GB2437602A

GB2437602A - Screed level

Info

Publication number: GB2437602A
Application number: GB0608472A
Authority: GB
Inventors: Jose Fernandez; Sujeyanthan Javaratnasingam
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-04-28
Filing date: 2006-04-28
Publication date: 2007-10-31
Also published as: GB0608472D0

Abstract

The invention relates to a scraper bar 10 for screed levelling comprising a hollow tapered or wedge profiled section with a rounded or bull nose working edge (17 figure 1b) that contacts the screed. The scraper bar may be made from aluminium and further comprise a demountable operators handle 15 fitted to a demountable bar clamp (29 figure 2a) and preferably include visual reference markings for blade angle alignment. A later embodiment relates to a screed levelling kit comprising said scraper bar with a plurality of reference bars (12 figure 5) and support pegs (13 figure 50) that support the reference bars and on which the scraper may rest and level the cement to the desired height. The reference bars may be rectangular and may incorporate connector elements (28 figures 4a-d).

Description

* S S * a I S S * I $ I II I S *S Screed Level This invention relates

to screed level tools and (on-site) screed levelling, in building and construction.

Terminology -Screed A screed is generally a top layer of finer grade, particulate material applied over a coarser aggregate base-grade to a desired wearing depth and level of flatness -either straight and level or to a prescribed slope.

Concrete Floor A (floor) screed is thus a suitable surface for finish, sealing, painting or 1 0 overlay with tiles or carpet. In preparation it is typically a somewhat drier mix than wet, poured concrete for foundations upon hard core. On occasion trunking may be inlaid in the screed or under floor heating elements or ducts may be overlaid by a screed.

Sand & Soil 1 5 The term screed' also embraces sand beds for concrete, paving blocks, pool or pond lining installation and soil for grass seeding or turf laying -where considerations of area levelling also apply.

Terminology -Level For convenience of reference herein the term level' is used to embrace either a literal horizontal, to a plumb line or spirit level, or a desired inclination to the horizontal. Other considerations are surface evenness and consistency with a target reference line or plane. Screed levelling implies levelling a plane surface, by reference to mutually orthogonal lines in that plane, for example using boards set at opposite sides.

Wall & Ceiling A wall or ceiling screed generally refers to a plaster or a plaster skim over plasterboard finish. In that context, level' means flat and orientated upright, vertically,horizontally or overhanging.

* . *** I II * I I * I S I I * S I S IS I I II * I S 115 I I I $ S * * I I I S I S I I * S.. S I I Screed & Environmental Condition Inherent screed composition or mix and condition, in particular moisture content, affects working action. Thus an overly dry screed is vulnerable to dragging, tearing and fragmentation -ie crumbling and disintegration -whereas excessive moisture can lead to puddling, that is local surface water pools or puddles.

Similarly, environmental factors including ambient atmospheric conditions, such as temperature and humidity, can affect screed behaviour. With chemical setting accelerators in the screed mix, there may be little time to 1 0 level and tamp down a screed before hardening occurs, that is the screed becomes unworkable.

Tool Requirements A screed working tool should be capable of dealing with a variety of such conditions. Other tool usage factors include aiding work layout and 1 5 measurement.

Screed & Material/Surface Different tools and techniques are needed for different materials and surfaces. Thus, a screed scraping, wiping, dressing or finishing tool should address a surface freely without catching, snagging or dragging material along with it.

A scraper surface is thus desirably of low friction finish and smooth profile, with rounded rather than abrupt angular transitions such as at corner edges. A coating such as a durable baked or chemically hardened paint finish may be applied to promote this. Low friction materials, such as Teflon may be used.

Tool profile should facilitate both a continuous linear stroke and lift action, along with a to-and-f ro' rocking action about a contact edge. Different profile tools are envisaged respectively for floor, wall and ceiling screeds or skims.

Working Angle An optimum working' -ie approach (leading) or departure (trailing) -angle for a scraper blade can be arrived at empirically by: * observation of material removal; and * general handling feel' (eg resistance to pushing or drawing movement); * I *I* I II * I * * I I I I * I I * II I I II * * I III I I I I * * * I I I I I I I I * I.. I * I for a given screed surface and ambient (temperature and humidity) conditions.

