GB2180285A - Self advancing lifting toe support for underground longwall working - Google Patents

Abstract

The supporting unit has two base units 10 between which a beam 25 is arranged to which the longwall conveyor 18 is attached. The unit has means for lifting the two base units 10 with respect to the beam 25 and a hydraulic cylinder 20 acting between the base units 10 and the beam 25 for advancing the two base units 10 towards the longwall (i.e. to the left as shown in the drawing) while the beam 25 engages the ground. The lifting means can be a separate hydraulic cylinder or a bell crank 38 that is attached by a central pivot 30 to the two base units (10) and by a further pivot at one end of the crank to hydraulic cylinder (20). The second end of the bell crank (38) is fitted with a roller (28) that moves over the beam (25) when the base units (10) are being advanced. Once the two base units (10) have been advanced and contact the ground again, the hydraulic cylinder (20) is retracted to advance the beam (25) and the conveyor (18) towards the longwall (i.e. to the left). <IMAGE>

Description

SPECIFICATION Supportinurift.frra mechanized su,oportfor under- ground'[ongwafrworking The invention relatestoa.supporting unitfor underground longwallworkin'g.fo.r a mechanized: support. The proposed supporting unit can be prefer ably used in places, where the strength of the bottom wali is slight, orjust plastic or it swellsnunderthe influence of water.

In course of underground mining, i.e. longwall working, mechanized supporting devices are well known, which consist of interconnected supporting units arranged next to one another. A subbase, a cap-piece, an interconnecting articulated rod, a hyd raulic prop inserted between subbase and cap-piece, as well as a hydraulic pushing cylinder performing forwards movement-which is connected at one end indirectly to the conveyor lying along the longwall underwork- belong to the supporting unit each.

Known supporting units generally differ in respect to the individual formation ofthe aforementioned structural parts or e.g. to the formal design of the articulated rod, the number and specificfeature of the hydraulic props.

The cap-pieces of the known and generally used supporting units are extending to a considerable extent at the end ofthe subbase facing the frontal face of the longwall, with the purpose two be able to support the section ofthe longwall having been left unsupported in course of breaking in the possibly quickest manner. In case of a projecting cap-piece, when receiving the load, the end of the subbase facing the frontal face ofthe longwall transfers a far larger load to the rock ofthe bottom wall, then the end ofthe subbase facing the break. This circumstance is considered as most disadvantageous, in particular, if the bottom wall is of low strength, it consists of a plastic material or swells in the presence of water.Under disadvantageous circumstances it means that as a consequence ofthe concentrated load affecting the end ofthe subbase, the end ofthe subbase sinks into the bottom wall. Accordingly, when the supporting unit is advancing forward, the subbase stops and the subbase can be lifted only by special measures, thereafter the supporting unit isto be moved forward.

In orderto avoid at least partly the outlined detrimentous circumstances, with certain known supporting units the subbase has been lengthened towards the frontal part of the longwall. The end of the subbase having been lengthened in such a mannenapproached the projection ofthe end of the cappiece related to the plane of the bottom wall, as a consequence, concentrated load at the end. ofthe subbase ceased.However, the drawback. ofsa id solution lies in th at-- as th e subbase cauld be lengthened below theconveyor only-the conveyor had to be liftedto an extent being in compliancewfth the thickness ofthe subbase Atthe same time the conveyorthus lifted reduces the efficiency of stacking the brocken rnck Afurther disadvantageous feature lies in that the heightened ed subbase cannot easily follow the unevenness of the bottom wall, accordingly, a far larger intermediate section is needed for overbridging the unevennesses,than with supporting units having shorter subbases.

With afurtherversion ofthe known solutions, itwas tried to prevent sinking of the subbase ofthe supporting unit in such a mannerthat instead of lengthening the subbase it was composed of two longitudinal elements: accordingly load was distri buted to these two beamlike elements ofthe subbase.

