A working machine for which an inventive arrangement is adapted shall include, among other things, mutually parallel arms which will enable an implement or tool to be attached to, but readily removable from, an implement holder, a first piston-cylinder arrangement that coacts with each arm, such as an arrangement by means of which the working implement can be pivoted or tilted about a first horizontal pivot axis, a second piston-cylinder arrangement coacting with each arm and enabling the working implement to be raised and lowered about a second horizontal pivot axis, and a locking piston arrangement which is movable between a position in which the working implement is locked to the implement holder of said machine and a position in which the working implement is released from said implement holder, where one, or normally two, locking pistons are arranged for movement towards and away from said positions and if two pistons also towards and away from each other.

The invention is also advantageously based on a working machine that could include such properties as those whereby each of said mutually parallel arms includes a lifting arm system that can be assumed to consist of a main arm (having a lifting part) which is

pivotally attached to the chassis of the working machine, and an arm-part which is attached to the main arm or formed integrally therewith and therewith angled relative to said main arm, and an implement holder attached to the free ends of the two arm-parts and said piston-cylinder arrangement.

Thus, the present invention can be applied more specifically with a working machine with which one end of each of the two mutually parallel main arms is pivotally attached to the chassis of the working machine via an individual lifting device, with the arms being raisable and lowerable by means of its respective second piston-cylinder arrangement, and with a second end (an outer end) of respective arm-parts being pivotally mounted and pivotally related to an implement holder.

In order to facilitate an understanding of the following descrip- tion, the meaning of the terms "pivotally attached" and "spheri- cal pivot means" will now be described.

By "pivotally attached" is meant a pivotal attachment where pivotal movement can only take place, or essentially only take place, about one single pivot axis, and by "spherical pivot means" is meant a pivotal attachment which enables selective rotational movement to take place and which is required for the function of the invention, such as about a pivot means having a selected pivot axis orientated through said means and with the pivotal axis oriented in the same plane or in a plane that deviates slightly from the pivot axis that is dominant in the "pivotal attachment".

This enables the pivot axis to be selected within narrow limits.

A "spherical pivot means" need not necessarily include a "sphere", and may comprise other means that will provide the

intended technical effect, such as cardan couplings and like couplings.

DETAILED DESCRIPTION OF THE BACKGROUND ART Various different designs of working machines of the kind defined in the introduction are known to the art, these machines compris- ing mutually parallel arms that can be considered to consist of two parallel arm-systems of which each could include a main arm and an arm-part that includes a cross beam which interconnects the arm systems, and where the arms of said two arm systems shall be capable of coacting with an implement holder.

The two arm systems are non-rotatably connected with one another through the medium of said cross beam, wherewith a heavy load, an unbalanced load, acting on one arm system will be transmitted to the other arm system via the cross beam.

The machine includes a first piston-cylinder arrangement, one for each arm, whereby the implement holder, and thus also an imple- ment or tool attached to the holder, can be pivoted or tilted, and includes a second piston-cylinder arrangement whereby the implement holder can be raised and lowered.

With respect to the inventive feature of adapting two piston- cylinder arrangements as lift cylinders that are hydraulically connected in series so as to enable respective lift cylinders in the lift arm system to take-up part of the load acting on a lift arm, it is known to choose different surface areas for series- connected piston-cylinder arrangements so as to afford an equivalent effect and force.

An example of this latter feature is found in publication GB-A-1 183 676, which teaches a table that is raised and lowered in a

scissor-like manner with the aid of series-connected piston- cylinder arrangements.

With regard to the ability of moving an implement laterally away from and towards the normal plane of the working machine in accordance with the present invention, it can be mentioned that it is known to move an implement sideways with the aid of pivotal attachments parallel with an attachment beam that serves as a cross beam, with the aid of a parallelogram arrangement.

As example of the earlier standpoint of techniques in this regard is found in French Patent Publication 1 546 020.

