The present invention relates to a rail-track of the general kind being built up of sections consisting of pairs of parallel rails being connected to each other by means of cross-ties or sleepers, and also relates to a method for producing such a rail-track.

In rail-tracks of the above indicated, general kind, which within many areas are employed for the transport of rail-cars or vehicles, the rails conventionally consist of hot-rolled rail profiles. Such hot-rolled rails have inferior accuracy to size, i.e. they are far from straight and bend considerably along a normal rail-section. When laying out and assembling such a rail- track it is accordingly essential to straighten each rail-section by forcing it by means of a spit or by pressing by means of jacks. Within many ranges of application where the rail is only intended to transport a rail-carriage without any requirement for higher accuracy, such a straightening by means of a spit or a jack is quite sufficient in order to ensure that the carriages may be transported thereon without any problem, especially since the carriages in such cases often are guided only at one of the rails and is solely supported on the other rail.

By such rail-tracks which are employed for instance within the engineering industry for transporting workpieces clamped in fixtures or on pallets, from a storage to a processing machine, a conventional rail-track constructed of hot-rolled rails does however impart a heavy restriction on the possibilities of the system, especially due to the poor accuracy of the rail-track. Specifically, carriages or trucks supported on rails and having fork lift systems, for instance high stacking machines in combi- nation with high storage systems, are used in such connections, and by means of said carriages or trucks workpieces are lifted down from storage shelves and are transported on the rail-track to processing machines for processing therein.

Due to the poor accuracy of the rail-track itself - practially it is not possible to achieve a greater accuracy than 10 mm - it is not possible to position the workpiece directly into the

processing machine by means of the rail-carriage or industrial rail-truck, but instead a workpiece changer apparatus or work¬ piece transfer station will have to be provided at each pro¬ cessing machine in order to position the workpieces received from the rail-carriage in the processing machine with the required accuracy. On the whole this limitation also results in a poor flexibility, since the entire factory or workshop must be adapted for a specific system from the very beginning and cannot, without great efforts and costs subsequently be supplemented with optio- nal structural solutions as the operation is automized or is expanded.

The basic object of the present invention is therefore to provide a rail or rail-track of the kind indicated in the introduction, by means of which the above discussed shortcomings and limita¬ tions of the prior art rail-tracks of this kind may be elimina¬ ted.

According to the invention this object is achieved by means of rail-track of the kind indicated in the enclosed patent claim 1, whereby the dependent subclaims 2-5 indicate preferred embodi¬ ments of the rail-track indicated in claim 1. Patent claim 6 indicates a method for producing the rail-track according to the invention, whereby the dependent subclaims 7-10 indicate pre- ferred embodiments of the method indicated in claim 6.

The invention and its principles will be described more closely below with reference to an embodiment thereof which, serving as an example, is illustrated in the enclosed drawings, on which:

Fig. 1 is a perspective view from above of a section of the rail-track according to the invention,

Fig. 2 is an elevational view from above of a rail-section according to Fig. 1 and of portions of sections con¬ nected thereto,

Fig. 3 is a side view of a rail included in the rail-section according to Figs. 1 and 2,

Fig. 4 is a side view of a sleeper included in the rail accor- ding to the invention,

Fig. 5 is an elevation from above of the sleeper according to Fig. 4,

Figs. 6a and 6b are partial side views of an end region of the sleeper according to Fig. 4, with the corresponding rail of the rail-track in a loosely laid out and firmly assembled condition respectively, and

Fig. 7 is a schematic illustration of the rail-track according to the invention laid out in a workshop.

The rail or rail-track according to the invention is assembled from separate sections 1, as illustrated in Figs. 1 and 2, which each in the conventional way consist of two rails 2 which are connected to and are maintained at a predetermined distance from each other by means of a number of sleepers 3.

