Each leg is positioned at the front part of the chassis and is pivotally mounted thereon by means of a respective side- positioned pivot shaft.

The present invention is also based on the concept of mounting each wheel assembly in a respective frame arrangement.

For the sake of clarity, although not in any limiting sense, reference is made in the following to a front chassis part or front chassis end to which the excavating device is mounted, and also to a rear chassis part or rear chassis end.

It will be understood that the part of the chassis referred to as the front part and the rear part thereof can alternate

depending on the direction in which the machine moves.

BACKGROUND OF THE INVENTION Various types of working machines that are equipped with or able to coact with one or two wheel assemblies that are adapted to run on railroad tracks and carried by a frame arrangement are known to the art.

References are made to the content of the patent publication US-A-3 263 628 for an example of such working machines.

According to one known tractor adapted embodiment, a wheel assembly that is adapted to run on railroad tracks is attached to a respective support leg via its frame arrangement, and then in an orientation along respective support legs such that when the wheel assembly is located in a lower supportive position, the horizontal distance between the wheels must be adapted to the horizontal distance between adjacent railroad tracks.

Because of the vertical arcuate movement of respective wheel assemblies when manoeuvring (raising or lowering) the support legs, the positioning of the wheel assemblies and the frame arrangement is critical since they will have this adapted hori- zontal distance solely in one specific position in relation to one another.

Furthermore, it will not be possible to use the support legs for the purpose for which they are intended, i. e. to support the working machine during excavating work, but are, instead, occupied in holding the wheels of said wheel assemblies against the railroad tracks with a concentrated force.

When using an arrangement such as this, practical experiences show that the arrangement not only makes adjustment to the height of the wheel assemblies difficult to achieve but even impossible.

It will be noted that at the same time as the horizontal dis- tance between the wheel assemblies is adjusted the wheels or tires of the working machine must be in good, adapted abutment with the rails, so as to enable the working machine to be driven forwards and backwards.

Furthermore, the loads exerted by the wheel assemblies are liable to exert an inwardly or outwardly acting force on adjacent railroad sections.

It is also known to use for the aforesaid tractor adapted purpose a carriage that carries a frame arrangement on which front and rear wheel assemblies are mounted. The carriage is constructed so that the two wheel assemblies are able to run in pairs along the mutually parallel rails of the railroad sections and the frame arrangement is dimensioned with an upper support surface. The front part of the working machine is raised by means of the excavating device or the support legs, and the carriage can be moved in under the working machine in this raised position of the front machine-part, whereafter the machine is lowered so that a chassis-section adjacent the excavating device rests on the support surface on said carriage.

The carriage is normally placed in the proximity of the place where the excavating device is attached to the chassis, and the height of the working machine above respective railroad sec- tions can be adjusted with the aid of sole plates or like devices, so as to bring the wheels and tires of the working machine into effective abutment with the respective rails of said track section.

A reduction in the thickness of the sole plates results in higher surface pressure between the wheels and tires of the working machine and the rails of the track section. A corre- sponding adjustment can be made to compensate for tire wear,

and vice versa.

The first-mentioned known tractor adapted embodiment, however, has the advantage of enabling a working machine with which wheel assemblies are mounted on the support legs to move quickly and easily to and from the working site along the track.

SUMMARY OF THE INVENTION TECHNICAL PROBLEMS When taking into consideration the technical deliberations that a person skilled in this particular art must make in order to provide a solution to one or more technical problems that are encountered, it will be seen on the one hand it is necessary initially to realize the measures and/or the sequence of mea- sures that must be undertaken to this end, and on the other hand to realize which means is/are required in solving one or more of said problems. On this basis, it will be evident that the technical problems listed below are highly relevant to the development of the present invention.

When considering the present standpoint of techniques as described above, it will be evident that a technical problem resides in providing conditions which will enable a working machine, with one or several mounted wheel assemblies, to move quickly and easily between working sites along sections of railroad tracks, and also conditions for pronounced vertical loading of the working machine in relation to the rail sec- tions, and to enable the support legs to be freely manoeuvred.

Another technical problem is one of enabling a frame arrange- ment carrying the wheel assemblies to be readily fitted to and readily removed from the chassis of the working machine in the proximity of an attached excavating device, with the aid of simple means.

Another technical problem is one of providing a relationship between a frame arrangement and a wheel assembly firmly mounted thereon which will enable the tires of the working machine to be given a predetermined pressure against underlying, mutually parallel rails of a railroad track, with the aid of simple means.