Once that angle is struck, it is desirable, but not necessarily easy, to maintain it consistently in a continuous working stroke.

Thus, inadvertent variations, which naturally arise in wrist, arm and shoulder action, will vary material removal rates, and can lead to screed surface irregularities -whose attempted removal can lead to a corrective scraping cycle.

Working angle setting, does not to preclude a push-pull' blade stroke 1 0 action, but is simply to discourage, whatever the immediate intended working angle, involuntary unwarranted erratic blade angle variation.

Optical (Visual) Reference Marking Some aspects of the invention seek to contrive an optical (visual) sighting and alignment reference for setting and preserving an optimum blade 1 5 working angle. The intention is that an operator can discern at a glance a comfortable angle, both in scraper action, ease of working and ergonomic stance -or at least a pragmatic compromise between those factors.

Statement of Invention

According to one aspect of the invention, a screed level tool comprises a bar of wedge-shaped cross-section. This could be extruded from aluminium alloy.

Desirably, a continuous uniform cross-section is adopted. That said, a discontinuous section of different profiles could be contemplated for special purposes. Thus, say, a thicker or fatter wedge could be adopted at the outer margins to bound a thinner or slimmer wedge intermediate section and create a differential boundary scraper action. Diverse combinations and permutations of blade profiles with a common working edge contact line could be adopted. Staggered or offset forms might also be tried. Variant wedge forms could share a common edge, leading or trailing face.

According to another aspect of the invention, a scraper wedge taper' bar or blade could feature surface markings, such as lines, stripes (striations) or bands and/or local differential colouration -so that, viewed from behind the working edge, the blade appearance changes with blade working angle. A striated, banded or gradient tint transition could be employed between opposite blade edges. A form of optical (visual) sighting reference marking is achieved.

* . S.. S ** * . . I * S S I * I * S IS * S IS * S * uS I S S S S * a I I I S I S S I * S.. I S S With a visual reference, on the one hand, erratic involuntary attitude changes become readily apparent and, on the other hand, an intuitive' visual reference is associated with any chosen working blade angle.

Markings could be painted, printed, etched (chemically) or engraved -or a combination of those techniques.

More elaborate optical marking schemes such as interference bands or even holograms might be adopted for precision versions of the tools, such as might be used for scientific or industrial purposes. Such markings might be printed upon plastic films applied as local coatings, wraps or sheaths to tool surfaces.

Optical Interference, Refraction & Diffraction Markings may also be deployed to utilise optical interference, refraction or diffraction effects. To this end, surface irregularities may be used constructively to create viewing patterns or effects -say of light reflected 1 5 from a scraper blade surface contour.

A form of bar code label could be applied to create differential viewing effects. Such techniques could also be applied to ensure equal movement of opposite bar ends -ie a uniform or square scraping movement action.

Preset Angles Visual reference markings for predetermined optimum working angles for various identified screed surfaces could be presented. To avoid undue clutter and visual confusion, these could be juxtaposed in longitudinal segments. Alternatively, a single marking for a common compromise Distinctive Branding Such markings would also afford distinctive branding. Supplementary bespoke markings could be employed to personalise tools, both in ownership and for preferred working angles adopted by a particular user.

Screed Levelling Method According to a further companion aspect of the invention, a method of screed levelling, comprises the steps of: * installing spaced reference bars in or upon a screed bed; * setting the reference bars to a prescribed level * I III I ** * * * I I I I I * I * I *I I I II * I I aIs I I I I I * I I I I I I I I I * II* I I I -both individually and in relation to one another; * resting a scraper blade upon the reference bar; * drawing the blade across the bars -to displace surplus screed material lying above the reference level.

A supplementary step of setting and monitoring the blade angle -say using the optional visual reference markings -might be included, This applies to horizontal surfaces such as floors, but different levelling' techniques are used for ceilings, or upright, overhanging or vertical surfaces such as walls.