The basic feature necessary for achieving the accuracy being the object of the present invention is that, contrary to the conven¬ tional rail-track, the rails consist of ground shafts or axles having very high accuracy to size, i.e. they are completely straight and have exactly the same cross-sectional profile along the complete length thereof. It is not of absolutely crucial importance for the invention to employ shafts or axles having a cylindrical cross-section, but ground bars having another rounded cross-sectional profile are also possible to use within the scope of the present invention, provided that they may be manufactured with the same accuracy. However, ground shafts having cylindri- cal cross-section are primarily used, especially for reasons of cost, in view of the fact that they facilitate the production as well as the assembly.

The two rails 2 of each rail-section 1 are cut to exactly the same length and are provided with diagonal through-bores 4 distributed in groups or sets along the length of the rails 2, at the positions of the sleepers 3 to be connected to the rails 2. In the illustrated embodiment the holes 4 are provided in sets of two for each end of the respective sleeper 3, with the excep¬ tion that only one hole 4 is provided at the respective end of the rails, i.e., as is illustrated in Fig. 2, one sleeper 3 will be provided at the joint between ad acent sections 1, with the two mounting holes at the respective end of the sleeper provided at the respective end of the adjacent rails 2. Naturally, the invention is not restricted to this specific embodiment, but also comprises such variations as different distances between the sleepers and different numbers of holes 4 for the respective ends of each sleeper. Likewise, it is not necessary to provide a sleeper 3 precisely at the joint between two sections, although this configuration is preferred. Another simplified configuration is that each section 1 is terminated by one sleeper 3 at both ends.

An essential characteristic of the invention, making it possible to achieve the high accuracy, is that the holes 4 are drilled with the same accuracy and above all in the identical position in the two rails 2 of the respective section 1. Therefore, it is a characteristic of the method according to the invention to arrange the two rails 2 of the same section 1 alongside each other in a fixture and to drill the holes 4 of said two rails 2 simultaneously in one and the same machine. The result of this is that the rails 2, which have been cut to exactly the same length, may be provided with identically positioned mounting holes 4. Due to the fact that the holes 4 in themselves are drilled with such an accuracy and having such a cross-sectional dimension that the shafts of the bolts 5 connecting the rails 2 to the sleepers 3 in principle form a sucking fit with the holes 4, it is quite easily possible to achieve an accuracy for the rail according to the invention of approximately 0,1 mm, i.e. with respect to the position deviation for a workpiece changer

or the like supported on the rail, when the changer is posi¬ tioning a fixture in a processing machine.

Regarding the positioning of the mounting holes 4 in the rails 2, it should be clarified that is is of the greatest importance for the accuracy of the complete rail, that the mounting holes 4, as mentioned above, are identically positioned in the two rails 2 forming the same section and being cut to exactly the same length, that the mutual distance between the mounting holes 4 in the respective set or group is precise and the same for the different sets or groups and that the single mounting holes at each end of the rails 2 are drilled at an exact distance from the corresponding rail end, said last-mentioned distance, in the illustrated embodiment of two mounting holes 4 in each set or group, corresponding to half the mutual distance between the holes of the sets or groups. On the other hand the distance between the respective sets or groups of mounting holes 4 is of less importance, i.e. provided that the sets or groups are identically positioned on the two rails 2 the distance between the separate groups may vary without lowering the accuracy of the actual rail-track.

Referring to Fig. 3, it is illustrated that a recess 4a is pro¬ vided at the upper end of the bore 9, for receiving the head of the bolt 5, although this is not absolutely necessary since the rail 2 consisting of the ground shaft makes it possible to support a carriage or workpiece changer on the rail-track by means of wheels supported on the sides of the rails 2 and not on top thereof; said possibility not being illustrated in the drawings. The above-mentioned possibility is above all advan¬ tageous due to the fact that there is no risk of the accuracy being lowered due to dirt gathering on the upper side of the rail.