Steadying is carried out by means of hydraulic props with two-way action. With such a sol utiQn-- when the subbase sunk-the following measures were taken: bythe aid of one ofthe hydraulic props with two-way action one ofthe elements ofthe subbase was lifted, meanwhile by the aid ofthe other subbase element belonging to the supporting unit and by means of the co-operating prop the cap-piece was kept in a spanned state. The subbase element thus lifted was bedded to the necessary extent and repeatedly spanned with the belonging prop. The same process was carried out with the other subbase element. The supporting unit with the subbase thus lifted could be moved forward.

Shifting ofthe supporting unit with the outlined construction requires a considerable expenditure of labour, in addition material requirement is also high.

As a matter of fact, said solution could not solve completely undisturbed moving of the supporting units.

A flu rther disadvantage of said structural design lies in thatthe bearing surface ofthe elements forming the subbase is smaller, than that of the undivided subbase elements, as the bearing pressure affecting them increases.

The aim of the invention was to eliminate mostly the drawbacks and deficiencies of the known supporting units and to develop a supporting unit which enables undisturbedshifting ofthe supporting unit with bottom walls of low strength with rocks tending to swelling when soaked with water.

Afurtheraimoftheinventionwastoomitlengthening ofthe subbase and thus lifting of the conveyor should become superfluous.

Afurther aim was that spanning between the subbase and the cap-piece could be realized with simpler and cheaper one-way acting props, in addition, shifting forward of the supporting unit according to the invention should not require more live labour, than unavoidably necessary, material requirement could be reduced, expenditure oftimeshould not exceed the necessary expenditure, being usualwith bottomwalls of good quality.

In accordance with the invention, with this novel supporting unit the aim set will be achieved so, that the subbase is formed of a subbase element and a beam to be guided and rotated in relation thereto, with which the part ofthe bottom beam facing the frontal face is connected articulated to the conveyor, furtheron, the supporting unit according to the invention is provided with an elevator, which is connected partly to the subbase element, partly to the bottom beam, while the pushing cylinderforforward shifting is connected with one end to the aforementioned lifting means orthe subbase element, whereas the other end is connected to the bottom beam.

With a preferred embodiment ofthe supporting unit ofthe invention the subbase is formed oftwo symmetrically arranged subbase elements and the bottom beam is lying inbetween. Expediently the construction is formed so, that an open duct enclosed bythe subbase elements should receive the bottom beam, in which the bottom beam is restricted in respectto its vertical motion upwards. This restriction will be achieved by the ribs belonging to the subbase elements and protruding into the duct.

In a plurality of cases it may be advantageous, if the partofthe bottom beam being in an articulated connection with the conveyor incorporates the part of the bottom beam facing the conveyor. With this solutions, as a matter offact, the bottom beam consists of two parts which can be interconnected with a hinge.

The lifting device-which is also connected between the bottom beam and the subbase element guiding the bottom beam-may be constructed in several ways. A construction is considered as the most simple one, with which the lifting device has essentially a bell crank lever andthe bell crank lever is bedded in relation to the subbase element. The end of the arm is advantageously bearing up againstthe bottom beam via an inserted roller,whiletheotherarm is connected to the pushingcylinderwith itsfree end, in this casethe other end ofthe pushing cylinder is connected with a hinge to the bottom beam.It is considered as advantageous, if the earlier mentioned lifting device has a bumperwhich prevents unmoti vated turn ofthe double-armed lever,while the bottom beam is shiftedforwards, that means thatturn of the bell crank lever is restricted.

The lifting device used with the supporting unit according to the invention may be constructed so, that actual lifting should be performed by the hydraulic working cylinder. In this case the supporting unit may be constructed so,thatone end ofthe hydraulic lifting cyilinder should be connected to thesubbase element, while the other end should be connected to the roller bearing up againstthe bottom beam orthe extension thereof.

In this case the front end of the pushing cylinder is connected to the subbase element, while the rear end is connected-similarlyto other structural versionsto the bottom beam. In these cases between the roller and the subbase element a lifting rod is inserted.

Astructurai design of the supporting unit according to the invention may be advantageous, with which the hydraulic lifting cylinder is inserted between the roller bearing up against the bottom beam orthe extension thereof and the subbase element, furtheron, if between the roller andthe front end ofthe pushing cylinder a lifting rod is inserted.

