GB2192418A - Screeding machine - Google Patents

Abstract

A screeding machine, operated by a rough terrain fork lift or other tractive machine, for levelling and variably compacting sand and other granular materials, comprises two or more screeder beams (12, 13) or other levelling and/or compacting means parallel to each other and joined by one or more cross members (14). <IMAGE>

Description

SPECIFICATION Screeding machine This invention relates specifically to a machine for screeding (or levelling and partially compacting) a layer or bed of sand upon which paving blocks are laid. The machine is however suitable for levelling and partially compacting other materials or other granular mixtures for other purposes.

A sand layer is used as a bed for paving blocks. This layer should be only partially compacted for two reasons: a) paving blocks vary in thickness as a result of the manufacturing process employed and b) the joints between paving blocks should be filled with sand. When paving blocks, which have been laid upon a partially compacted layer of sand, are vibrated or compacted using a vibrating plate the upper surfaces of the blocks are levelled and sand is. forced up into the lower part of the joints. Dried sand is then brushed or otherwise applied to the surface and the vibrating plate is used a second time to completely- fill the joints with sand and to further bed-in the paving blocks.

The normal method to prepare this layer of sand is as follows: Strips of wood or lengths of steel are set at the required level (hence the dictionary definition of a screed) Sand is spread to roughly this level by hand.

A plank or beam, which spans two screeds and which is commonly called a screeding board or a screeding beam, is drawn by hand along the screeds to level the sand. A sideways sawing motion is often used to spread the sand sideways to fill low areas.

When too much sand builds up in front of the screeding board the effort required to draw it forward becomes too great. Some of thins build up of sand has to be moved by shoveling or by lifting the screeding board so that part of this build up can be drawn forward.

Screeding beams fitted with power operated vibrators, which are commonly called tamping boards, are used to level and compact concrete and other mixes or materials which are sufficiently wet to flow'or move under the board. Trials were carried out with powered tamping boards to level and partially compact sand but satisfactory results were not achieved. The sand was not spread or levelled before the high areas were compacted, leaving low areas or poorly compacted sand. There sulting paved area was unsatisfactory with low areas and with high areas where the blocks were not bedded-in.

According to the present invention there is provided-a -screeder beam assembly comprising two or more screeder beams or other levelling and/or compacting means mutually located and spaced one in front of each other by a cross member of by cross members or by other means. There may also be provided suspension and/or traction link points or mounting brackets or other means on the screeder beam assembly such that the screeder beam assembly may be drawn or pulled over the material to be levelled and partly compacted and such that the screeder beam assembly may be lowered or raised.

The desired level may be achieved by drawing the screeder beam assembly over screed strips or bars, hereafter referred to as screed rails, or there may be provided other means of level control. There may be provided adjustable but inert level following devices for use when there is a kerb or paved area or other datum level parallel to the plane of the desired screed level and adjoining of near to the one or more sides of the area to be screeded. There may also be provided active level following devices or means whereby the screeder beam assembly may be maintained at the desired screed level, or may be pre-vented from descending below the desired screed level, as if the screeder beam assembly were being operated on screed rails.

According to the present invention there may be provided means of increasing the width of the screeder beam assembly, i.e. the length of the screeder beams. There may be provided extension screeder beams or extension screeder beam assemblies which may be secured to the basic screeder beams or to the basic screeder beam assembly. These additional beams or beam assemblies may be extending, i.e. enabling the screeder width to be incrementally extended, and/or may be extensions, i.e. increasing the length of the beam or beam assemblies to which they are attached by a fixed amount.

According to the present invention there may also'be provided means to achieve a cambered screed or surface wherein this- may be achieved by providing curved screeder beams and/or curved edges for the screeder beams and/or this may be achieved by one or more angular changes of the lower edge of a combination screeder beam at the points where the component or part beams are secured to each other to form the combination screeder beam, or by other means.

According to the present invention there may also be provided rakes or tines or other means to loosen material which has been heavily compacted, and means to locate. or secure these rakes or tines to the screeder beam assembly.

According to the present invention theremay be provided means of conveying excess material which builds up, or'tends to build up, in front of a screeder beam to either or both ends of the screeder beam, which means may include drawing the screeder at an inclined angle to the direction of screeding'and/or power operated augers or dther conveying de -vices or device located or mounted in front of the-screeder beam.