Figs. 4 and 5 illustrate an example of a sleeper 3 to be employed for connecting the rails 2. As illustrated the sleeper 3 does, seen in the elevational view from above, have a conventional rec-

tangular shape - although the precise outer shape illustrated for the sleeper is not crucial for the invention - and each sleeper 3 is provided with a transverse, milled groove 6 adjacent each short side thereof. For the purpose of lowering the costs the sleeper 3 is manufactured from a blank of rolled iron which has been cut to the desired length. The rolled blank does not present any accuracy to size in itself, but the accuracy required for the rail-track is achieved by means of the processing of the cut blank in a controlled processing machine. By the milling of a groove 6 in the controlled processing machine it is possible to achieve an accuracy at least corresponding to that of the ground axle or shaft, at least as regards the parallelism of the grooves 6, the distance between the centers of the two grooves 6 of each sleeper 3 as well as the width B and depth D of the grooves. The same is true for the two threaded bores 7 drilled in the bottom of the grooves 6 and intended for receiving the mounting bolts

5 by means of which the rails 2 and the sleepers 3 are connected to each other. The distance between the centers of the mounting holes 7 as well as their positioning in the groove 6 is therefore very exact and does in fact present the same accuracy as that of the mounting holes 4 in the rails 2.

The two transversal grooves 6 in the sleeper 3 are intended for receiving the lowermost portion of the respective rail 2 of the section 1 therein, and in order to provide for a stabilizing of the rail 2 in the respective groove 6 the grooves are provided with sharp corners or edges 6a, 6b at their upper side edges and the relationship between the depth D and width B of the groove

6 is adapted in such a manner to the diameter of the rails 2 that the rails, when these are loosely positioned in the grooves, rest on the sharp corners 6a, 6b but do not contact the bottom 6c of the grooves 6. This configuration means that when the mounting bolts 5 are tightened the sharp corners 6a, 6b will be deformed - depending upon the choice of material the sharp corners may possibly also be forced somewhat into the ground axle 2 - until the rail engages the bottom 6c of the groove 6, whereby a firm support for the rail 2 in the groove 6 is achieved. This confi-

guration also provides for a possibility of taking up inaccuraci¬ es of the grooves by the deformation, in the case where these are formed having less accuracy. From the above it is clear that it is necessary for achieving the above described effect to be able to determine an exact or precise relationship between the depth D and width B of the groove. Due to the fact that the sleeper 3 is manufactured from a blank having lower accuracy to size it is necessary to mill a reference surface 6d i connection with the groove 6, whereby the depth D of the groove 6 is determined from this reference surface 6d.

As is especially clear from Fig. 4 the sleeper 3 is also provided with a chamfer 8 at the respective short side thereof, and the purpose of this chamfer 8 is that it shall provide support for a support wheel, not illustrated in the drawings, of the carriage or the like which is intended to run on the rail-track. This support wheel will engage the rail 2 from the side and from below and will run obliquely on its underside and will thereby stabilize the carriage on the rail-track, i.e. it will prevent the carriage from tilting or overturning towards any side when loaded unevenly.

The above described stabilization of the rail 2 in the groove 6 of the sleeper 3 is illustrated with specific reference to Figs. 6a and 6b where Fig. 6a illustrates the rail 2 loosely laid out in the groove 6, i.e. resting on the sharp corners 6a, 6b of the groove, at a distance from the bottom 6c of the groove. Accordingly, this is the initial position when mounting the rails to the sleepers, where the rails have been positioned or laid out in the grooves and the mounting bolts 5 have been inserted through the holes 4 and have been engaged in the mounting holes 7 by hand. Subsequent to this first manual tightening of the mounting bolts the rails are straightened in the grooves where¬ upon the mounting bolts 5 are tightened fully so that the sharp corners 6a, 6b are deformed - and are possibly partly forced into the rail 2 - until the rail engages the bottom of the groove, as illustrated in Fig. 6b.

Figs. 4 and 5 further illustrate that the sleeper 3 is provided with four threaded bores 9 of which two are provided just inside each groove 6 of the sleeper 3 and at a distance from each other in the transversal direction of the sleeper. These threaded bores 9 are intended for receiving adjustment screws by means of which each sleeper 3 is adjusted to a completely level position, independent of irregularities of the ground or bedding, with the aid of a machine level or the like. Furthermore each sleeper 3 is provided with a number, in the illustrated embodiment four, holes 10 provided at suitable locations in the sleeper 3 and intended for receiving expansion bolts by means of which the sleeper 3, and accordingly the complete rail-track, are fixed to the ground or bedding, such as a workshop floor or the like, after the adjustment carried out by means of the adjusting screws. Finally two holes 17 are provided substantially in the middle of the sleeper and separated in its longitudinal direc¬ tion. These holes 17 are intended for the attachment of a, not illustrated, position stop for a carriage or the like running on the rail-track.

