when the screen assembly with such a mount is located in operation position on a mount structure of a vibratory separator.

Abstract: A sieve is disclosed which can, for example, be used in plansifters or similar sieving and screening devices for screening mealy or granular products. To increase screening performance, there is provided at least one drop-through channel whose width is, for example, at least 1.5 times that of known sieves.

Abstract: A mesh panel of the type having a plurality of spaced apart apertures includes an internal frame member substantially in the form of a perforated sheet, and having a plurality of openings therein larger than the apertures. The frame member has substantial internal rigidity. An elastomeric coating encapsulates at least a portion of said frame member. In a preferred embodiment, a bonding coating between the elastomeric coating and the frame member securely bonds to both the elastomeric coating and the frame member. The bonding coating is of the type that is liquid before application to the frame member and is curable by heat or time to a hard plastic. Preferably, the bonding coating is partially cured before the elastomeric coating is applied, after which both coatings are cured by heat. The panel is particularly well suited for use as a sorting screen.

Abstract: A screen element (2) of a screen (1) has longitudinal sides adapted to be arranged in a longitudinal direction of a screen frame (4) and transverse sides adapted to be arranged in a transverse direction of the screen frame (4). The transverse sides of the screen element (2) are provided with at least one projection (6) and/or at least one recess (7) for locking engagement, in a direction transversely to the plane of the screen element (2), with a corresponding projection (6) and/or recess (7) on neighbouring screen elements arranged in the screen frame (4). A screen (1) with a screen element (2) arranged in a screen frame (4) is also disclosed.

Abstract: A method and apparatus for separating material, particularly excavated material is presented. The method and apparatus utilize a releasable and interchangeable screen assembly which is positioned on top of a frame having a slanted grate. The screen assembly includes bar members which traverse the top of the screen and inverted hook members attached to a top surface of the bar members to enable an equipment bucket to engage the inverted hook members in order to lift and move the screen assembly.

Abstract: A screening assembly support frame includes a body member defining a longitudinal axis. The body member has a pair of parallel, spaced elongate support members with a spacer arrangement extending between the support members. An engaging formation, for engaging a screen panel of the screening assembly to be supported by the body member, is carried on each support member with the body member and the engaging formations being symmetrical about the longitudinal axis.

Abstract: A supporting structure for different screening media on a vibrating screen is disclosed, as well as a support carrier of the supporting structure. The supporting structure is received on a vibrating screen and has a number of support carriers arranged parallel to each other and perpendicular to a number of transversal carriers. The support carriers and the transversal carriers form a grid. The support carriers have grooves at each end to be snapped on and locked on circular ribs on top of the transversal carriers. The support carriers are made of a polymeric material and are elongated elements.

Abstract: A screen for a gyratory sifter including a frame having a plurality of cross-members and a rigid external extension. Additionally, the screen including a filtering element securably attached to the frame. Also, a method for installing a pre-tensioned screen in a gyratory sifter including inserting the pre-tensioned screen into the gyratory sifter. The pre-tensioned screen including a frame having a plurality of cross-members and a rigid external extension and a filtering element securably attached to the frame. Additionally, the method including mating the pre-tensioned screen to a ball box, wherein the mating includes placing the pre-tensioned screen against a contoured section of the ball box, and securing the pre-tensioned screen with a screen plate.

Abstract: An apparatus and method for separating material are described. A material separator may comprise a frame. The frame may comprise a base supporting a slanted grate deck. A reducer grate deck may be removably and pivotally coupled to the slanted grate deck. The reducer grate deck may comprise at least one internal locking member comprising a hole there through adjacent a bottom surface of the reducer grate deck.

Abstract: A screening machine for screening bulk material and the like comprising a housing and two sidewalls at which a screen deck is disposed, the screen deck comprising cross-members mounted on the sidewalls and longitudinal members which are mounted on the cross-members and receive an exchangeable screen lining. Said longitudinal members are clamped to the cross-members by means of removable mounting ties from two different directions.

