The present invention relates to a ski track maintenance machine defined in the introductory section of the appended patent claim, for making a ski trail in snow or for maintaining a ski trail covered by snow.

In the prior art there are known ski track maintenance machines including a crushing device for loosening the snow and a successive trackmaking machine for making a pair of tracks in the loosened snow, and the said ski track maintenance machines are pulled by using suitable tractor means.

A drawback with the known ski track main¬ tenance machine is that the crushing device generally is so wide, that it loosens the whole ski trail at a given depth. This depth is normally defined by the deepest points of the ski trail, particularly the depth of the track grooves. Thus the loosening depth may be relatively large, i.e. 5 - 10 cm. Consequently the crushing device must be very efficient in order to achieve the required loosening depth. Accordingly, the crushing device needs a lot of power in operation, and it must be relatively heavy in construction. Moreover, the handling of such a heavy-built crushing device is cumbersome.

The object of the invention is to introduce a novel ski track maintenance machine whereby the above described drawbacks can be avoided.

The apparatus of the invention is characteri- zed by the novel features enlisted in the appended patent claim.

An advantage of the invention is that the crushing device includes two separate units, the first of which is now used to cutting the ski trail along its whole width to a suitable depth for free skiing, and the second of which is used for cutting the traditional track bases to a depth somewhat deeper than in the free

skiing trail, to the effect that both the free skiing trail and the traditional track are properly main¬ tained.

Another advantage of the invention is that the division of the crushing device into two separate units saves energy, because it is not necessary to cut the whole ski trail to the depth of the traditional track.

Yet another advantage of the invention is that the adjustment range of the machine of the present invention is better than in the prior art machines, which also leads to better results, i.e. a better main¬ tained ski trail.

The invention is explained in more detail below, with reference to the appended drawings, where figure 1 illustrates a ski track maintenance machine of the present invention, seen from the top; figure 2 illustrates the machine of figure 1, seen from the side; and figure 3 illustrates a crusher tool unit of the second crushing device unit, seen from the top.

The ski track maintenance machine of the invention is schematically illustrated in figure 1. It comprises a crushing device 1 for loosening the snow and a trackmaking device 2 for making a pair of tracks a, b in the loosened snow. The ski track maintenance machine is pulled by a suitable tractor device (not illustrated in the drawing) at a hauling beam 3 to the direction A. The crushing device 1 is compiled of two units 4, 5. The first unit 4 is a general crusher, provided with a wide crusher tool unit 6, for loosening the snow surface of the ski trail. The second crushing device unit 5 is a track base crusher, provided with two parallel crusher tool units 7, 8 spaced at a dis¬ tance r, for loosening the bottom grooves of the pair of tracks.

The trackmaking device 2 comprises means 9 for making the track grooves a, b and a pressure plate 10, on top of which there is advantageously located a motor 11 (illustrated with dotted lines in figure 1). In the first frame structure 12 of the unit 4 of the crushing device 1, there is fitted a crusher tool unit 6 rotating around an axis 13 transversal to the proceeding direction of the machine, the said crusher tool unit 6 including disc-like cutters 14 which are suitably spaced on the axis 13. At the front of the frame 12, there are arranged hauling beams 3 in order to secure the ski track maintenance machine to the tractor device. In addition to this, the crusher tool unit 6 is provided with a protecting cover 37. The second crushing device unit 5 comprises a frame 15, which is formed of two parts: a first frame section 16 and a second frame section 17, which are vertically adjustable with respect to each other. At the front of the first frame section 16 there is secu- red a hauling beam 18, whereby the second crushing device unit 5 and the trackmaking device 2 are connec¬ ted to the rear of the first crushing device unit 4.