Another technical problem is one of providing mutual coaction between a raisable and lowerable frame arrangement and a wheel assembly firmly mounted thereon such that the wheels of said wheel assembly will rest on the mutually parallel rails of said railroad track with pronounced, vertically acting forces, and such that the excavating device can move freely, and such that the support legs are freely movable and can be used freely on both sides of the rail line sections when said frame arrange- ment is fixed relative to the working machine, and thereby enable respective wheel assemblies to be actuated by an own piston-cylinder device so as to enable said wheel assemblies to be quickly raised out of coaction with said rail section and therewith allow the working machine to be moved easily and simply from one working site along one section of track to a working site further along said track, and where the wheel assemblies can be manoeuvred (raised and lowered) from the driver's cabin.

It will also be seen that a technical problem is one of rea- lizing the significance of fixing the frame arrangement in relation to the pivot shafts of the support legs, so as to simplify attachment and removal of the frame arrangement.

It will also be seen that a technical problem is one of reali- zing the significance of causing a horizontally positioned pivot shaft to pivotally connect the frame arrangement with said wheel assembly, and providing a piston-cylinder device that acts between the frame arrangement and the wheel assembly so as to enable the wheels to be raised from an underlying

track section or lowered forcibly thereonto.

It will also be seen that a technical problem resides in reali- zing the significance of providing a wheel assembly that includes a transverse rod or shaft that has mutually parallel arms attached thereto.

Another technical problem is one of realizing the significance of mounting the wheels on the ends of the transverse rod, and particularly of mounting pairs of wheels or boggy-type wheels rotatably on said ends of said transverse rod.

Another technical problem is one of realizing the significance of attaching the frame arrangement to the chassis via a trans- verse shaft that is positioned forwardly of the pivot shafts of the support legs.

Still another technical problem is one of realizing the signi- ficance of and the advantages that are afforded by adapting the piston-cylinder device for action between an attachment point that is positioned adjacent to and above said horizontal pivot shaft and an attachment point on or adjacent to the transverse rod, preferably adjacent the ends of said rod.

Another technical problem is one of constructing a lightweight frame arrangement that will withstand occurrent forces and that can be fitted to and removed from the chassis solely with the aid of bolts that coact with bearing blocks.

SOLUTION With the intention of solving one or more of the aforesaid technical problems, the present invention takes as its starting point a working machine which is fitted with a wheel assembly whose wheels are adapted to run on railroad lines and which is of the kind defined in the introduction. More particularly, the invention relates to a frame arrangement that is fixed in

relation to support-leg pivot shafts, wherewith a horizontally positioned pivot shaft interconnects the frame arrangement and said wheel assembly, and wherewith a piston-cylinder device acts between the frame arrangement and the wheel assembly so as to enable the wheels to be raised from an underlying railroad track section and lowered onto said section with an adapted force.

According to proposed embodiments that lie within the scope of the inventive concept, the wheel assembly includes a transverse rod or shaft and arms attached to said rod or shaft.

Furthermore, the wheels shall be attached to the end of the transverse rod. One wheel pair will preferably be rotatably mounted on said ends of said transverse rod.

According to one embodiment of the invention, the arrangement is attached to the chassis via a transverse shaft that is positioned forwardly of the support leg pivot shafts.

The piston-cylinder device is adapted to act between an attach- ment point positioned adjacent to and above said horizontal pivot shaft and an attachment point on or adjacent to said transverse rod.

According to one embodiment, the frame arrangement includes two plates and, when applicable, a peripherally orientated edge plate.

A support arrangement will ideally extend from an upper plate.

In addition, the invention includes the provision of support- leg bearing blocks and extended shafts that are attached to one or more plates through the medium of holes provided therein, the diameters of said holes exceeding the diameter of the bolts or like fasteners used so as to provide an adjustment facility.

ADVANTAGES Those advantages primarily characteristic of a tractor adapted working machine on which there is mounted a wheel assembly which is adapted to run on railway lines in accordance with the present invention reside in the ability to pivotally couple the frame arrangement to said wheel assembly such that the excavating device will be free to carry out its functions, such that the support legs can be adjusted freely to desired supportive coaction with an underlying support, and such that two shafts related to said support legs can be positioned to also function as attachment points for the frame arrangement.

Another advantage is that the present invention is that the working machine can be moved from and to respective rail sec- tions much more easily than in the case of known machines of this kind, insomuch that the wheel assemblies can be raised and lowered by means of an own hydraulically operable piston- cylinder device that can be operated from the driver's cabin.