1 0 Thus, for, say, wet plaster or plaster board panels with a thin surface skim a scraper is not necessarily appropriate, but rather a rectangular-section, straight bar is used to surface check flatness by surface application and identification of gaps between local contact points. Continuous or intermittent applied pressure, tamping or wiping may be used to even 1 5 surface imperfections.

Modular Kit A modular screed level kit is envisaged, of which principal elements include: * a reference bar -to be set upon then immersed or buried in the screed once levelled (by say an applied spirit level) to set a predetermined reference level at an upper edge; the bar span is sufficient individually, or collectively with others, to encompass the screed; * (push fit / snap action) jointing or connector elements for individual reference bar elements; this allows a boundary consistent to a prescribed level to be set and over which a scraper bar can be run, in mutually orthogonal directions in the levelling plane; * support stakes or pegs with profiled heads to carry and capture a reference bar at wide intervals; opposed stake pairs could be used for bar retention, with underlying saddle or yoke pegs overlaid with a closure hook -the reference bar section captured or embraced therebetween; * a scraper bar, of bespoke tapered, wedge, wiper blade profile -to draw across the screed, while resting upon the reference bar upper edge; to draw ahead of it -and so progressively to one side of the screed -any surplus material lying above that level; the reverse or back side of the bar may be used as a compaction face; * a at. a a.

* a I * a a a a * S a a a, S e at * I I Sit I S I I * * I I a S I I I I S * I.. I * I a support handle with demountable end-mounting clasp or clamp for the scraper bar; the bar is thus held at a prescribed angle to the handle; this assists an operator to keep a consistent, appropriate working angle for the scraper nose against the screed.

* a rectangular profile bar for wall or ceiling plaster or plasterboard skim.

A scraper blade could be held manually, say directly between thumb and forefinger, but for larger spans and a more precise scraping angle, a handle mounting is helpful and convenient for the wide-span, braced sweeping action sought for screed finish.

1 0 Thus a handle or grip helps an operator adopt a more comfortable remote stance, without stooping, to apply significant loads, or rather brace against load reaction, whilst preserving scraper blade stability against sudden slippage and screed damage.

In practice, modularity encompasses different lengths or spans and 1 5 combination or inter-assembly of elements for extension purposes.

Manufacture -Straightening In bar manufacture, such as extrusion, undulations or uneven surface profiles are not uncommon. This undermines levelling using such profiles.

Specially straightened sections are envisaged for reference bars. An adapted opposed roller press is used to draw a bar of otherwise uncertain straightness and re-set it to prescribed standards. Once set, the straightness is generally preserved.

Thus, to quantify the flatness or straightness quotient numerically, a some 1 in 6 departure error can be corrected to nominally some 1 in 300 -representing a hitherto unrecognised precision in manual tools for site reference levelling.

PRIOR ART

Improvisation Improvised screed levels have been contrived from ad hoc scrap material -typically spare lengths of timber -but are of uncertain and so likely inaccurate form, leading to screed levelling errors.

* S *** . S. * p p * * I I I * I * * It I I ** * S I *IS I S I I * * S S * * S S S S I * *5* I S S Standards Construction level standards are not necessarily well specified, but implicit -and so may simply be left to the discretion of a builder or site contractor.

Conformity to paper specifications and consistency are impossible without precision levelling tools.

There have been various past attempts to contrive bespoke screed levelling tools, for greater precision, consistency and ease of working.

Thus, for example

US 5,605,415 Shamblin teaches a screed bar to level concrete in a form, 1 0 with inverted U-bracket fitted to opposite bar ends and with clamp plates set at some 70 degrees to vertical to receive respective pivoted handles, allowing remote access without having to stoop or lean over screed being US2001/034946 Hamdorf teaches a levelling tool with screed bar and 1 5 scraper blade fitted into a slot in the bar; blade insertion depth is variable, with through bolts to set desired levelling height or depth.

US 4,158,937 Wendell teaches an adjustable stirrup for a level reference bar, with threaded stem upstand from a base ferrule and supported cradle or yoke with transverse lock pin.

US2004/0234693 Al Littleton teaches a paired guide tube placed upon screed matric grid.

US D483,632 Masseria teaches a concrete levelling tool of bar with tapered ends and spaced transverse draw tubes.