Abstract: A vibratory separator having a basket for supporting screen apparatus for treating material, the basket pivotably mounted on a base, vibratory apparatus connected to the basket for vibrating the basket, the material forming a pool on the screen apparatus, and a beach formed on the screen apparatus, measurement apparatus connected to the basket and positioned above the screen apparatus for measuring a distance from the measurement apparatus to a top surface of the pool, control apparatus for controlling and in communication with the measurement apparatus for receiving signals therefrom indicative of said distance, which distance is indicative of pool depth at that location and which correspond to beach extent, and adjustment apparatus controlled by the control apparatus for adjusting angle of the basket, thereby adjusting extent of the beach.

Abstract: The invention provides a screen which has a screen body (12) and a plurality of ribs which extend across the screen body. Screening apertures (118) are defined in the screen body by the ribs. A reinforcing frame (124) is embedded in the screen body, which frame is made of a first plastics material which has a greater density than a second plastics material from which the screen body (12) is made. The frame has keying formations formed therein to assist in bonding between the frame and the screen body.

Abstract: A screening panel 10 comprises a peripheral frame 12 consisting of a pair of mutually laterally spaced side members 14, 16, which are integral with a pair of mutually axially spaced end members 18, 20. The side members 14, 16 and end members 18, 20 define corners of the panel 22.1, 22.2, 22.3 and 22.4 and the peripheral frame 12 where they meet. A plurality of mutually spaced ribs 15 extend across the periphery of the panel 10 to define a screening surface. The side members and end members are rectangular in cross-section, thereby defining substantially flat upper peripheral surfaces 12.1, outer peripheral surface 12.2 and lower peripheral surface 12.3 of the peripheral frame 12 and thus also the panel 10. The panel 10 includes locating recesses 24 provided at or near to the corners 22.1, 22.2, 22.3 and 22.4 of the panel 10. The panel 10 also has separate securing recesses in the form of semi-circular grooves 30 formed in the lower surface 12.

Abstract: A frame for a screen utilized in a shaker separator, the frame including: a first (2) and a second (4) longitudinal support member (2) spaced apart from and substantially parallel to the each other; one or more inner longitudinal support member (6), positioned between and substantially parallel to the outer longitudinal support members; a first (8) and a second (10) outer lateral support member (8), each being connected and substantially perpendicular to a corresponding outer longitudinal support member; a third outer lateral support member (12), connected and substantially perpendicular to the second outer longitudinal support member; a fourth outer lateral support member (14), connected and substantially perpendicular to the second outer longitudinal support member; one or more inner lateral support member (16), positioned between and substantially perpendicular to the first outer longitudinal support member and the second outer longitudinal support member and connected to the one or more inner longitudinal

Abstract: A screen assembly, holding apparatus for it, and a vibratory separator with it, the vibratory separator, in one aspect, for separating components of material introduced thereto, the vibratory separator including a basket, a collection receptacle beneath the basket, a deck on the basket for mounting a screen assembly thereon, the deck having a plurality of deck pins projecting upwardly therefrom, a screen assembly on the deck, the screen assembly including screening material, the screening material having a plurality of openings therethrough suitable for the flow of fluid therethrough, the fluid from the material introduced into the basket, the screening material having a plurality of spaced-apart screen holes therethrough, each screen hole having therein part of one of the deck pins, vibratory apparatus connected to the vibratory separator for vibrating the screen assembly, and holding apparatus for holding the screen assembly on the deck with a part of a deck pin in each screen hole.

Abstract: A screen assembly which includes a frame, a plurality of openings in the frame, a screen overlying the openings, a plurality of spaced tapered ribs on the opposite side of the frame from the screen, a first end on the frame with a lip, and a second end on the frame with a clip thereon. Another embodiment has a first end with a ledge and a second end with an overhanging portion, and a seal on the ledge.

Abstract: A screen assembly which includes a frame, a plurality of openings in the frame, a screen overlying the openings, a plurality of spaced tapered ribs on the opposite side of the frame from the screen, a first end on the frame with a depending lip, and a second end on the frame with a clip thereon. Another embodiment has a first end with a ledge and a second end with an overhanging portion, and a seal on the ledge.