This publication describes and illustrates a working machine which includes mutually parallel beams or bars 21a, 21b for holding an implement or tool 13, 25, 26, 27 through the medium of an implement holder 22, and to enable the implement 13 to be displaced laterally from a normal plane or central plane through an angle which delimits a right angle in both directions, by means of an hydraulic piston-cylinder arrangement 30.

According to the French publication, respective one ends of the main arms 21a, 21b are pivotally attached to the chassis of a working machine, for pivotal or rotary movement solely in a vertical direction. The other ends (the outer ends) of the two main arms have a pivotal attachment 28 and are orientated so as to enable a tool or implement to be rotated about the pivot and therewith move the implement and the implement-holder laterally in a horizontal direction.

To this end, the main arms 21a, 21b and the beam 22 have been given the form of a U-shaped flexurally rigid unit with the beam or base 22 of the U-configuration serving as an implement holder.

The arrangement 13, 25, 26, 27 functioning for lateral movement of the implement, among other things, can be considered as a separate unit, with the implement placed far forwards of the working machine, which will probably make the machine "nose heavy" when handling a heavy load.

A beam 27 extends transversely across the free ends of the main arms, where the implement holder is mounted.

A single support beam 25 is positioned centrally of the cross beam 27 and is rotatably or pivotally attached at one end to the beam 27 on a vertical pivot axle, and is similarly pivotally attached at its other end to the implement 13.

The implement holder can be moved sideways horizontally with the aid of a piston-cylinder arrangement 30, although with the use of two mutually parallel guide arms 32.

With respect to the inventive feature of enabling the implement holder, and therewith the implement, to be skewed or tipped relative to a plane (a horizontal plane) perpendicular to a normal movement direction of the working machine, various constructions are known in mutually different technical fields and applications.

By way of example of the present standpoint of techniques, it can be mentioned that a tool or implement can be caused to coact with different devices so as to bring the implement or tool into selected alignment with a horizontal plane, and that it is also known to tip or incline the implement with the aid of edge- related piston-cylinder arrangements that are hydraulically operated.

Road planers or graders are examples of machines in which skewing of a working tool for adjusting the position of a scraper in relation to a horizontal plane for providing the road surface with a specified camber is a dominant feature.

SUMMARY OF THE INVENTION TECHNICAL PROBLEMS In view of the fact that the technical deliberations required of a person skilled in this particular art in providing a solution to one or more technical problems involve initially a realization of the measures and/or the sequence of measures that must be undertaken on the one hand, and a choice of the measure or measures required on the other hand, it will be seen that the technical problems listed below are relevant to the development of the present invention.

When considering the present standpoint of techniques as de- scribed above with respect to a working machine of the kind defined in the introduction, it will be seen that a technical problem resides in providing such conditions for the lift arm system used as to enable with a primary selection of one of the functions lateral displacement of the implement, skewing of the implement, or connecting in series the two piston-cylinder arrangements that function as lift cylinders so as to cause each piston-cylinder arrangement to essentially take-up its share of the load acting on the lift arm conditions whereby each of the remaining functions can be obtained without or with minor additions.

With respect to creating conditions in the present field of application whereby respective piston-cylinder arrangements for respective lift arms shall be able to take-up the load acting on

the lift arm concerned, it will be seen that a technical problem resides in providing conditions whereby the mutually parallel arms will obtain a stable construction even when the implement is loaded obliquely, and with actuation of the piston-cylinder units included in the piston-cylinder arrangements correspondingly to the load.

With respect to this technical application, it will be seen that a technical problem resides in realizing the significance of and advantages afforded by connecting a first piston-cylinder unit in series with a second piston-cylinder unit, wherewith both units serve in a second piston-cylinder arrangement.

Yet another technical problem is one of realizing the conditions that must be provided in order to enable the speed and/or the length of stroke of one piston to be so adapted and selected that it reaches an outwardly extended end-position from a starting position simultaneously with the other piston, and vice versa, therewith creating conditions for adapting the surface areas of the piston-cylinder units equal or different.