Embodiments There follows a description of some particular embodiments of the invention, by way of example only, with reference to the accompanying diagrammatic and schematic drawings, in which Figures lA through 1 D show various aspects of a wedge profile scraper blade; More specifically Figure 1A shows local end detail of a removable end fillet; * S ItS a s.

* S S * I I a a * 5 5 *t I a it * I I lit * I I I S * I I I S I I S I S * let I S I Figure 1 B shows a sectional view of an individual scraper blade; Figure 1 C shows a set of scraper blades of different span; Figure 1 D shows a side elevation of manual operation of a scraper blade across the surface of a screed bed; Figures 2A through 2C show various aspects of scraper blade mounting; More specifically Figure 2A shows a 3- D isometric view of a scraper blade with demountable handle clamp; Figure 2B shows a side elevation of a handle-mounted scraper blade in 1 0 use upon a screed surface; Figure 2C shows a group of clamp-mounted scraper blades; Figures 3A through 3C show various aspects of a screed level reference bar and mounting stakes; More specifically 1 5 Figure 3A shows a 3-D isometric view of a reference bar juxtaposed to spaced mounting stakes with yoke cup heads; Figure 3B shows the bar of Figure 3A resting in place on mounting stakes, retained by an overlying hooked capture stake; Figure 3C shows a set of reference bars of diverse spans, (push fit/snap action) bar jointing or connector elements, along with mounting and clamping stakes or pegs; Figures 4A through 4D show various aspects of level reference bar layout and inter-connection; More specifically Figure 4A shows a straight reference bar with juxtaposed, straight, (push-fit/snap action) bar jointing or connector element, ready for fitment for bar extension, as depicted in Figure 4C; Figure 4B shows the bar of Figure 4A with jointing or connector element inserted into a bar end; Figure 4C shows the bar of Figures 4B joined with another as a continuous , , * * * I I I I * I S * It I I II * * * I.e I I I I I * S S S I S I I I S I III * I I straight bar of increased span; Figure 4D shows a bar corner joint with interconnected reference bars; Figure 5 shows a part cut-away view of a scraper blade rested upon spaced level reference bars supported by stakes in a screed bed; Figures 6A through 6D show various aspects of a rectangular section bar; More specifically Figure 6A shows a set of rectangular-section bars of different spans, with face measurement markings; Figure 6B shows a set of rectangular bars without markings; 1 0 Figure 6C shows local end enlargement detail of a marked bar of Figure 6A; Figure 6D shows local end enlargement detail of an unmarked bar of Figure 6B; A fixed-format working head or blade, as adopted in Figures 1 through 6, 1 5 allows a simpler, lower cost, construction -such as by continuous extrusion.

However, more elaborate multi-functional configurations could be adopted which better suit local operating conditions -as reflected in Figures 7A through 7G and 8A through 8G; thus Figures 7A through 7G show variant individual and multiple collective scraper blade configurations; More specifically Figure 7A shows a variable throat taper or wedge profile, with leading and trailing faces relatively movable about (say by live' flex hinge or pivot) a common working edge; Figure 7B shows a dual blade, with lead,rigid, primary blade and trailing, flexible blade; Figure 7C shows a resiliently deformable blade with bottom edge rib initially unloaded and then loaded to trail in action; Figure 7D shows a flat anvil or bolster head blade cluster, allowing a a a a, * * a, , * a, a a d* I a * * * .,a a a * a * I I I I * I a.. a a alternative scraping, smoothing or tamping; Figure 7E shows a multiple spoked blade, with wedge tapered, rectangular, tamper and deformable blade combination -for selective individual presentation by rotary indexing; Figure 7F shows the blade of Figure 7E rotated to an alternative index station; Figure 7G shows a multiple clustered blade, with successive trailing bladelets; Figures 8A through 8G show inter-nested open edge scraper blades; 1 0 More specifically Figure 8A shows a part exploded fragmentary view from one end of internested scraper blades, of complementary, mutually, intertitting sections; Figure 8B shows a side, retracted, elevation of Figure 8A; 1 5 Figure SC shows the blade stack of Figure 8B with a lower blade offset; Figure 8D shows the blade stack of Figure 8C with the lower blade relocated as an end extension; Figure 8E shows an end elevation of stacked inter-nested scraper blades Figure 8F shows a stack of blades in face-to-face abutment to achieve an overall different -in this case quasi-rectangular -form; Figure 8G shows an alternative stacked blade configuration to Figure 8F; Figures 9A through 9H show a wedge scraper blade with optical reference markings to assist determination of blade working angle and provide an immediate intuitive visual indication of involuntary variations in working angle; More specifically Figure 9A shows a scraper blade working face, marked with visual! optical reference Figure 9B shows a blade trailing face, marked with an alternate visual!optical