The main characteristic features of an inventive working machine to which there is fitted a wheel assembly whose wheels are adapted to run on railroad lines will be evident from the characterizing clause of the following Claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail with refe- rence to a currently preferred tractor adapted embodiment of a working machine having fitted thereto railroad-adapted wheel assemblies with associated frame arrangements, and also with reference to the accompanying drawings, in which

Figure 1 illustrates in perspective a working machine that has a front and a rear rail-adapted wheel assembly whose wheels support against and coact with mutu- ally parallel, underlying lines; Figure 2 is a perspective view of one firm attachment of the frame arrangement to the chassis of the working machine; Figure 3 is another perspective view of the attachment of the frame arrangement to the chassis according to Figure 2; Figure 4 is a view of the frame arrangement from above, with no bearing blocks fitted; Figure 5 is a side view of the front part of the frame arrangement according to Figure 4; Figure 6 is a side view of the attachment of the wheel assembly to the chassis from the other side in relation to Figure 1 and shows a part of said attachment in an enlarged view; and Figure 7 illustrates the wheel assembly and its frame arrangement from above.

DETAILED DESCRIPTION OF EMBODIMENTS AT PRESENT PREFERRED Figure 1 is a perspective view of a working machine having a chassis 2 that includes a front part 2a and a rear part 2b.

The working machine 1 coacts with two wheel assemblies adapted to run on railroad tracks or lines, i. e. a front wheel assembly 3 and a rear wheel assembly 4.

The present invention relates primarily to the front wheel

assembly 3, and consequently only this wheel assembly will be described hereinafter.

The rear wheel assembly 4 is of simple construction and is fastened to the working implement attachment 2c on the working machine by means of an implement locking means.

The rear wheel assembly 4 includes a transverse rod or shaft. A rail-adapted wheel is fitted on a respective end part of said transverse rod or shaft.

The wheel assembly 4 can be typically raised with the aid of a piston-cylinder device 2d belonging to the working machine.

The working machine 1 includes an excavating device 5, or digger, of known kind mounted on the front part 2a of the working machine 1, and two side-related support legs 6,6a located adjacent the excavating device 5 relative to the longitudinal direction of the chassis.

Each support leg 6,6a is pivotally mounted on the chassis part 2a via a respective pivot shaft 7,7a, and can be raised and lowered by means of a piston-cylinder device 7'belonging to the working machine.

The front wheel assembly 3 is carried by a frame arrangement 8 which is fixed in relation to each of said support-leg pivot shafts 7,7a through the medium of sleeves 8a, 8b in the form of bearing blocks fitted to the frame arrangement. (The sleeve 8b is hidden in the Figures).

The pivotal frame arrangement 8 and the wheel assembly 3 are mutually interconnected by a pivot shaft 9, and one or two piston-cylinder devices 10,11 acts, act, between the frame arrangement 8 and the wheel assembly 3 for raising said wheel assembly, or wheel pair 3a, 3b (and opposing wheel pairs 3a', 3b') from an underlying rail section 13,13a or lowering said

wheel pair onto said rail section.

These piston-cylinder devices 10,11 are designed to enable the front chassis part 2a of the working machine to be forcibly raised and therewith adjust the machine tire pressure against the railroad section 13,13a.

The wheel assembly 3 includes a transverse rod, tube or shaft 3c and arms 3d attached thereto. (The arm 3d'is hidden in Figures 1 and 2).

The wheel pairs 3a, 3b, 3a', 3b'are fitted on the ends of respective transverse rods 3c. Figure 1 shows two wheels rotatably mounted on the ends of said transverse rod and mutually coupled in the manner of a boggy assembly.

The frame arrangement 8 is attached to the chassis 3 by means of a transverse shaft 8d or the like positioned forwardly of the support-leg related shafts 7,7a.

The piston-cylinder devices 10,11 are adapted to act between an individual attachment point lOa (lla) positioned above said horizontal pivot shaft 9 and an attachment point lOb (llb) on or adjacent to said transverse rod 3c.

Figures 4 and 5 illustrate a proposed frame arrangement 8 which includes an upper flat plate 81 and a lower flat plate 82 and at least one peripheral edge plate 83. A support device 84 that forms the attachment lOa and lla extends over the plate 81.

Figure 4 does not show the bearing blocks 8a, 8a'for coaction with the end parts of extended shafts 7,7a, although it does show the provision of holes in the plate 81 for receiving bolts that coact with these bearing blocks. The holes have a diameter which is greater than the diameter of the bolts, so as to enable the bearing blocks to be adjusted to the extended shaft 7.

This also applies to the holes for the bearing blocks 8b, 8b' and the holes for the bearing block for the front shaft 8d.

It will be noted that the entire wheel assembly 3 and frame arrangement 8 can be fitted and removed by attaching and loosening the bearing blocks via the bolts.

Figure 6 is a side view of the attachment of the wheel assembly 3 to the chassis from the other side in relation to Figure 1, and Figure 7 shows the wheel assembly and the frame arrangement 8 from above, where components have been designated the same reference signs as those used in the preceding Figures.

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