Another technical problem is one of realizing the conditions for allowing a triangle-related attachment of the first piston- cylinder unit and an adjacent main arm to be identical to a triangle-related attachment of the second piston-cylinder unit and an adjacent main arm, therewith creating conditions for using piston-cylinder units that have mutually the same surface area.

It will also be seen that a technical problem is one of realizing the significance of allowing the mutually parallel arms to be actuable independently of each other and with a cross beam pivotally attached to the lift arms and adapted so as not to transfer load between the lift arms, or to transfer such load to

only a insignificant extent, depending on different setting positions.

Another technical problem is one of creating conditions whereby an implement mounted in an implement holder can be moved stably sideways to an adapted extent in relation to the central plane of the working machine, said plane being orientated in a normal direction of movement of said machine.

Another technical problem is one of realizing the significance of and the consequences related to creating conditions such that respective first ends of the main arms can be rotatably related to the chassis of the machine through the medium of "spherical pivot points" so as to provide movement in at least two perpen- dicular, different coordinates, and such that a third piston- cylinder arrangement will be able to move the free-ends of the main arms laterally and therewith also the implement holder.

Another technical problem is one of realizing the advantages that are afforded when said horizontal, lateral movement is relatively small to and from a vertical plane extending centrally in the longitudinal direction of the working machine.

Another technical problem is one of realizing the significance of and the implications associated with adapting said lateral movement solely between two mechanical stop shoulders or through a distance corresponding to an adapted length of stroke of a third piston-cylinder arrangement.

Another technical problem is one of enabling the implement holer to move laterally within an angular value of +10° while maintain- ing a stable lift arm construction.

It will also be seen that a further technical problem is one of realizing the significance of and the simplicity in attaching the arms to the machine chassis through the medium of spherical pivot points with the aid of universal bearings.

Still another technical problem is one of realizing the signifi- cance of and the advantages afforded by adapting each of said mutually parallel arms such that the pivotal attachment of one end of the main, adapted to a movement in perpendicular coordi- nates, the pivotal attachment of the second piston-cylinder arrangement through the medium of at least one spherical pivot point, and the similarly provided pivotal attachment of the implement holder, shall be orientated in one and the same vertical plane.

Still yet another technical problem is one of realizing the significance of allowing the thus allocated vertical planes to be oriented symmetrically by the side of said central vertical plane.

Yet another technical problem is one of realizing the signifi- cance of increasing stability and restricting the space require- ments by duplicating the third piston-cylinder arrangement such as to enable each of said arrangements to act between a central part of the implement holder and one of the lift arm systems.

When considering the present standpoint of techniques as de- scribed above with reference to a working machine, it will be seen that a technical problem resides in constructing an imple- ment holder in relation to mutually parallel arms that will enable the holder and an implement carried thereby to be skewed in a first direction, by activating a first piston-cylinder unit included in a second piston-cylinder arrangement, and to be skewed in a second direction by activating said first piston-

cylinder unit included in said second piston-cylinder arrange- ment, and by pivotally and tiltingly attaching the implement holder in members belonging to the free ends of the lift arms, through the medium of spherical pivot points.

It will also be seen that a technical problem is one of realizing the significance of and the advantages afforded by creating within a hydraulic circuit conditions which, in addition to normal activation of the second piston-cylinder arrangement, enable the second piston-cylinder unit to be latched in position when activating the first piston-cylinder unit.

Another technical problem is one of realizing the significance of and the advantages afforded by including in the hydraulic fluid line leading to one of said piston-cylinder units a device that limits the volume of hydraulic fluid and therewith causes limited skewing movement through the medium of an activated first piston- cylinder unit.

It will also be seen that a technical problem resides in realiz- ing the significance of and the advantages afforded by incorpo- rating a bypass line with a tap or cock parallel with said hydraulic fluid restricting device.