Abstract: A screening panel 10 comprises a peripheral frame 12 consisting of a pair of mutually laterally spaced side members 14, 16, which are integral with a pair of mutually axially spaced end members 18, 20. The side members 14, 16 and end members 18, 20 define corners of the panel 22.1, 22.2, 22.3 and 22.4 and the peripheral frame 12 where they meet. A plurality of mutually spaced ribs 15 extend across the periphery of the panel 10 to define a screening surface. The side members and end members are rectangular in cross-section, thereby defining substantially flat upper peripheral surfaces 12.1, outer peripheral surface 12.2 and lower peripheral surface 12.3 of the peripheral frame 12 and thus also the panel 10. The panel 10 includes locating recesses 24 provided at or near to the corners 22.1, 22.2, 22.3 and 22.4 of the panel 10. The panel 10 also has separate securing recesses in the form of semi-circular grooves 30 formed in the lower surface 12.

Abstract: A support apparatus for supporting at least one screen assembly of a vibratory separator, the vibratory separator having seal apparatus for sealing an interface between a portion of the at least one screen assembly and an interior surface of the support apparatus, the seal apparatus including a seal member removably held by a seal holder within the vibratory separator, the support apparatus including container apparatus having a side wall, the side wall having an opening therethrough adjacent an end of the seal apparatus, and a cover removably connected to the side wall on an exterior surface thereof, the cover removable to provide access to the seal apparatus.

Abstract: A screen assembly 22 includes a conveyor 26 pivotably mounted beneath a screen 24 for segregation of fractions of material, for example from a mobile crusher 10. Hydraulic cylinders (not shown) are used to selectively move telescopic arms 48 (only one of which is shown in the Figures), to raise or lower the conveyor 26 between operative position and inoperative positions. In the operative position the conveyor 26 is substantially parallel to the screen 24 for receiving material which has passed through the screen mesh, in use. In the inoperative position the conveyor 26 is angularly displaced relative to the screen 24 about the pivot, to provide access to the underside of the screen 24, e.g. for maintenance purposes. Removable pins 50 are provided for releasably securing the attitude of the conveyor 26 relative to the screen 24 in the operative position.

Abstract: A method and apparatus for separating material, particularly excavated material is presented. The method and apparatus utilize a releasable and interchangeable screen assembly which is positioned on top of a frame having a slanted grate. The screen assembly includes bar members which traverse the top of the screen and inverted hook members attached to a top surface of the bar members to enable an equipment bucket to engage the inverted hook members in order to lift and move the screen assembly.

Abstract: Interconnectible screen assemblies for vibratory separators or shale shakers and methods for manipulating such screen assemblies which, in certain aspects, include a first screen assembly and a second screen assembly positioning at least a portion of the first screen assembly with respect to screen assembly holding apparatus, connecting a second screen assembly to the first screen assembly, and moving the first screen assembly and the second screen assembly together with respect to the screen assembly holding apparatus.

Abstract: A waste recovery station for a beach cleaner for recovering waste raked up by a beach cleaner. A waste recovery station for a beach cleaner includes a pair of station members arranged in parallel with each other through a required spacing. Each station member is provided with a pair of support posts with a foot such as, for example, a circular or square flat plate fixed to a lower end of each support post and is also provided with a guide member fixed to upper ends of the support posts. In the guide member, a longitudinally intermediate portion is formed as a horizontal portion and front and rear end sides are formed as slant portions and are bent downwardly at an obtuse angle. The beach cleaner A is lifted by the guide members while passing between the station members, whereby waste caught on rakes is allowed to drop onto the sand.

Abstract: A screen assembly for a vibratory separator having, in one aspect, a frame with a plurality of openings therethrough, screening material on the frame over the openings, the frame having an end area at a material exit end of the frame, and end apparatus at the end area for facilitating material movement over the end area; in one aspect, non-smooth areas on top of the screen assembly to impede solids movement on such areas and/or to direct them off such areas; vibratory separators with such a screen assembly; and methods of their use.