As a result of the described measures and configurations accor¬ ding to the invention a precision rail-track is obtained which may be produced with such minor deviations that it may be directly employed for moving a workpiece changer thereon, which in turn directly positions a workpiece in a processing machine. An example of a configuration intended for such use is given below.

For the rails is employed a ground shaft or axle of steel SIS 1650 having a diameter of 70 h 10, which is cut in sections of 6 meters with an accuracy of ±0,1 mm. In the two rails being simultaneously drilled for each section, the outer, single mounting holes are drilled at a distance (with reference to their centers) of 50 mm from the respective end of the rails and with an accuracy of +0,05 mm. In the rails there are furthermore drilled nine sets or groups of two mounting holes each, whereby the distance between the centers of the mounting holes in the

respective set or group is 100 mm with an accuracy of ±0,05 mm. The distance between the respective sets or groups, measured from the center of the outer holes in the respective set or group, is 500 mm, whereby the accuracy in the present case is ±0,05 mm although this measure, as has been mentioned above, is not criti¬ cal for the accuracy of the complete rail-track. For achieving the mentioned sucking fit the holes 4 of the rails are drilled to a diameter of 16,1 mm for mounting bolts Ml6.

In this case sleepers are employed, manufactured from a blank of rolled iron, for instance SIS 1312, having a width of 200 mm, said blank having been cut to a length of 1789 mm. The grooves 6 at the respective short side of the sleeper 3 are milled exact¬ ly parallel and with a distance from center to center of 1709 mm and having an accuracy of ±0,05 mm. The grooves 6 are in them¬ selves milled having a width of 30 mm and a depth of 4 mm, measured from the reference surface 6d, both with an accuracy of ±0,05 mm. In this case the reference surface 6d is milled to a depth of 1 mm, but this measure is less important since the main point is only to provide a surface from which the depth of the groove 6 may be precisely or exactly determined. In the milled grooves 6 the mounting holes 7 are drilled with a distance from center to center of 100 mm and with an accuracy of ±0,05 mm. For the sake of completeness it should also be mentioned that the chamfer 8 in this case forms an angle of 45° with the bottom of the groove and that the blank, from which the sleeper 3 is manu¬ factured, has a thickness of 30 mm.

With the above described configuration a total accuracy for the rail-track better than 0,1 mm is achieved, i.e. a maximum devia¬ tion of 0,1 mm can be achieved for a workpiece changer advanced on the rail-track, this measure referring to the positioning of a fixture in a processing machine.

Fig. 7 finally illustrates an example of an application of the rail-track according to the invention in workshop. In this case the rail-track 16 is laid out alongside a storage 11 which may

be a fixture stand or the like. On the rail-track runs a travelling carriage 12 which in turn supports a workpiece changer 13 which serves one or more processing machines, preferably machining centers 14, 15. With the accuracy of the rail-track 16 achieved by means of the present invention it is therefore possible to perform a controlled movement of the workpiece changer 13 supported on the travelling carriage 12 along the rail in order to fetch fixtures 16 from the fixture stand 11, said fixtures being directly positioned in the desired machining center 14, 15 after a renewed, controlled movement along the rail. Through the accuracy achieved in accordance with the present invention it is therefore possible to do without a sepa¬ rate, stationary workpiece changer at each processing machine. This in turn means that the system is very flexible. With such an accuracy of the rail-track the travelling carriage may also without any problem be moved with a relatively high speed.

Although the invention has been described herein with specific reference to a preferred embodiment thereof, the invention shall not be restricted to this specific embodiment, but also comprises such modifications and variations thereof that are obvious to a man skilled in the art. Therefore, the invention shall only be restricted by the enclosed patent claims.