SOLUTION With the intention of providing a solution to one or more of the above technical problems, the present invention relates to an arrangement which obtains particular application in a working machine of the kind described in the introduction, with a main arm pivotally attached to the machine chassis.

With the intention of providing a solution for one or more of the aforesaid technical problems with respect to the distribution of

the lifting force on the piston-cylinder units belonging to said lift arms in dependence on the load on respective lift arms, it is proposed that the main arms or the lift arms of a working machine of the kind described in the introduction can be swung up and down independently of one another, or at least essentially independently of one another, and that the first piston-cylinder unit is connected hydraulically in series with the second piston- cylinder unit.

It is also proposed in accordance with the invention that the speed and/or length of stroke of one piston is adapted and chosen on the basis of a starting position in which the piston is extended to an end position simultaneously with the other piston.

The invention also proposes a triangle-related attachment of the first piston-cylinder unit and an adjacent lift arm or main arm is equivalent to a triangle-related attachment of the second piston-cylinder unit and an adjacent lift arm or main arm, and that the units have mutually equal surface areas.

With the intention of enabling horizontal, sideways movement of the implement holder and an implement carried thereby, one end of the main arm is pivotally mounted on the chassis by means of a spherical pivot which enables said end to move in at least two mutually perpendicular coordinates, and a third piston-cylinder arrangement is arranged for sideways movement of said implement holder with mutually parallel main arms.

In accordance with further embodiments that lie within the scope of the inventive concept, sideways movement of said implement holder is effected away from and towards a central vertical plane extending in the longitudinal direction of the machine.

With the intention of avoiding fracture stresses on the spherical pivot attachments of the main arms, it is proposed that sideways movement of the implement holder is restricted to an angle of +10° between two movement-limiting mechanical stop shoulders or the like.

It is also proposed that each of the main arms is attached to the chassis with the aid of a respective universal bearing.

It is also proposed in accordance with the present invention that each of said parallel-related components is so adapted that the attachment of one end of the main arm through the medium of a spherical pivot for pivotal movement in mutually perpendicular coordinates, the pivotal attachment of the second piston-cylinder arrangement, through the medium of at least one spherical pivot, and the spherical, pivotal attachment of the implement holder are orientated in one and the same vertical plane.

It is also proposed that the vertical planes are orientated laterally of said central vertical plane.

It is also proposed that the third piston-cylinder arrangement is duplicated, so that each arrangement will be able to act between the implement holder and one of the lift arm systems.

It is also proposed that the main arm or a lift arm related thereto shall be pivotally related to said implement holder via a spherical pivot for movement in at least two mutually perpen- dicular and different coordinates.

With the intention of providing a solution to one or more of the aforesaid technical problems, there is proposed an arrangement pertaining to a working machine which has the features disclosed in the preamble, among other things.

A particular significant feature of the invention is that the implement holder and an implement carried thereby can be skewed in a first direction, by activating a first piston-cylinder unit included in said second piston-cylinder arrangement and skewed in a second direction by activating the first piston-cylinder unit included in said second piston-cylinder arrangement, and that the implement holder is pivotally and tiltingly mounted in means belonging to the main arms and/or the lift arms.

According to preferred embodiments that lie within the scope of the inventive concept, means are provided for latching the second piston-cylinder unit in position when activating the first piston-cylinder unit.

It is also proposed that there is included in a hydraulic fluid line to one of said piston-cylinder units a device which func- tions to limit the amount of hydraulic fluid delivered to said unit and therewith restrict the movement said piston-cylinder unit and therewith also skewing of the implement holder.

The invention also includes the provision of a tap or cock fitted in a bypass line and connected in parallel with the hydraulic fluid restricting device.