I

t * , I I t 4 * 4 I 4. I II I I.14 1 -I 4 * I I I I I I I 4 I II 4 4 I reference Figure 9C shows line of sight onto blade with working angle variation.

Figure 9D shows view given line of sight show n in Figure 9C Figure 9E shows blade held at correct working angle, and line of sight onto scraper blade.

Figre 9F shows view of Top Edge of Scraper Blade, indicating ideal working angle.

Figure 9G shows line of sight onto blade with working angle varation.

Figure 9H shows view given line of sight show in Figure 9G Referring to the drawings A modular screed level kit comprises a set of basic elements, namely: * level reference bar 12; * a plurality of setting out or mounting stakes or pegs 13 for the reference bar 12; * a plurality of closure hook stakes or pegs 26 for the reference bar 12; * a scraper bar 10 of wedge shaped profile; * a handle 15 with demountable mounting clamp head 14 for the scraper bar 10; The overall rationale of the kit is to present bespoke tool elements with precise and consistent forms to a screed working surface, with attendant improved levelling precision. This in contrast to the unpredictable and erratic finish achieved with ad hoc scrap timber strips, as are used commonly in the general building trade.

Indeed, the overall standard of straightness is bolstered beyond normal production (say extrusion) standards, by running the blades and reference bars through a specially adapted (counterposed) roller press. This evens out any irregularities such as waviness and imparts a permanent straight set.

? 4 c* 4 444 I Vii * *I I." I * * I 4 VII I I i I I V 4 4 4 4 1 I IIV i Operational Steps * identifying target working area 22; * preparation of underlying bed foundation 23; * bounding target area 22 with spaced support pegs 13 for reference bars 12 * setting desired target level 24 over target area 22 -by laying out reference bars 12 upon pegs 13; * adjusting reference bar 12 levels upon pegs 13, by peg manipulation * overlay of soft screed 20 to embed reference bars 12 1 0 * wiping off surplus screed -by drawing scraper blade 10 across reference bars 12; * allowing screed 20 to settle or set partially or completely; * removing reference bars 12 and support pegs 13; * cleaning and drying all tools; 1 5 With protective paint finishes, no further coating should strictly be necessary, but a light release solvent wipe might be applied between use.

Scraper Blade A hollow, thick-walled, aluminium extrusion with moulded synthetic plastics blanking caps 11 fitted at each end and handed' accordingly.

For the scraper an extruded thick-wall aluminium section provides stiffness and dimensional stability, without undue weight.

A set of different length scraper bladeslO to cover typical screed spans -thus, for example, 1 m, 2m, 3m, assembled up to a combined 6m span might be included Wedge Profile -Included, Approach + Departure Angles An assymetrical right-angled hollow, triangular-profile, section, with rounded radiussed cornersl6A-C and bull-nose 17 to radius 16C with instep 18 to plastic end fitting inserts 11.

A short scraper blade 10 of (say 0.5m) span can be handled manually -as * * I** S ** * . S S I I S I S I * I IS I I IS * S I Ill * I I I S a a a a S I I I I I * IIS S S S depicted in Figure 1 D. Longer spans (of say 1.5m upwards) are more readily controlled with a handle mounting as depicted in Figures 2A through 2C.

A handle mount 19 with a clamp head 14 (set with some 45 degree angle to the handle stem or shank) and aligned mounting apertures 29 in opposite faces for through clamping bolts 30.