According to the present invention there may also be provided the means to produce a screeded layer which consists of a top layer of even, or nearly even, thicknes that is lightly compacted and which consists of a lower layer of screeded material that is heavily, or more heavily compacted, the thickness of the lower layer varying when or ifthe level of the sub-baseupon-which the material is to be screeded varies relative to the required screed level;This may be achieved by producing a heavily compacted layer of material to roughly the required screed level and by providing a rake or rakes or row of tines mounted adjus -tably in front of the rearmost screeder beam, or other means to loosen the upper part of the heavily compacted layer of material, and by providing a rearmost screeder beam which screeds and lightly compacts this upper layer.

To achieve varing degrees of compaction, there may be provided according to the pre sent invention means of adjusting the angle of the lower face of a screeder beam relative to - the direction of travel so that the lower front edge can be set either higher or lower than the-lower rear edge of the screeder beam, and/or there may be provided beams with rounded or chamfered lower corners on one face-and there may be provided means of re versing the-beame and or the screeder beam assembly so that alternative faces of the beam or beams may-be-used ànd/or there may be provided other compacting devices such as rollers or vibrating plates, According to the present invention there may be provided a means of connecting the screeder beam assembly to a tractive machine such as a rough terrain fork lift, a loading shovel, a dumper truck, an agricultural tractor or any vehicle or machine that is sufficiently heavy and powerful to enable it to draw or pull the screeder beam assembly over a roughly spread sand, or other material, which is- to be screeded (i.e., levelled and partly compacted). When the tractive machine does not have lifting and tilting facilities, or when such facilities are unsuitable, there may be provided power operated lifting and tilting fa cilities. There may be provided a suspension and traction frame with mounting clamps or brackets or other means for attaching the frame- to the tractive vehicle and with suspen sion and traction link points or brackets, and there- may be provided suspension and trac tion link points and brackets on the screeder bearn-assembly, and there -may be provided chains or other means to link the link points on the screeder beam assemblyto those on the-suspension and traction frame, or to otherwise link the screeder -beam -assembly to the'tractive machine, the geometry or arrange ment of these links and their linking points being such the screeder bearri- assembly may be operated in three modes, namely: (one) suspended clear of the ground, (two) with the weight of the screeder beam assembly acting on the material being screeded and/or acting on the screed rails or on the other means of level control being employed, and with the suspension links slack and the traction links'horizontal, or nearly horizontal, and under load, with the tractive machine drawing the screeder beam along behind it (the purely tractive mode), (three) the weight transfer tractive mode in which the tractive links are not horizontal and therefore impose an upward or downward component of force of the screeder beam assembly and/or in which some or all suspension links impose an inclined upward force on the screeder beam assembly and/or in which a downward force is imposed on part of the screeder beam assembly.

According to the present invention there rnay also be provided angled scraper blades and suitable mounting brackets for mounting the scraper blades on the tractive machine in front of its driven wheels so that all but a small depth of the roughly spread material is cleared from the path of the driven wheels when the tractive machine is drawing the screeder beam assembly, or there may be provided other means of preventing wheel slip Specific embodiments of the invention will now bye described by way of example with reference to the accompanying drawings in which: Figure 1 shows in projection a screeding machine being drawn in mode (two) by a rough terrain fork lift schematically indicated by its forks and wheels drawn in dashed lines.

Figure 2 shows in plan a screeder beam assembly fitted with extending beam assem -blies and shows how the traction linkage allows the screeder beam assembly to follow a kerb or swing back if it comes into contact with an obstruction.

Figures 3, 4, 5, and 6 show in side elevation, or side section, how the screeding characteristics of a two beam screeder may be varied.

Figure 7 shows in plan a screeder equipped with active level control devices and an excess material conveying device and operating at an~inclined angle.

Figure 8 shows in front elevation details of a screeder beam.

Figure 9 shows in side elevation or section details of means of locating and clamping extending screeder beams.

Referring to Fig. 1 there is provided a suspension and traction frame 1 which consists of a front cross member 2 and a rear cross member 3, a left side member 4 and a right side member -5, traction link mounting points or brackets 6- and 7, left side suspension link mounting points or brackets 8 and 10 and right side suspension link mounting points or brackets 9 and 11 which are just visible. The suspension and traction frame, in this example, is attached to the forks of a rough terrain fork lift truck by clamps which are not drawn and which clamp to the cross members 2 and 3. The suspension and traction frame side member 4 and 5 are tilted downwards at the front so that the traction link mounting points 6 and 7 may be operated close to the ground and are fitted with angled front end plates or skid plates so that they will not dig into the ground or sub-base.