ADVANTAGES The advantages that can be considered primarily characteristic of an inventive arrangement reside in the creation of provisions through the medium of a series-coupling of piston-cylinder arrangements and separate raising of the two main arms or lift arms via a respective piston-cylinder arrangement for allowing each arrangement to take-up solely, or essentially solely, the load acting on its respective lift arm.

Those advantages primarily afforded by an arrangement in working machines reside in the provision of conditions whereby the basic construction of the mutually parallel main arms or lift arms can be maintained not only by letting the main arms being parallel but also pivotally attached to one another while, nevertheless, creating provisions which will enable the implement holder to be moved horizontally sideways, and therewith also the implement carried by said holder, with the aid of a third piston-cylinder arrangement by virtue of a spherical pivot attachment of the two main arms to the chassis and a corresponding attachment between the two main arms or lift arms of the implement holder.

The advantages that can be considered primarily characteristic of an arrangement reside in the provision of conditions by which the implement holder and an implement carried thereby can be readily skewed by actuation of a first piston-cylinder unit within a second piston-cylinder arrangement. It is necessary for the implement holder to be pivotally mounted to the lift arms for movement in all directions, in order to enable the implement to be raised, lowered and skewed.

The primary characteristic features of an inventive arrangement pertaining to a working machine are set forth in the characteriz- ing clause of the following Claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS An inventive arrangement and an application of two different, mutually parallel arms of a working machine will now be described

in more detail with reference to the accompanying drawings, in which Figure 1 is a perspective view of a first embodiment of two mutually parallel arms which are intended to hold an implement or tool and which are constructed to enable the implement holder and the implement to be moved sideways or skewed, and/or to allow each lift cylinder to take-up solely, or essentially solely, the load acting on its lift arm; Figure 2 is a perspective view of a second embodiment that includes alternative forms of the mutually parallel arms; Figure 3 illustrates an hydraulic circuit particularly adapted for the embodiment shown in Figure 2; and Figure 4 is a horizontal, sectioned view of a spherical pivot suitable to the function of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS AT PRESENT PREFERRED Figure 1 is a perspective view of a first embodiment that includes two mutually parallel assemblies "M", "M"' forming part of an arrangement belonging to a working machine "A".

<BR> <BR> <BR> <BR> <BR> <BR> <BR> Because the two mutually parallel assemblies "M", "M'" are identical, the following description is concentrated solely on one assembly "M" and reference signs associated therewith, whereas corresponding components of the other assembly "M'" are identified with the same reference signs to which a prime has been added.

Such an assembly "M" can be said to comprise an arm system that includes a main arm 1 and an arm-part attached thereto, or preferably formed integrally therewith, said arm-part being somewhat angled to the main arm 1 and referred to in the follow- ing as the lift arm or secondary arm 2. The main arm 1 and the secondary arm 2 may be telescopically arranged.

Extending between the lift arms or arm-parts 2, 2' is a cross beam 4 and an implement holder 5 which coacts with the free ends of the lift arms 2, 2' and which is intended to hold an implement or tool (not shown but indicated at 5'), in the form of a bucket, plow or like implement.

The beam 4 is pivotally attached at its ends 4a, 4b to the arm- parts 2, 2' such as to permit "free" movement of the two arms 1, 2; 1', 2'.

However, there is nothing to prevent the attachment from being slightly flexurally rigid or the beam 4 to be made slightly flexible with illustrated attachments for the ends 4a, 4b.

A first piston-cylinder arrangement 6, 6' that includes two piston-cylinder units 61, 61' is provided for pivoting or tilting the implement 5' about a first pivot axis 7, a second means- associated piston-cylinder arrangement 8, 8' including two piston-cylinder units 81, 81' is provided for swinging the implement 5' or the implement holder 5 up and down about a second pivot axis la'.

The implement holder 5 includes a double-acting locking piston 10a, 10b which function to move a position in which the implement 5' is locked to the implement holder 5 of the working machine and a position in which the implement 5' is released from said implement holder 5, wherewith movement of said locking pistons

10a, lOb between said positions is achieved in a known manner with the aid of a lever arm system 10, not shown.

