POWER TRANSMISSION OF A TURNING-TRACK TRACK-LAYING VEHICLE

Abstract: The track-laying vehicle comprises such a closed-loop type track belt (10) arranged between end rolls or similar (11, 12) in such a way that one edge of the track belt can be stretched and the other edge of the track belt contracted in order to make the vehicle execute a turn. The vehicle comprises a motor (26), a traction sprocket or sprockets (30), and power transmission equipment between the traction sprocket or sprockets (30) and the motor (26). The drive sprocket or sprockets (30) are positioned above the top run of the track belt (10), preferably sideways in its middle range. In the traction sprocket or sprockets (30) there are drive cogs (32) or similar, which drive cogs (32) are in driving contact with the openings (40), grooves or similar of the track belt, so that the traction force can be transmitted from the traction sprocket or sprockets (30) to the track belt (10). The drive fit between the upper run of the track belt (10) and the traction sprocket or sprockets (30), such as a cog fit, is such that the fit lets the traction sprocket or sprockets (30) and the track belt (10) to interactively take such a driving position, which is mainly determined by the curvature of the track belt.

Description: Power transmission of a turning-track track-laying vehicle The present invention relates to power transmission of a turning- track track-laying vehicle, in which there is a closed-loop type track belt arranged between end rolls or similar in such a way that one edge of the track belt can be stretched and the other edge of the track belt contracted in order to make the vehicle execute a turn, which vehicle comprises a motor, a traction sprocket or sprockets, and power transmission equipment between the traction sprocket or sprockets and the motor, which drive sprocket or sprockets are positioned above the top run of the track belt, preferably sideways in its middle range, and in which traction sprocket or sprockets there are drive cogs or similar, which drive cogs are in driving contact with the openings, grooves or similar of the track belt, so that the traction force can be transmitted from the traction sprocket or sprockets to the track belt. The object of the present invention is to provide such transmission for a turning-track vehicle, by means of which the power is transmitted from a motor which is specifically located outside the track-belt loop to drive the track belt so that the track belt may be more advantageously curved than before, and that the previously noted drawbacks, which will be discussed below, can be avoided. The present invention may be used in all turning-track vehicles, either in those in which either the front end or the rear end of the track belt is forcedly controlled, or in those in which both ends are controlled by stretching one side of the track belt and by contracting the other edge in a similar way. In the Prior Art, in turning-track vehicles, whose motor and power transmission are located outside the track belt loop, such an axially fixed traction sprocket is used which is positioned above the upper run of the track belt in its center area. In known transmission systems high lateral forces have been created to the side walls of the traction sprocket or sprockets; the forces are the higher the sharper is the bend and higher is the traction force of the vehicle. Said fixed traction sprocket or sprockets have also considerably increased the steering forces because the «tight» fit of the traction openings prevents the upper run of the track belt from adjusting itself in the position required by the turning radius of the vehicle. The object of the present invention is to eliminate all these drawbacks by means of a simple and reliable transmission arrangement. For attaining the objectives mentioned above and to be described later r the principal characteristic feature of the invention is that the drive fit between the upper run of the track belt and the traction sprocket or sprockets, such as a cog fit, is such that the fit lets the traction sprocket or sprockets and the track belt to interactively take such a driving position, which is mainly determined by the curvature of the the track belt. As, in accordance with the invention, the traction sprocket or sprockets can move in the axial direction, or when the contacting parts of the traction sprocket or sprockets and the traction point of the track belt are so fitted that the traction sprocket or sprockets and the traction belt can, at the traction point, take interactive positions substantially freely and without lateral tensions or rotate around an upright axis, the longevity and functionality of the transmission structures and the track belt will be considerably better than before, and the steering forces will be lower than before, as the upper run of the track belt is free to take lateral position also at small turning radii (sharp bends) . Such an arrangement can also be favorably used in the invention, in which for instance the rear end of the track belt and its rear end roll, near which the traction sprockets should preferably be, can freely move freely take the lateral position necessitated by the turning radius of the vehicle. In this case the rear end roll of the vehicle can be mounted with bearings to the frame section, which is mounted by vertical joints to the frame structures of the vehicle. The invention will now be described in detail, by way of examples only, with reference to the figures