Support stakes or pegs 13 with yoke cup heads 25 are employed; along with optional retention or clamp stakes 26 with hook head 27. A round reference bar 12 profile fits and is retained securely therebetween.

1 0 Given a stable screed bed 20, a yoke head peg or stake 13 could be omitted in favour of reliance upon an open-face saddle peg or stake.

Rectangular Profile A rectangular profile bar 21 could serve for tamping (ie with direct surface pressure) or wiping when drawn flat over a screed surface.

1 5 Although envisaged primarily as a discrete element in an overall screed levelling kit, a combination or multi-role bar and blade could be contrived -say with a wedge scraper as an add-on or adjunct to the trailing edge of an otherwise flat bar.

Alternatively, a clustered wedge -specifically stacked opposed wedge profiles could be assembled to create a rectangular overall form - as in Figure 8F.

Visual Reference of Blade Angle As an example of a visual reference marking, a diagonal stripe or banded marking is employed on the rear edge to create a contrast with the side faces.

A tapered or waisted -or other varying width -band or stripe profile could be used to exaggerate operator perception of different blade angles or dispositions in relation to a given viewing angle -viewed from a rear edge opposite the working edge. Indeed changing the blade angle would have a similar effect to changing the viewing angle.

A spiral blade tape wrap could be of even or varying pitch, to promote the visual differences at different blade set angles.

Aside from a continuous tape, multiple discrete tape segments could be deployed. Some or all of these could be of waisted taper longitudinally. A co-operative juxtaposition of tape profiles could be laid out with differential * I ItI I ** * I I * I * I I * I I I II I I II * I * III I I I I I * I I I I I I * I I * III I I I spacing. Different colour and/or pattern tape segments could be used.

Similarly, a stripe could run from the scraper blade working edge and up over one face, across the rear edge, to the opposite face.

Thus, viewed from an operator standpoint, at the rear of a scraper blade, various scenarios include * neither side face apparent; * one or other side faces apparent; * both side faces apparent to the same or different degrees; The view reflects the proximity of the blade to the viewer. Thus, using a 1 0 remote handle mounting, a viewer is set back and is unlikely to see both faces simultaneously, but rather one or other face to a varying extent.

By colouring the faces differently, a prominent visual indication is given of a trailing (wiper) or leading (shovel) blade action.

Carry Wrap 1 5 A bespoke profile portable carry bag or wrap (not shown), slung with a shoulder strap, can be used to protect tools in storage and carriage.

Resilient clips or ties can be used between otherwise loose tools to inhibit mutual chafing.

Rigour As with all surface working, rigour in careful, methodical layout and marking-out is important to preface tool action. That is, however precise individual tool profiles are crafted, unless level reference bars are set correctly, the screed will not be correct.

The bespoke reference bars, support and clamp stakes allow rapid setting out to high standards.

Spirit Levels It is envisaged that discrete independent proprietary spirit levels -ie separate from the bars -would be employed for bar levelling. Consideration has been given to the option of integrated spirit levels within the bars, but it is felt that these would be vulnerable to damage -particularly upon impact tamping to set prescribed levels.

* * *.. S * I * * S I * I * I I * ** S S It * I I *ts S I I S S * S * S * S I I I S * us I I S Variants -some illustrated Stacked, clustered or variable profile scraper blades (not shown) could be contrived to vary the leading and traHing face angles and the included angle between those faces.

Variable Wedge A variable -ie expanding or contracting -wedge blade and an adjustable setting angle through a handle mounting clamp are also envisaged -as reflected in Figure 7A.

Multiple Blade 1 0 A multiple blade scraper, with rotary indexing to present a desired blade into surface contact is also envisaged -as reflected in Figures 7E and 7F.

One such blade could be a horizontal smoothing trowel.

A blade clamp (not shown) could feature a male-female throat interf it, with a multiple blade end, say configured as a star section with radial webs, spokesorlimbs.

Flexible Blade Flexible or resiliently deformable blades -such as of synthetic plastics -might be used to achieve a cushioned wiper action, as reflected in the single blade of Figure 7C and the trailing secondary blade of Figure 7B.