The lever arm system 10 may be replaced with a system that is manoeuvered by a piston-cylinder arrangement, not shown.

The arm assembly "M" includes an arm system 1, 2 that includes a main arm 1 whose one end la is pivotally attached to the chassis "A" through the medium of an attachment 3 and also through the medium of a spherical pivot or rotational shaft la'.

When the second piston-cylinder arrangement 8 is extended, the implement holder 5 is lifted. Conversely, the implement holder 5 is lowered when the piston of the second piston-cylinder arrange- ment 8 is retracted.

The other end lb of the main arm 1 is related to and merges with one end 2a of a lift arm 2, the other end 2b of which is pivotal- ly mounted on the implement holder 5 by means of a spherical pivot 7.

A schematically illustrated cross arm 4 may be pivotally mounted to the lift arm 2 and 2' respectively within the centre region of the arms, by means of mutually opposing spherical attachments in the ends 4a, 4b. The attachment 4a, 4b have not been shown in detail, although they may have the form illustrated in Figure 4.

The construction is based on the provisions of means which will enable the implement holder 5 to be moved sideways horizontally in the directions P1 and P2 in Figure 1, and therewith also the implement 5' carried by the implement holder 5.

This sideways movement of the implement holder is achieved with the aid of a third piston-cylinder arrangement which is not shown in Figure 1 but which is referenced 12 in Figure 2.

The pivot la' and the attachment 7 function, in accordance with the invention, to provide a vertical first movement in the general direction of movement, and a restricted second movement in the horizontal plane.

Sideways movement is adapted from and towards a vertical plane "V" extending centrally through the working machine "A" in the direction of its normal movement.

The extent of sideways movement of the implement holder may be restricted by two mechanical stop shoulders, so as not to overload the attachments la' and 7.

There is nothing to prevent hydraulic restrictions from being used, by dimensioning and mounting the third piston-cylinder arrangement 12 in an appropriate manner.

The stop shoulders or like devices may be adapted to allocate the mutually parallel main arms 1, 1' and the mutually parallel lift arms 2, 2' and angle of +10° in relation to a vertical plane "V".

The arms 1, 1' may be conveniently attached (la') to the chassis "A" with the aid of a respective universal bearing.

In the illustrated construction, each of the mutually parallel assemblies "M", "M'" is so adapted that the attachment la' of one end la of the main arm 1 and the arm-part 1 pivotal in mutually perpendicular coordinates is also used for at least one pivotal attachment 8a of the second piston-cylinder arrangement 8 and also the pivotal attachment 7 of the implement holder 5.

The thus allocated vertical planes "V1", "V2" shall be symmetri- cally oriented laterally of the central vertical plane "V".

Figure 2 illustrates an alternative arrangement to the embodiment shown in Figure 1.

Those components that are the same as or find correspondence in the Figure 1 embodiment have been identified by the same refer- ence signs as far as possible.

The Figure 2 embodiment, however, includes a third piston- cylinder arrangement 12 which includes two diagonally positioned units (12, 12'), and it will be evident that extension of one unit 12 will cause the implement holder 5 to move to the left, while retraction or shortening of the unit will cause said holder to move to the right.

Each of the third piston-cylinder arrangements 12, 12' shall act between the centre part of the implement holder 5 and one of the arm assemblies "M", "M'".

In the Figure 2 illustration, there is connected to a working machine "A", a tractor or like machine, hydraulically operated main arms or load arms 1 and 1' which are connected at one end la thereof to attachment or lift-off brackets 3 and 3' by spherical pivots 17, 17'.

The piston-cylinder arrangements 8, 8' or the lifting cylinders 81 and 81' are mounted between the brackets 3 and 3' and the region of the angled arm-parts 1, 2 and 1', 2'.