A construction can be well used in practice, with which the lifting device co-operates with a bell crank lever,which is connected rotatablytothesubbase element and on one arm thereof a roller bearing up againstthe bottom beam or the extension thereof is bedded, while between the otherarm and the subbase element a hydraulic lifting cylinder is connected.

When constructing the support unit according to the invention with a bell crank lever it can be achieved that in course of moving the support unit forward, the pushing cylinder representing the hydraulic working cylinder and per orming shifting, is lifting the support ing unit simultaneously with shifting via the bell crank lever mounted onto the subbase element, i.e. sup ported in bearings so, as to be rotatable in relation to the subbase element and pushes the supporting unit forward by sliding on the intermittent bottom beam arranged between the bottom elements.

When spanning the supporting unit-- i.e. when the cap-piece is spanned in relation to the subbase- by means ofthe duct having been formed in the subbase elements, the subbase elements are bearing up againstthe bottom beam arranged inbetween and transfer a part ofthe load to the bottom beam, as a consequencethe bearing surface will be increased and thus specific bearing pressure decreases.

With an embodimentofthesupporting unitaccord- ing to the invention, with which a separate hydraulic working cylinderisapplied in the lifting device, by means of the subbase elements lifting ofthe whole supporting unit can be achieved. Inthesecases sinking and blocking of the subbase elements can be avoided, simultaneously specific bearing pressure increases. The embodimentofthe supporting unit according to the invention provided with a hydraulic working cylinder is showing the advantageous feature, in so far as itis able to transfer-at least partly the load of the spanned supporting unit to the bottom beam.The hydraulic working cylinder can be fixedto the subbase elements, or at least to one of them, by means of a hinged mechanism, which is receiving also the forces arising normal to the working cylinder.

Accordingly, the essence of the supporting unit according to the invention lies in that the subbase is formed by a subbase element and the bottom beam connected with a hingetotheconveyorvia its extension arranged on the part facing thefrontface, and guided movable in relation to said subbase element, furtheron, it contains a lifting device connected partlyto the subbase element a partly to the bottom beam and one end ofthe pushing cylinder is connected to the lifting device orthe base, and the other end is connected to the bottom beam.

With a preferred embodiment ofthe supporting unit according to the invention the the subbase is formed by two, preferably symmetric subbase elements and a bottom beam is arranged inbetween.

With afurther preferred embodimentofthe invention the support unit is formed with an open duct enclosed by the subbase elements and receiving the bottom beam.

Anotherconstruction representsthefurtherexpe- dient embodiment ofthe supporting unit according to the invention, which is provided with ribs belonging to the subbase elements, extending into the duct and restricting the vertical motion of the bottom beams.

With a further possible preferred embodiment of the support unit according to the invention the bottom beam consists of two parts connected with a hinge.

The solution forms a fundamental embodimentof the supporting unit according to the invention, with which there is a bell crank lever belonging to the lifting device and connected rotatablyto the subbase element, and on one arm thereof a roller is embedded, while the other arm is connected to the front end ofthe pushing cylinder.

With another preferred embodiment ofthe support unit according to the invention - also representing a fundamental solutions hydraulic lifting cylinder is applied, belonging to the lifting device and one end thereof is connected to the subbase element, while the other end is connected to the roller bearing up against the bottom beam or the extension thereof, simultaneously, the frontal end of the pushing cylinder is connected to the subbase element and between the roller and the subbase element a lifting rod is arranged.

Afurtherexpedient embodiment of the supporting unit according to the invention can be characterized in that that the lifting device is provided with a bell crank lever connected rotatablyto the subbase element and on one arm a roller is embedded bearing up against the bottom beam or the extension thereof, while between the other arm and the subbase a hydraulic lifting cylinder is inserted.