In the first frame section 16, in between its side beams 16a, 16b, there are fitted two parallel crusher tool units 7, 8. In this embodiment they are realized by means of disc-like cutters 20, 21 arranged on an axis 19 at a distance r from each other. The power transmission means of the disc-like cutters 20, 21 are advantageously located on the axis 19, and the actuator proper, such as a hydraulic motor, is located for example at the other end of the axis 19. Moreover, the disc-like cutters 20, 21 are advantageously arran¬ ged on the axis 19 so that they can be shifted, in the direction of the axis, by using transmission means 25a, 25b, such as hydraulic cylinders, thus adjusting the mutual distance r of the cutters 20, 21. The crusher tool units 7, 8 are also provided with a protective

cover 38.

The first frame section 16 and second frame section 17 of the frame 15 are turnably secured to each other by means of pins 22, 23. In between the two frame sections 16, 17 there is fitted an adjusting device, such as a hydraulic cylinder 24, in order to adjust the mutual distance of the frame sections 16, 17. By means of this adjustment of distance, the loosening depth b of the crusher tool units 7, 8 of the second crushing device unit is set to be suitable.

The trackmaking device 2 is arranged at the end of the second crushing device unit 5. The pressure plate 10 and the means 9 for making the track grooves are advantageously secured in between the side beams of the second frame section 17 of the frame 15. On top of the plate 10, there is installed a motor 11, which provides the necessary hydraulic pressure for the sepa¬ rate hydraulic motors, and hydraulic cylinders, which are used both in the crushing device and in the track- making device for running the various members thereof. To the members 9 for making the track grooves there are advantageously connected transmission means 26, such as hydraulic cylinders. By using the transmis¬ sion means 26, the members 9 can be moved transversally with respect to the proceeding direction, and thus the mutual distance s of the track grooves a, b can be adjusted. The transmission means 26 or the members 9 and the transmission means 25a, 25b of the disc-like cutters 20, 21 of the second crushing device unit 5 are advantageously coupled so that they can be adjusted simultaneously, and so that both the mutual distance s of the members 9 and the mutual distance r of the dis¬ c-like cutters 20, 21 remains equal, i.e. s = r. Thus the bottoms of the track grooves a, b can be cut at a desired depth b, and deeper than with the cutters 14 of the first crushing device unit 4 (cf. figure 2).

The crusher tool units 7, 8 of the second

crushing device unit 5 are advantageously realized according to figure 3. In this embodiment, both crusher tool units 7, 8 comprise two successively installed disc-like cutters 27, 28 and 29, 30. Now the crusher tools are arranged in connection with two axes 31, 32. By intermediation of the said axes, the running power is transmitted to the cutters 27, 28 and 29, 30. More¬ over, the said cutters are most advantageously instal¬ led on the axes so that their distance can be adjusted for instance by means of cylinders 33, 34 and by power transmission means 35, 36 connected thereto.

The ski track maintenance machine of the present invention is operated as follows. The ski track maintenance machine is attached to a suitable tractor device at the hauling beam 3 of the first crushing device 1. The second crushing device unit 5 and the trackmaking device 2 connected thereto are in turn fastened, at the hauling beam 18, to the rear of the first crushing device unit 4, in connection with the frame 12 thereof. The running power for the first crushing device unit 4 can be taken either from the tractor device or from the motor 11 of the second crushing device unit 5. Whe pulling the ski track main¬ tenance machine with the tractor device, the first crushing device unit 4 loosens the ski trail at the first depth a, which generally corresponds to a desired light treatment of a track base suited to free skiing. The second crushing device unit 5 is set to pass along the track arranged in the ski trail, so that the crusher tool units 7, 8 of the second crushing device unit 5 follow the track grooves and loosen them at the second set depth b (cf. figure 2). The members 9 of the trackmaking device follow the crusher tools 7, 8 of the second crushing device unit 5 at a standard distance s from each other and compact the freshly loosened snow to new track grooves a, b. When necessary, for instance in downhill slides and turns, the mutual distance s of

the track grooves a, b can be adjusted, as well as the distance of the crusher tool units 7, 8 and the distan¬ ce r of the members 9 respectively.