Abstract: A support for a screen assembly for a vibratory separator, a screen assembly with such a support, a vibratory separator with one or more such screen assemblies, and a method of using such a screen assembly, such a support having a body, a first series of holes through the body each hole having a first opening size as viewed from above, a second series of holes through the body each hole with a second opening size as viewed from above, the second series of holes at a selected area of the body and the support positionable in a vibratory separator so that the selected area is adjacent a selected location with respect to the vibratory separator, and the second opening size smaller than the first opening size and/or the second series of holes with holes spaced apart differently than the holes of the first series of holes; and in one aspect, a plastic grid with such hole series for fusing together layers of screening material.

Abstract: The present invention is a gravel screening device for separating different sizes of gravel and stones or separating gravel and stones from larger rocks. The device comprises a screen supported by a frame with two side walls connected by a low front wall. The screen and the upper edge of each side wall slope downward toward the low front wall. The frame is approximately 10 to 12 feet in width, about 8 feet deep, and supported about 8 feet high by the side walls in the back sloping toward the front wall which is about 4 feet high. The back is open and the edges of the side walls slope outward from the tops of the sidewalls to their bases, thus accommodating a maximum amount of gravel taking into account the angle of repose of the gravel collected in the device.

Abstract: A unibody structure for a screen assembly for a vibratory separator, and screens with such a structure, the unibody structure having, in certain aspects, an integral body member with a portion having a plurality of spaced-apart openings therethrough, the integral body member including side portions foldable to form a pair of spaced-apart integral side members, the integral body member having a plurality of spaced-apart support openings defining portions of the integral body member foldable to form a plurality of spaced-apart supports extending from a first side of the integral body member to a second side thereof and each support of the plurality of spaced-apart supports independent of each other support of the plurality of spaced-apart supports along its length.

Abstract: Methods for making a screen assembly for a vibratory separator, a screen assembly made by such methods, and a method for separating components of a fluid with a vibratory separator with such a scren assembly; the method in certain aspects including sewing together with sewing material at least two layers of screening material (e.g., two, three, four or more layers; e.

Abstract: A screen system employs a resiliently mounted housing, a vibration generator mounted to the housing, a mounting frame fixed to the resiliently mounted housing and a support surface. This system receives a screen including a screen frame and pre-tensioned screen cloth. The frame includes an inwardly extending mounting flange accessible from below the screen when placed in the housing. Clips pivotally mounted relative to the mounting frame include a first rounded lever extending upwardly to selectively engage the inwardly extending mounting flange. Second levers extend downwardly to cooperate with actuators. The actuators include inflatable bodies with contacts which, upon inflation, force the clips to engage the inwardly extending mounting flanges. This engagement retains the screen on a resiliently mounted housing and is able to further tension the screen in place.

Abstract: There is provided screen apparatus comprising side walls having a lower edge portion configured to accept tubular screen support members. An upper edge extends from the inlet end of the side walls to an apex from which a declining edge extends to the foot of the side walls. The lower edge, upper edge and declining edge are each provided with edge stiffening. A torque tube is secured between the respective exciter mount castings, the torque tube and stiffened side wall being selected to provide that the first fundamental frequency mode greater than the exciter frequency is at least 2 Hz greater than the exciter frequency and the first fundamental frequency below the exciter frequency is at least 2 Hz lower than the exciter frequency.

Abstract: A vibrating screen assembly having a tubular frame. The tubular frame includes a pair of opposed tubular sides and a pair of opposed tubular ends. An upstanding lip extending from each side and extending from each end forms a rim enclosure. A ledge extends inwardly from the opposed sides. A plurality of tubular cross supports and the opposed tubular ends rest on the ledge and are connected to the opposed sides. A perforated plate with a plurality of screen cloths thereon is positioned within the rim enclosure and secured to a planar surface of the frame. One of the ends includes an extending overhang while the other end includes a lower recess so that an overhang from one screen assembly will mate with a recess from another screen assembly to form a liquid tight seal.