The invention will be described in detail by means of preferred embodiments serving as example, by the aid ofthe drawings enclosed, wherein figure 1 is the side view of one of the embodiments of the supporting unit according to the invention, being a partial section, figure 2 is a further possible embodiment of the supporting unit according to the invention; the figure illustrates but the lifting device figure3 isthe sectional viewtaken along the plane A-Aoffigure 1, figure 4 is partly a sideview, partly a sectional view of a further possible embodiment of the supporting unit according to the invention and at last figure5 isafurtherpreferable embodimentofthe supporting unit ofthe invention, having a lifting device which differs from the earlier ones.

With the embodiment ofthe supporting unit according to the invention to be seen in figs. 1 and 2 the rod 16 is inserted between the subbase 1 and the cap-piece 12 by means ofthe hinges, the rod 16 establishes the connection between the subbase 1 and the cap-piece 12. The prop 14 is also inserted between the subbase 1 and the cap-piece 12, being as a matter offacta hydraulic working cylinder, by the aid of whichthesubbase 1 and the cap-piece 12 can be pushed apart in relation to each other. Below the series of supporting units the conveyor 18 is arranged, belonging also to the supporting equipment, which is led along the supporting equipment, in the longitudinal direction oflongwall working.In general the task is to moveforwardthe supporting equipment by means ofthe single supporting units by using the conveyor 18. In the majority of cases one proceeds so, that the conveyor 18 is pushed to thefrontal face-- according to figure 1 to the left-thereafter, after having relaxed the prop 14the single supporting units are moved aftertheconveyor 18.

As a matter of fact, the modification according to the invention manifests itself in the application ofthe lifting device 26 and construction ofthe subbase 1. As it becomes obvious from figures 1 and 3-in case of the example illustrated herethe subbase 1 consists ofthe subbase elements 10 and.the bottom beam 24 enclosed by said subbase elements. The end of the bottom beam facing the front face is connected with hinges to the conveyor 18. The part serving for establishing the connection includes the extension 25.

The bottom beam 24 can be also formed so that its separate frontal part belongs to the articulated construction, which establishes connection with the conveyor 18. In this case the bottom beam may consist of two parts connected by hinges. However, with the embodiment according to figure 1 the bottom beam 24forms an undivided unit and it is connected to the conveyor 18 at its front part via the extension 25.

As it becomes obvious from figure 3, the subbase 1 is formed ofthe two subbase elements 10 and the enclosed bottom beam 24. The bottom beam 24 is arranged in the duct 40 between the subbase elements 10. In respect two the symmetry plane 42 the whole subbase 1 is symmetrically constructed. The ribs 46 restricttheveritcal motion ofthe bottom beam 24 from above, said ribs are arranged so, as to protrude from the subbase elements 10 into the inside of the duct 40.

The actual lifting device 26 includes the bell crank lever38, which is connected by the hinge 30to the subbase element/sl 1 O. On the longer arm of the bell crank lever 38 the roller 28 is embedded. This roller 28 may bear up against the extension 25 of the bottom beam 24. The shorterarm ofthe bell crank lever 38 is connected by a hinge to one end ofthe pushing cylinder 20. The bumper 27 belongs also to the bell crank lever 38, the task ofwhich is to restrict the turn of the bell crank lever in one ofthe directions. The other end ofthe pushing cylinder 20 is connected by the hinge to the bottom beam 24. In the position according tofigure 1 everypartofthesubbaseofthesupporting unit 1 is bearing up against the bottom wall.

Operation ofthe equipment according to the invention will be explained bystartingfrom said position, as it is to be seen in figure 1. Figure shows the position after having finished the process of forward pushing, that means that both the borrom beam 24 andtheconveyor 18 have been shiftedforward. After having finished shifting of the conveyor 18, the prop 14 is to be relaxed, as a consequence, the supporting unit gets into a loosened state. Underthe influence of its own weight-the cap-piece 12 sinks to a slight extent.

In the loosened state of the supporting unit, by actuating the pushing cylinder20,the bell cranklever 38 is turning counter-clockwise at the hinge 30, interpreted on basis of figure 1. In course of said motion, by bearing up against the extension 25 by means ofthe roller 28, the subbase elements 10 emerge, as a consequence, the whole supporting unit is getting freeforthe purpose ofshifting forward, which mistaking place bythefurtheractuation ofthe pushing cylinder 20.