One end 8a of the piston-cylinder arrangement 8 is attached to the bracket 3 by a spherical pivot 19 at an adapted distance beneath the spherical pivot 17 of the arm 1, and the other end 8b

of said arrangement 8 is attached close to the outer end-part lb of the load arm 1 suitably by a spherical pivot 18.

Extending adjacent each of the load arms 1 and 1' is a link arrangement, each of which comprises a piston-cylinder arrange- ment 6 that includes a hydraulic cylinder 61 which is pivotally mounted to the attachment bracket 3 by a spherical pivot 6a and is adapted to rotate an implement frame or implement holder 5 around an attachment pin 7 mounted on the outer ends of respec- tive arm-parts 2 and 2', via a pivot 6b, a pivot link 10 and a guide link 11.

The guide link 11 and the hydraulic cylinder 6 may change places if considered suitable.

The attachments between brackets 3 and 3' and the load arms 1 and 1' permit rotation about respective pivot points in both a vertical and horizontal direction up to a given angle of rota- tion.

The same mobility applies between the attachments 3, 3' and the hydraulic cylinders 61, 61' between attachments 3 and 3' and the hydraulic cylinders 81, 81', between the arms 1, 1' and the implement frame 5, and between the guide links 11, 11' and the implement frame 5.

Extending between the implement frame 5 and diagonally towards each of the arms 1 and 1' are hydraulic cylinders 12, 12'. These cylinders are also pivotally mounted at both ends by spherical pivots.

Extending between the arms 1 and 1' is a brace 14 (corresponding to the beam 4 in Figure 1) which is pivotally mounted at both ends by spherical pivots 14a, 14b and attached to the arms 1 and

1' as far as possible from a line between the attachment points 17 and 17'.

When the implement holder 5 stands straight upwards, so that an angle between the implement frame 5 and the arms 1 and 1' is the same on both the right and the left side, the line between the pivots 17, 18, 19 define a triangle which is equal to the triangle defined by the lines extending between the pivots 17'm 18' and 19'.

These triangles are congruent.

The lengths of the cylinders 81 and 81' correspond to one side of the equilateral triangles and are proportional to one another with respect to oil-volume/cm length on each side of the piston 20 of the hydraulic cylinder 81.

Figure 3 shows that the hydraulic cylinders 61, 61' for tilting the implement 5' are connected in parallel to a section 21a of a directional valve 21.

The piston-cylinder arrangement 12 is connected to another section 21b of the valve 21.

The piston-cylinder arrangements 8 and 8' are connected in series to a section 21c and 21d of the directional valve 21 in a manner such that a line 22 extends from the valve to the bottom side of the cylinder 81 and further from the top side of the cylinder 81 via a line 23 to the bottom side of the cylinder 81' and from the top side of the cylinder 81' to the same valve section as that to which the line 22 is connected, via a line 24.

A line 25 extends from another valve section 21d to a slave cylinder 26 which includes a loose piston 27 that can move

reciprocatingly in the cylinder and prevents the volume of oil passing through exceeding the volume of the cylinder.

A bypass connection between the lines 25 and 23 can be fully opened with the aid of a cock 28 so as to set the skewing angle, whereafter the cock is closed so that the slave cylinder 26 and its piston 27 can fulfil their intended function.

A line 29 extends from the line 24 to the same valve section 21d as the line 25.

When a load is to be lifted, the line 22 is pressurized and the line 24 is placed in connection with a tank, wherewith the piston 20 of the cylinder 81 is pressed upwards and oil is pressed out in the line 23 that leads to the bottom side of the cylinder 81', whereafter oil departs from the piston side of the cylinder 81' to said tank, via the line 24 and the valve 21.

The volume of oil pressed-in through the line 22 is greater than that pressed out through the line 24, due to the surface area of the piston rod.

Since the ratio of incoming oil volume to outgoing oil volume in respect of the cylinder 81 is equal to the ratio between the sides of the equilateral angles 17, 18, 19 and 17', 18' and 19', the arms 1 and 1' will be moved uniformly.