The screeder beam assembly in this example consists of a one piece front screeder beam 12, a similar rear screeder beam 13, a left side beam cross member 14, a right side beam cross member 15 and combined suspension and traction link points or brackets 16 and 17 and similar brackets 18 and 19 which as drawn serve-as suspension link points. It should be noted that the screeder beam assembly could be rotated 180O about a vertical axis and could then be operated in reyerse to its normal direction.

There are in this example provided traction chains 20 and 21 and suspension chains 22, 24 and 25 which are drawn and a right side front suspension chain 23 which is not drawn but which similarly serves as a link between brackets 9 and 17. Note that right side traction chain 21 is drawn attached to the upper.

most point or mounting hole on bracket 17 to illustrate one way in which the screeders operating characteristics can be-altered or tuned.

Note also that the screeder is drawn in Fig. 1 operating in mode (2) with the traction chains 20 and 21 tight and approximately horizontal and with the suspension chains slack and that the screeder is being drawn forward by definition in the direction of the arrow 100 regardless of whether this direction would be regarded as forward or reverse for the type of tractive machine being employed. In this example, the driver of the schematically represented as a rough terrain fork lift would select "reverse" gear to draw the screeder forward.

According to the present invention there may also be provided a suspension and traction system for the screeder beam assembly wherein the beams will deflect away from an obstruction in both the raised mode and when it is screeding, and-wherein the ends of the screeder beam will deflect round and tend to follow a kerb or other obstruction that is marginally within its normal path or effective screeding area. This is achieved in this example by positioning the 'screeder beam linkage points wider than the suspension and traction frame linkage points. There may also be provided overload trips or shear pints in the traction links or in their mountings or other means of damage prevention may be provided.

Referring to Fig. 2, which shows in plan a screeder beam assembly and a tractive machine represented schematically by its wheels 26, 27, 28 and 29, the traction chains 20 and 21 are shown as dashed lines between link points 6 & 16 and 7 & 17 respectively. In this embodiment of the invention there is provided a basic screeder beam assembly consisting of beams 12 and 13 and beam cross members 14, 30, 31 and 15 and there is provided a left side extending extension beam assembly consisting of beams 32 and 34-and an extension cross member 36 and a similar right side extending beam assembly consisting of beams 33 and 35 and cross member 37 and there is provided, but not drawn, a suspension and traction frame 1 and suspension link system as shown in Fig. 1.If the left outer end 101 of the front screeder beam 32 comes up against an obstruction or into contact with a kerb as indicated by the curved line 102, the entire screeder beam assembly will swing to the right. The traction link points 16 and 17 will follow the loci represented by dashed line arrows 106 and 107 respectively, relative to the tractive machine. Similarly, the left outer end of the extending beam 101 will follow the locus 103, relative to the traction machine, until it clears the obstruction or as it follows the kerb 102. If the screeder beam 32 comes into contact with obstructions at points 108 or 109, these points on the beam will follow the loci represented by arrows 104 and 105 respectively, relative to the traction machine, or will follow a more rearward direction if the traction chain 21 becomes slack.

Fig. 3 shows one means by which a slightly compacted level surface may be achieved. -The front 12 and rear'13 screeder beams are provided with sharp lower corners and with means to adjust their inclination relative to the beam cross members. When the lower front corner or screeding edge is lower the rear corner, the excess material is cut or sheared or ploughed off. The weight of the screeder beam assembly is carried mostly- by the screed rails or the alternative level following device being employed. The line 110 represents the upper surface of the screed rail or the desired screed level.If or when a large ammount of material has built up in front of the beams, the suspension and traction frame 1, Fig. 1 may be raised so that the screeder beam assembly is operated in mode (three) and the excess material drawn forward with the beams operating slightly clear of the level 101 and with the weight of the beam assembly carried mostly on the suspension and traction links. The screeder can be lifted clear, reversed, lowered and agairr drawn forward in mode (two) to remove the remaining excess material.

Fig. 4 illustrates one means by which greater degree of compaction may be achieved. ln this example the screeding edges are sharp corners and the beam inclination is level, i.e. the lower faces are in the same plane. When the screeder is drawn over the roughly spread material for a first "pass", it is operated in mode (three) with the front beam raised. The lower faces of the beams, because of the inclination, press down on and compact the material. More than one pass may be required. Alternatively, the beam inclination may be adjusted to raise the front cornerds relative to the rear corners and/or greater weight may be applied to the beams by the addition of beam weights or transfer of suspension and traction frame and fork lift carriage weight.