After having guided the supporting unit forwards, the prop 14 is repeatedlyspanned, thereafterthe adjacent supporting unit is pushed forward. After having shifted the supporting units in a predeter mined number,theconveyorl8maybe repeatedly - pushed forward. To achieve this, the pushing cylinder 20 is to be actuated in the sense of contraction. At the beginning of sa id actuating process the bell crank lever38turns as long atthehinge30clockwise linterpreted on basis offigure 1/, as the the bumper 27 is arriving atthe position illustrated in figure 1 and preventsfurtherturn ofthe bell crank lever 38.

Following the impact ofthe bumper27 the bottom beam 24 guidedbythe subbase element loins turning to the left/interpreted on basis offigure 1/and pushes the conveyorforward. The operations outlined and single steps of pushing forward areto be repeated alternatively in accordance with the rate of advancing of longwall working.

Figure 2 illustrates a preferred embodiment ofthe lifting device 26 of the supporting unit according to the invention, differing from that of the previouslyde- scribed embodiment. With this embodiment too two subbase elements 10 are used which enclose the bottom beam 24, while this latter consists of two parts.

The extension 25 is connected by the the hinge 23 to the rearpartofthe bottom beam 24. With this em bodiment the lifting device does not contain any bell crank lever, actual lifting is performed by the lifting cylinder 32. This hydraulic lifting cylinder 32 is provided with the roller 289t its lower end, while said roller is able to roll on the surface ofthe extension 25 ofthe bottom bean 24. The upper end ofthe lifting cylinder is connected bymeans ofthe hinge 31 directly or indirectly to the subbase elements 10 or at leastto one ofthem. Atthe lower end of the lifting cylinder32, expediently to the pivot carrying the roller 28, the lifting rod 36 is connected, the other end of which is connected to the subbase element 10 by means ofthe hinge 30.One end ofthe pushing cylinder 20 is fixed articulated to the subbase element 10 orto the structural partsbeing connected rigidiythereto, while the other end is connected by a hinge to the bottom beam 24, as previously described.

According to sense the embodiment according to figure 2 operates in the same manner, as the embodiment having been described in connection with figures 1 and 3. However, with the supporting unit according to figure 2 actual lifting can be achieved by forcing apartthe lifting cylinder 32, when via the roller 28, in relation to one end bearing up against the extension 25, the other end ofthe lifting cylinder lying at the hinge 31 rises and by forcing simui taneously the pushing cylinder 20 apart forward motion of the subbase elements 10 becomes possible, that means that in sense offigure 2 they advance to the left, meanwhile the roller 28 is able to move on the corresponding surface ofthe extension 25 in the earlier mentioned direction.Pushing forward of the bottom beam 24-and synchronized therewith the conveyor 18 not illustrated in figure 2-is taking place essentially in the same manner, as having been described in connection with figure 1. In this case the lifting cylinder 32 can be kept in a contracted state, while the whole supporting unit is forced apart. Under said circumstances, actuating the pushing cylinder 20 in sense of contraction, bottom beam 24 and the extension 25 connected thereto, as well asthe conveyor 18 are moving-forwards.

Figure 2 illustrates the most simple way of realiza- tion of the lifting rod 36. In ordertofulfil the task according to the invention a single-ordouble-armed linear our angular lever, or their combination can be successfully used. In such a mannerthe lifting rod 36 may be a single-armed linear lever, a single-armed bell crank lever, or a double-armed linear lever or a double-armed bell crank lever. The lifting rod 36 according to figure 2 may be considered as a special form of a single-armed lever, where the arm offorce, resp. the arm of load are of identical length.

The embodiment ofthe bottom beam according to figure 2-wherein the bottom beam consists oftwo parts connected by the hinge 23-can beadvan- tageously used, if due to the waviness ofthe basethe waviness is to be followed within a short tract.