The arms 1 and 1' will also be lowered uniformly when the load is lowered.

If the two arms are loaded with mutually different forces, this will have no effect on movement of the arms and the load will not be shifted over between the lift arms, as would be the case if the lift cylinders were connected in parallel.

When the implement frame 5 is to be pivoted or skewed in relation to the attachments 3 and 3', the hydraulic cylinder 81' can be manoeuvered independently of the cylinder 81 through the lines 25 and 29, whereupon the cylinder 81 remains stationary because the line 22 that is pressurized when the arm 1 is pressurized is closed.

When the cock 28 is closed, the cylinder 81' can move to only a limited extent when the lines 25 and 29 are pressurized, because the piston 27 in the slave cylinder 26 will only allow a certain volume of oil to pass through, after which the piston is unable to move. This restricts pivotal movement of the implement frame 5, such restriction being necessary in order to prevent fractur- ing of the bearings. The pivotal range is adjusted by opening the cock 28, so that an unlimited volume of oil is able to pass through the lines 25 and 29.

Manoeuvering of the hydraulic cylinder 12 (and/or 12') results in a change in the angles between the arms 1 and 1' and the imple- ment frame 5, wherewith the implement frame 5 is moved sideways.

The arms 1 and 1' are held upright, when the attachments 14a, 14b of the brace 14, the attachment 7 between the implement frame 5 and the arm-parts 2 and 2', and attachments 17 and 17' do not lie on one and the same line.

In addition to lifting and lowering and rotating an implement frame or holder 5 around the axis of the implement frame 5, the load arms 1, 2 and 1', 2' of the inventive arrangement are also able to change the angle of the implement frame in relation to the pivot attachments 3 and 3' and also move the implement frame sideways.

These additional movements enhance the ability of the machine to handle material smoothly and also to plane and grade road surfaces, clear away snow, etc.

Skewing of the implement holder or frame 5, and therewith skewing of the implement 5' carried by said holder, in a first direction F1 is effected by activating a piston-cylinder unit 81' in the second piston-cylinder arrangement 8, whereas skewing in another direction is effected by activating the same piston-cylinder unit 81' in said second piston-cylinder arrangement 8.

The second piston-cylinder unit 81 is latched in position when activating (via 21d) the first piston-cylinder unit 81'.

Particular reference is made to the provision in an hydraulic oil line to one of said piston-cylinder units of a device 26, 27 that limits the volume of hydraulic oil to said unit and therewith restricting the movement of said piston-cylinder unit 81.

The speed and/or dimensions of one piston is/are chosen so that said piston will reach an extended end-position at the same time as the other piston.

A triangle-related attachment of the first piston-cylinder unit 81' and an adjacent main arm is identical to a triangle-related attachment of the second piston-cylinder unit 81 and an adjacent main arm.

In the case of equilateral triangles, different piston-cylinder arrangements 8, 8' are required in respect of different triangles and similar areas for the piston-cylinder arrangements 8, 8' can be used.

A chosen relationship between said triangle-related attachments is chosen to correspond to corresponding relationships between the piston-cylinder arrangements.

Figure 4 illustrates the principle of one embodiment of a spherical pivot means suitable for use with the invention.

Attached to the chassis "A" is a bracket structure 3 that includes two attachment lugs 41, 42, between which a shaft 43 is fixedly or rotatably mounted.

The shaft 43 includes a sphere 44 which coacts with a correspond- ing aperture 45 in the arm la, therewith enabling the arm 1 to be swung in all directions at the part la.

The attachment lugs 41 and 42 may conveniently form the aforemen- tioned stop shoulders 46, 47.

It will be understood that the invention is not restricted to the aforedescribed and illustrated exemplifying embodiments thereof and that modifications can be made within the scope of the inventive concept as defined in the following Claims.