Fig; 5 illustrates another means by which a greater-degree of compaction. In this example both screeder beams have a lower corner or edge which is rounded and which is on the front of the screeder beams. Alternatively there could be provided a chamfered corner or corners or an inclined lower face or faces or other means to achieve the same effect. Note that the screeder beam assembly as illustrated in Fig. 5, when reversed or operated in the opposite direction would compact the material being levelled to a lesser degree.

Fig. 6 illustrates, by way example, a screeder be-am assembly that produces a screeded layer which consists of a top layer of even, or riearly even, thickness that is lightly compacted and which consists of a lower layer- that is heavily, or more heavily, compacted. There is provided a front screeder beam 12; a rear screeder beam 13 and a rake or a row or row of tines-38, or otherdevice to loosen a layer of material, mounted adjustably in front df and close to the- rear screeder beam 13.The material passing under the front beam is compacted heavily to form a layer with an upper surface at, or nearly at, the level 110, the heavy compaction being achieved by the shape of the front screeder beam and/or by- the weight of the front screeder beam bearing- on the material below it and/or by-a downward force exerted upon the front screeder beam by the traction linkage pulling in a downward direction and/or by weight transfer from the rear of the screeder beam assembly and/or by the provision of additional weights above or in front of the front screeder beam and/or by other means which include the provision of vibrating plates behind the front screeder beam as indicated by 39 in Fig. 6.The layer of material loosened by the rake 38 is levelled by the rear screeder beam but only lightly compacted because of the shape and attitude of this beam and because its weight is carried mostly by the screed bars of rails or by the level following device or devices as are being employed and/or is carried by weight transfer to the front screeder beam.

Fig. 7 illustrates, by way of example, a screeder beam assembly being operated at an inclined angle to the direction of forward tra vel 100. A simple screeder beam assembly, basically similar to that illustrated in Fig. 1 may be operated in this manner, the angle of inclination being such that excess material in front of the screeder beams is diverted or "ploughed" off to the side. This example is.

however provided with a material conveying device in front of the front screeder beam 12 and is provided with active level following de vices.

The active level following devices illustrated in Fig. 7, by way of example, consist of wheel assemblies 40, 41, 42 and 43, which are provided with thin wheels which cut through the sand and run on the sub-base thereby carrying the weight of the beam as sembly and with power operated lifting de vices which raise or lower the screeder as sembly relative to the wheels and thus the sub-base, a level control unit or level control units which monitor the level of the screeder beam assembly relative to a datum level and which transmit level correction signals-to the power operated lifting devices and which may also provide control situation signals such as "variation of screeder beam level(s) relative to datum level within set limits" and/or "screeder beam level(s) exceed set high alarm limit above datum level" and/or "screeder beam level(s) exceed set low alarm limit below datum level", and consists of a datum level device or devices such as a laser or other light beam projected in a plane parallel to the plane of the required level.

In the example illustrated in Fig. 7 the wheel assemblies are also provided with a castoring or swiveling capacity and may be provided with a swivel locking or a steering device to control, or to assist in the control of, the attitude of the screeder beam assembly rela tive to the tractive machine. The attitude of the screeder beam assembly may also be con trolled by the geometry of the traction links.

In Fig. 7 there is provided a short traction link -45 and longer traction link 44 which may be provided with power operated length adjust ment, - such that when the side thrust on the inclined screeder beams and on the material conveyor increases and therefore moves the screeder beam assembly to the right side, the angle of the short traction link 45 to the for ward direction of travel 100 is increased and thereby balances the increased side thrust with little change in the inclination and si deways movement of the screeder beam as sembly.

The conveying device, py way of example, consists of a three section auger flight 46 mounted on adjustable bearing brackets 47, 48, 49 and 50 in front of the front screeder beam 12 and rotated by a geared hydraulic motor or other means.

There are also provided traction link points or pivots 62 and 63 mounted on a suspen sion and traction frame or mounted on the tractive machine and means for lifting the screeder beam assembly. Some or all of the screeder beam weight may also be transferred by active level control lifting devices to the tractive machine.