Figure 4 shows a further possible embodiment of thè supporting unit according to the invention. With the embodimentto be seen here the lifting device 26 is provided with a lifting cylinder 32, similarly to the previously described solution, the bottom beam 24 consists also oftwo parts, whereby the bottom beam 24 and the extension 25 are interconnected by means ofthe hinge 23. With this embodiment the upper part of the lifting cylinder 32 is connected to a construction via the hinge 31, which is fixed to the subbase elements 10 or at least to one of them. The lower part of the lifting cylinder 32 is connected to the roller 28, whilethe lifting rod 36 is connected to the axis ofthe roller, the opposite end ofthe lifting rod may be connected to the pushing cylinder 20 via the hinge 30, whereas the hinge 30 is installed to the subbase element 10.

Similarlyto the earlier described embodiments, the opposite end ofthe pushing cylinder is connected to the rear part ofthe bottom beam 24throughthe hinge.

With the embodiment according to figure 4 operation is taking place in the same manner, as with the embodiments previously described. In this case too, if the lifting cylinder 32 is forced apart,thesubbase element 10 is raising in relation to the bottom beam 24 togetherwiththewholesupporting unit,simul- taneously by forcing the pushing cylinder 20 apart, the whole supporting unit can move to the left/intepreted in sense offig. 4/. In course of said motion the roller 28 connected in a rotatable mannerto the lower part of the lifting cylinder 32-is ableto roll in direction ofthe conveyor 18 on the extension 25 or on the correspond- ing tract ofthe bottom beam.It goes without saying that during the period oftrailing forward the supporting unit, the prop 14 is relaxed, accordingly, the cap-piece occupies its sunken position. The bottom beam 24 and the conveyor 18 are pushed forward, as previously described. In this sensethe supporting unit is to be forced apart, that means that the cap-piece 12 is pressed onto the roof by means of the prop 14, thereafter, having contracted the lifting cylinder 32 the pushing cylinder is to be actuated also in sense of contraction and as a matter of fact, as a result of this activitythe bottom beam 24 and the conveyor 18 connected thereto will be able to move in direction of the frontal face.

Figure 5 shows a further possible embodiment of the lifting device 26 ofthe supporting unit according to the invention. With this embodiment both the bell crank lever 38 and the lifting cylinder 32 are applied.

The bell crank lever 38 is connected to the subbase elements 1 Othrough the hinge30, said hinge may be connected to one end ofthe pushing cylinder 20. In this case the longer arm ofthe bell crank lever 38 carriesthe roller 28 which is bearing up against the proper surface ofthe extension 25. The shorter arm 37 ofthe bell crank lever is connected to one end of the lifting cylinder 32, while the opposite end ofthe lifting cylinder is connected to the subbase element 10 with the hinge 32.

While shifting the supporting unitaccordingtothe invention illustrated in figure 5, in addition to the relaxed prop 14 and in compliance therewith, to the cap-piece 12 being in its sunken position, by putting the pushing cylinder 20 in motion in the opening sense and actuating the lifting cylinder 32 also in opening sense,the bell crank leverturns aroundthe hinge counter-clockwise ensuring in such a manner lifting of the subbase elements 10 and therewith ofthe complete supporting unit, simultaneously, as a consequence of the actuation ofthe pushing cylinder 20 in opening sense the supporting unitthusliftcan be shifted forwards /interpreted in sense offigure 5 to the lefts The bottom beam 24 is shifted forwards so, that the supporting unit is brought into a tensed state, whereafterthe lifting cylinder is brought in the contracted position. In the following phase of operation the pushing cylinder 20 is actuated in sense of contraction, as a consequence, both the bottom beam 24 andthe conveyor 18 connected thereto are moving to the left /in sense offigure 5/i.e. to the front face.

From the description ofthe supporting units serving here as example - it becomes obvious that the supporting units having been provided with the lifting devices according to the invention are constructed in a most simple way, they do not change the usual structural design of the supporting unitstraditionally accepted, in addition, lifting ofthe supporting unit can be performed with an utmost good efficiency, also in cases, in which-dueto insufficient strength of the bottomthe supporting unittends to sinking.