Sequential + Stepped Offset Blades Multiple sequential blades -such as the rigid primary blade and flexible secondary blade of Figure 7B -could provide both an initial preparatory and follow-on finishing wipe action. These could be mutually offset in depth and spacing. Internesting Bars Hollow internesting sections of complementary profile

could be adopted for different scraper bar spans -as reflected in Figure 8A-8D. This would allow compact storage within a common outer profile. It would also bulk up the internested mass, for greater inertia and stability -albeit with modest working (drag or draw) load penalty.

Resilient Wiper A wiper edge blade, rib or lip of say resilient synthetic plastics could be inset into the section ends to allow mutual blade wiping and cleaning upon * * .s* . I. * * * I I 8 I I * I I I II I I II * I I III I I I I I * I I I I I I * I 8 * III I I I insertion. This could also impart a snug cushioned or damped interf it, with modest friction to inhibit inadvertent separation.

Smaller scraper bar sections would be easier to handle directly for shorter spans. Their scraping or wiping performance need not be significantly different from longer bars with larger sections -given a common cross-section proportion and operating angles.

Material Materials adopted for scraper and level bars are a compromise between weight and hardness to minimise wear and accumulated inaccuracy through 1 0 use. They should also be corrosion-resistant for longevity outdoors.

Aluminium alloys are a reasonable economic materials choice.

Mounting Pegs Mounting pegs 13 with saddle profile heads 25 to receive a reference bar profile could be provided for soft screed to obviate sinking. Conversely, 1 5 extraction pegs 26 with hook profile heads 27 can be used to extract and retrieve embedded mounting pegs.

These could be stored temporarily within the hollow scraper bar section, in which case readily removable end closure caps, such as resiliently deformable plastics bungs, would be fitted.

* 1 9ff 9 9? D( * * . , . , * 0 4 I * .9 * I ft * 1 I t** I 0 I I 9 * I I I S * I I I I a Iq* V * S Component List 1 0 wedge section scraper blade 11 endcap 1 2 level reference bar 1 3 mounting stakes/pegs 1 4 mounting clamp handle 1 6 radius corners 17 bull nose 18 instep edge 1 9 handle mount screed 21 rectangular section bar 22 target area 1 5 23 bed foundation 24 target level yoke cup 26 clamp/extraction stake/peg 27 hook head 28 joining or connector element 29 mounting aperture clamping bolt 31 horizontal smoothing trowel 32 trailing face 33 top edge 34 optiumum working angle working face 36 line of sight onto scraper blade

Claims

t. ., a $ a I a I I a * a * * ta a ft * a a *.i I * a a a * a a a a a I

* * aaa a a Claims A scraper bar (10) such as for screed levelling, comprising a (hollow) tapered or wedge profile section with a rounded or bull nose working edge (17), for screed contact.
2.

A scraper bar of Claim 1, with a right-angled triangle section, between one trailing face (32) and a top edge (33).
3.

A scraper bar of either preceding claim, of thick-walled, hollow aluminium section.
4.

1 5 A scraper bar of any preceding claim, with an operator manual handle (15) fitted to a demountable bar clamp (29), configured to present the bar (10) at a desired (optimum) working angle (90) to a screed (20), when held at around waist level.
5.

A scraper bar or blade of any preceding claim, incorporating visual reference markings for blade angle alignment.
6.

A scraper bar substantially as hereinbefore described with reference to and as shown in the accompanying drawings.
7.

A scraper bar of Claim 1 manufactured or re-worked by passage through an opposed roller press to produce straightness precision of 1 in 300 or better.

* 1 1,4 4 4 4 I, 4, I I I I II 4 4 I * I I ** I I P 4 4 * p 0 * I I -P III 4
8.

A modular screed levelling kit comprising; a wedge shaped scraper bar of Claim 1, plurality of reference bars, along with bar support pegs.
9.

A modular screed levelling kit of Claim 8 incorporating rectangular section bars
10.

1 0 A modular screed levelling kit of Claim 8 incorporating joining or connector elements.
11.

A method of screed levelling, using scree levelling kit as described, 1 5 and comprising the steps set out herein.