Fig. 8, by way of example shows some screeder beam details. There may be provided an extension beam joint which consists of hinge plates 52 and 53, a hinge and joining pin 54 a camber adjusting threaded bar and nut assembly 55 or other means of securing and adjusting the camber angle of extension beams. There may also be provided a kerb skid plate 56 and kerb skid bracket 57 which may be adjustably clamped or otherwise attached to mounting member 58 or other means to control the -screeder beam height relative to a kerb 59 or other surface. There may also be provided an adjustably mounted rubbing member 60 on the end of a screeder beam.

Fig. 9, by way of example shows details of the screeder shown in Fig. 2. There may be provided clamp assemblies, two of which 61 and 62 are shown clamping or securing left side extending screeder beams 32 and 34 to the main screeder beams 12 and 13 respectively, and there may be provided means of alignment or location as drawn or by other means. Alternative clamping means may be provided, included power actuated,' bver-centre or toggle action or eccentric mechanisms. Extensions may be provided to further extend either the main or the extending screeder beams.

Claims (13)

CLAIMS -

1. A screeding machine for levelling and partly compacting sand or other materials or other granular mixtures comprising a screeder beam assembly corisisting of two or more screeder beams or other levelling and/or compacting means mutually located and spaced one in front of each other by a cross member or by cross members or by other means.

2. A screeding machine as claimed in Claim 1 wherein linkage mounting points are provided on the screeder beam assembly and are provided on a tractive machine and wherein links between these linkage mounting points to enable the tractive machine to raise and lower the screeder beam assembly and to enable the tractive machine to draw the screeder beam assembly over the material to be screeded or levelled and partly compacted, the desired level being achieved by screed strips or screed rails or other means of level control.

3. A screeding machine- as claimed in any of the above Claims wherein there may be provided power operated lifting and/or tilting means when these are not provided by the tractive machine or when the lifting and/or tilting means provided by the tractive machine are not sufficient.

4. A screeding machine as claimed in any of the above Claims wherein there is provided a suspension and traction frame consisting of a frame with suspension and traction link mounting points or brackets and mounting brackets or other means of attaching the frame to the tractive machine and where in there is provided chains or other means of linking the screeder beam assembly to the suspension and traction frame.

5. A screeding machine as claimed in any of the above Claims wherein the screeder beam assembly may be raised and lowered by the tractive machine and may be drawn over the material to be screeded with the weight of the screeder beam being carried by the material and/or by the screed rails or other means of level control and/or may be drawn over the material to be screeded with the weight of the screeder beam assembly partly carried by the tractive machine and/or increased by a downward load applied by the suspension and traction frame or by the tractive machine.

6. A screeding machine as claimed in any of the above Claims wherein different upward or downward loads may be simultaneously applied to the front and to the rear of the screeder beam assembly.

7. A screeding machine as claimed in any of the above Claims wherein the arrangement and dimensions of the suspension and traction links or other means of suspension and traction is such that when an outer part of the screeder beam assembly is drawn against an obstruction the screeder beam assembly deflects from its normal path and/or is such that the end of the screeder beam assembly tends to follow a kerb or other obstruction that is marginally within its normal path.

8. A screeding machine as claimed in any of the above Claims wherein there is provided means for the screeder beam to deflect or move relative to the tractive machine when any part of the screeder beam assembly is brought into contact with an obstruction.

9. A screeding machine as claimed in any of the above Claims wherein the width or effective working width of the screeder may be increased or reduced by altering the length of the screeder beams or other levelling and compacting devices or by altering the inclination of the screeder beams or other levelling and compacting devices relative to the direction of travel.

10. A screeding machine as claimed in any of the above Claims wherein there is provided sliding or extending extension beams or beam assemblies and there is provided location and clamping or other means to adjust and or secure these extensions and/or wherein there may be provided extension beams or beam assemblies and suitable attachment means to thereby extend the main or basic screeder beams or to extend the sliding or extending extension screeder beam or beam assemblies.

11. A screeding machine as claimed in any of the above Claims wherein the degree of compaction achieved may be varied or changed or altered by varying the method of operation or by adjustment of the location of inclination of one or more screeder beams relative to the other beam or beams or leveling or compacting devices or by reversing the screeder beam assembly relative to the tractive vehicle or by reversing individual screeder beams relative to the other beams or to the screeder beam-assembly or by altering or changing the screeding edge or corner of any screeder beam or by any other means.

12. A screeding machine as claimed in any of the above Claims wherein there may be provided means of conveying excess material to one side of the screeder beam assembly and/or of spreading or conveying roughly spread material across the screeder beam assembly.

13. A screeding machine substantially as described herein with reference to Figs. 1-9 of the accompanying drawings.