Due to the specific design ofthe construction the subbase has a large surface keeping the specific bearing pressurewithin thetolerablevalues, atthe same time this specific bearing pressure is anyway more advantageous, than when using any other construction serving for the same purpose. As an advantage the circumstance should be mentioned, in so farads the main hydraulicelement/s/ofthe supporting unit-in ourcasethe prop 14-need not be chosen so, as being suitable for a two-way operation, because only an unidirectional force is needed.

lnthefollowingclaims, reference numerals are given as an aid tothe readerwhich refertothe corresponding parts ofthe drawings. These reference numerals are not intended to restrict the claims in any way.

Claims (11)

1. Supporting unitforunderground longwall workingfora mechanized supporting equipment, including a subbase, a cap-piece, the articulated rod interconnecting them, the hydraulic prop inserted between the subbase and the cap-piece, as well as the hydraulic pushing cylinder serving forforward shifting, being connected with one end indirectly to the conveyorlyingalongthelongwall underwork, characterized in thatthe subbase/l/is formed bythe subbase element/l O/and by the bottom beam /24/ being movable in relation to said subbase element and connected to the conveyor/18/ th roug h the extension /25/ arranged on the part facing the longwall,furtheron, it is provided with a lifting device /26/connected pa rtly to the subbase element /10/ and partlytothe bottom beam/24/and one end ofthe pushing cylinder/20/is connected tothe lifting device /26/onto the subbase element/I 0/, while the opposite end is connected to the bottom beam /24/.

2. Supporting unit as claimed in claim 1, characte rized in that the subbase /1/ is formed of two, preferably symmetric subbase elements /10/ enclos ingthebottom beam /24/.

3. Supporting unit as claimed in claim 2, characte rized in that it includes an open duct /40/ receiving the bottom beam/24/and enclosed bythesubbase elements /10/.

4. Supporting unit as claimed in claim 3, characte rized in that the ribs /46/ belonging to the subbase elements /1 0/are extending into the duct/40/ and restrict the vertical motion ofthe bottom beam 1241.

5. Supporting unit as claimed in any ofthe claims 1 to 4, characterized in that the bottom beam /24/is composed of two parts interconnected with a hinge 1231.

6. Supporting unit as claimed in any ofthe claims 1 to 5, characterized in that it has a bell crank lever/38/ belonging to the lifting device /26/which is connected to the subbase element/10/ a a rotatable manner, one arm of which is carrying the roller/28/ bearing up against the bottom beam /241, while the other arm /37/ is connected to the front part of the pushing cylinder /20/.

7. Supporting unit as claimed in any ofthe claims 1 to 5, characterized in that it includes a hydraulic lifting cylinder/32/ belonging to the lifting device/26/, one end of which is connected to the subbase element/10/, while the opposite end is connected to the roller/28/ bearing up against the bottom beam /24/orthe extension /25/thereof, furtheron, the front end ofthe pushing cylinder/20/ is connected to the subbase element/lOJand a lifting rod /36/ is inserted between the roller/28/ and the subbase element /10/.

8. Supporting unit as claimed in any ofthe claims 1 to 5, characterized in that the lifting device /26/has a roller/28/bearing upagainstthe bottom beam/24/or the extension /25/thereof, a a hydraulic lifting cylinder /32/arranged between said roller and the subbase element/1 0/, furtheron, between the roller/28/and the front end ofthe push cylinder/20/a lifting rod /36/ is inserted.

9. Supporting unit as claimed in any of the claims 1 to 5, characterized in that a bell crank lever/38/ connected rotatablyto the subbase /10/belongs to the lifting device /26/, one arm of which carries a roller/28/ bearing up against the bottom beam /24 orthe extension /25/thereof, while between the other arm /37/andthe subbase element/lOla hydraulic lifting cylinder/32/ is inserted.

10. Asupporting unitsubstantiallyashereinbe- fore described in connection with and as illustrated in anyofFigures1 and 3, 2,4or5.

11. A mechanised support including a supporting unit as claimed in any one of claims 1 to 10.