Abstract: A screen assembly which, in at least certain aspects, has at least one wire mesh screen formed with undulating mesh material having a series of ridges spaced apart by a series of valleys, a corrugated perforated plate with an undulating shape corresponding to the undulating mesh material of the at least one wire mesh screen, the at least one wire mesh screen on the corrugated perforated plate, a series of spaced apart rods all of which are in one plane, the corrugated perforated plate mounted on the rods of the series of spaced apart rods, and each rod having a length and independent of and not connected to the other rods along its length by any member in the same plane as the rods, each rod having two spaced apart ends.

Abstract: A sieving device with a vibratory supporting frame and a vibration frame which is held against said supporting frame so as to be able to vibrate freely. A simple, compact design which provides good sieving and conveying performance is achieved in that the vibration frame is spring-elastically coupled to the supporting frame by torsion-bar-like spring elements.

Abstract: A support strip has been invented for supporting part of a screen used in a vibratory shaker, the support strip having a support body having spaced-apart ends spaced-apart sides, and a top surface, and at least one hump, raised portion or upturned finger projecting above the top surface of the support body and a support beneath said at least one hump, etc. The support may be entirely beneath the hump, etc. or part thereof may project beyond the hump, etc. The present invention also discloses a variety of screens and screen assemblies with such structure.

Abstract: The invention relates to a sieve frame for plan sifters and also to a method of producing it. It is used mainly in plan sifters for milling. The object is to improve the functionality of an insertable sieve frame and to simplify production.

Abstract: The present new, improved rock screed bucket has a solid rectangular back plate together with a framework having a rectangular bottom and a pair of generally triangular shaped sides. The solid rectangular back plate acts as a backstop. The rectangular bottom supports a heavy duty grading screen. A mounting frame is mounted to the rear of the solid rectangular back plate through a plurality of shock absorbing spacers. The conventional arm structures and conventional hydraulic system of a conventional tractor or skid loader connect to the mounting frame. By rapidly moving the conventional arm structure and conventional hydraulic system any material in the rock screed bucket can be shaken and thus screened. In a second embodiment, a hydraulic shaker may be attached to the top of the rock screed bucket to shake the rock screed bucket. The hydraulic shaker is conventional and derives its power from the conventional hydraulic system of the tractor or skid loader.

Abstract: A mounting structure for a screen frame and/or a top cover to a vibratory frame of a screening machine requires only an initial one time adjustment and includes a pair of elastomeric restraints each including a compressible bumpers on a head-end of the screen frame or top cover and a pair of compressible rollers on a foot-end of the screen frame or top cover. The screening machine mounting structure accounts for the manufacturing tolerances between the screen frame or top cover and the vibratory box frame to provide a snug fit. The rollers allow for easy screen frame or top cover installation and removal and prevent metal-to-metal contact between the respective components which generates wear and noise during operation. Further, the mounting structure according to this invention can be retrofittable into existing screening machines as well as being original equipment and is useful for securing other components of the screening machine in addition to the screen frame and top cover.

Abstract: A screen is disclosed which, in certain aspects, has screening material between opposed frame sides and one or more lower strips beneath the screen. In one aspect these strips are only inteconnected via their ends and not along their lengths. In certain aspects, a plurality of lower strips are bonded to the screen and extend across the screen from one frame side to the other. In one aspect one or more of the strips has one, two, or more humps or ridges corresponding to one or more corrugations in a corrugated perforated plate and/or corrugated screen assembly which is on the plate or, with no plate present, on the strips. In another aspect instead of the strips a solid corrugated perforated plate is used. In one aspect openings or perforations through the plate are triangular. In one aspect the screen is undulating screening material and lower portions of the screening material are bonded to a plate or to strips. Optionally screen mounting hooks or frame edges or screen edges may be used with such screens.

Abstract: A screen cylinder, screen, method of manufacture of the screen cylinder, and method of use of the screen cylinder, allow screen capacity to be maximized without sacrificing screen cylinder strength, and while achieving a clean accepts flow. A screen cylinder is constructed in a conventional manner except that at least one reinforcing ring is permanently fastened (typically by continuous or spot laser or electric beam welding, or direct resistance welding) to at least a majority of (and typically essentially all of) the land areas which separate grooves in a row from each other, at the outlet surface of the cylinder, or at least one spiral ring is applied. In this way effective slot length of screen cylinders may be about 65-90% of the total screen length, compared to only about 45-55% for conventional screen cylinders. The screen cylinders are particularly effective in screening cellulose pulps from the pulp and paper industry.

Abstract: A modular deck support framework system employing support tray framework sections for vibrating screens having an essentially rectangular outlined perimeter framework. Each support tray perimeter framework has at least: two opposed side framework members and a square cut cross-angle 50, or notched end angle 62, as a feed end cross framework member; and a square cut flat stock 52 or curved top flat stock 52C as a discharge end cross framework member. Square cut cross-angle 50 is oriented such that square cut cross-angle upper leg 50U is pointing essentially upwards and essentially perpendicular to the flow of particles over support trays, and square cut cross angle lower leg 50L is pointing essentially with the flow of particles over support trays. Notched end angle 62 is oriented similarly whenever employed.

Abstract: This improved screening apparatus for sorting various size aggregates utilizes a screen made of polyurethane having two sets of perpendicular evenly spaced parallel webs each of which enclose a wire provided for reinforcement. If desired, the reinforcing wires can be single or multiple through either one or through both sets of webs. Web segments extend between web intersections. Areas enclosed by opposed adjacent web segments provide for the screen openings. This area can contain either a single hole or a plurality of holes to provide a number of different screen sizes. The holes increase in cross-section from the screen aggregate input side to the output side to eliminate or greatly minimize particles wedging within the holes. Backing bucker bars of various widths attached to the lower side of the screen provide a predetermined screen cross-section when their lower edges are supported horizontally.

Abstract: A support structure for thin screenplates utilized for fine screens in Fibresaving applications for pulp fiber suspensions or the like wherein a support structure having a screen support in minimum screen contact positioned by a support reinforcement and positioning device, assembled to form an integral structure which reduces the stresses and deflections in the thin screenplates occurring in operation.

Abstract: A vibratory screen system including a screen assembly having screen cloth on both the top and the bottom of the frame. The screen cloth on the bottom has openings larger than and up to five times the size of the openings on the upper screen cloth. A pattern of dividers divide the screen into compartments. The screens are bonded to the frame and to the pattern of dividers.

Abstract: A screen assembly for a vibrating shaker having a crowned deck for receiving at least one screen assembly thereon and a plurality of attachment members. The screen assembly includes a rigid frame having a pair of parallel, opposed sides and a pair of parallel, opposed ends. An underside of the frame is radiused to match the crowned deck of the shaker. A top planar side of the rigid frame is opposed to the underside of the frame. At least one screen cloth layer is fixed to the planar top side of the frame for separating solid materials from liquids and fine solid particles.

Abstract: A screening system, preferably a finger screening system, for screening particulate material is provided.

Abstract: A method and apparatus for mounting a panel on a rail member having first and second resilient legs separated by a channel. A groove disposed along a first side of the panel receives a portion of one of the resilient legs of the rail member. The groove extends from a lower surface of the panel toward an upper surface of the panel so that the upper surface extends over the resilient leg received in the groove. The groove includes a first side surface with a first inclined portion and a second side surface with a second inclined portion. The second side surface of the groove is engagable with the inner leg surface of the resilient leg received in the groove to outwardly urge the resilient leg away from the channel of the rail member and toward the first inclined portion of the groove to retain the panel on the rail member.

Abstract: Sieve with slots or holes, made from a U-shaped section, constituted by a stack of identical circles, each circle (1, 1') being made from a tapered U-shaped section of which the two ends are welded or mechanically connected to one another, characterized in that this stack of circles (1, 1') is maintained tightly between two rings (2-3, 2-'3') by a plurality of tie rods (4, 4') and in that the lateral walls of the circles in the stack rest on one another without any further fastening together, so that the walls of the sections can undergo elastic deformation under the effects of the tightening.