in the accompanying drawing, with no intention to restrict the invention to these details. Fig. 1 is a schematic side view of a snowmobile equipped with powe transmission in accordance with the invention. Fig. 2 is the horizontal section II-II in Fig. 1. Fig. 3 is the vertical section III-III in Fig. 1. Fig. 4 illustrates a section of a traction sprocket, meshing the upper run of the track belt, used in a power transmission system i accordance with the invention. Fig. 5 shows a central axial upright section of a power transmission system in accordance with the invention. The turning-track vehicle shown in Figs. 1 and 2 comprises a track belt 10, whose structural details are discussed for instance in Jorma Pohjola's Finnish patents Nos. 48814, 48815, 51307, 51308, 53685 and 54259. The track belt 10 is installed between the end rolls 11 and 12. The foremost end roll 11 is mounted with bearings to a turning frame section 13, in which there are bogie wheel units 19a supporting the front section of the bottom run of the track belt. The turning frame section 13 is connected to the frame section 20 of the vehicle with an upright joint 14. The turning frame section 13 is turned, in order to make the track belt curved for steering the vehicle, by means of steering mechanisms known as such (not shown) and by handlebars 23. The rearmost end roll 12 is mounted with bearings to the frame section 15. The f ame section 15, for its part, is mounted pivotally with an upright joint 16 to the frame section of the vehicle so that the rearmost end roll 12 can relatively freely take the position determined by the curved track belt 10. If required, the rearmost end roll 12 can also be arrangedto be turned about a joint 16 or similar by means of turning mechanisms . The vehicle illustrated in Fig. 1 comprises a body 21, a windshield 22, handlebars 23, a seat 24, and footrests 25 on the both side of the seat r all these parts known as such. The vehicle comprises a motor 26, fastened to the frame section 20. A sprocket wheel stened to the shaft of the motor drives a chain 27. Said chain 27 drives the primary shaft of the gearbox 28. The secondary shaft of the gearbox 28 drives, by means of a chain 29 and a sprocket 31, traction sprockets 30 r of which there are one, two, or several side by side on the drive shaft 34. In the figures there are two parallel traction sprockets 30. The drive shaft is mounted with bearings 36 to the casing 33 of the traction sprocket unit, which is the most clearly shown in Fig. 3. In traction sprocket or sprockets 30 there are cogs 32 meshing the traction opening rows 40 r 40' or similar grooves, slots etc., located on both sides of the lateral support area 10a of the track belt 10. In accordance with this invention, the drive fit between the traction sprocket or sprockets 30 and the track belt 10 is such that it lets the track belt substantially freely take a curved position, lateral position, and/or rotational position as required by the turning radius. Thanks to the fit in accordance with the invention, there will be no detrimental axial forces or movements applied to the traction sprocket unit, the track belt, or the power transmission equipment, which would quickly wear out the parts of the power transmission system, and possibly cause malfunction. Fig. 3 shows such an application of the invention, in which the fitting of the cogs 32 of the traction sprockets 30 and the traction openings 40 of the track belt 10 is r in the laterial direction, essentially «tight», so that when the track belt 10 moves to the side position indicated in Fig. 3 with ref. 10' and phantom lines, the traction sprockets 30 can also move on the shaft 34 to the side position 30', although the shaft 35 is installed with bearings 36 to casing 33 so that it cannot move axially, so that the traction sprocket 31 does not move in the axial direction. Another, more precise exemplary embodiment of an axially self- adjusting fit between the traction sprockets 30 and the shaft 34 i illustrated in Figs. 4 and 5. In accordance with these figures, th traction sprockets 30 comprise, on their outer diameter, an annula section 30a, to which the traction cogs 32 are fastened. The flang 30b of the traction sprockets is welded to the sleeve part 35, inside which there is for instance four axial grooves 37. In the shaft 34, there are similar grooves 38 in the corresponding positions. In the opposite grooves 37, 38 there are balls 39, which transmit torque from shaft 35 to the sleeve part 36 and further on to the traction sprockets 30. At the ends of the sleeve part 35 there are seals 36. The number of balls 39 in the grooves 37, 38 is such that the traction sprockets 30 may sufficiently move in the axial direction on the shaft 34, which is fixed in the axial direction, and, when necessary considering the lateral movement of the track belt 10, equipped with thrust bearings. In addition to or instead of the fit described above, the fit in accordance with the invention between the track belt 10 and the cogs 32 of the traction sprockets 35 can be carried out so that the traction openings 40' of the track belt 10 can be made crosswise elongated and such that they are considerably wider than the traction cogs 32 at the openings 40. In Fig. 5, this is illustrated by measuremens a, which show the free lateral moving clearance of the track belt 10 with respect to the cogs 32 of the traction sprockets 30 to each direction. In this case the traction sprockets 30 can be fastened to the shaft 34 axially fixedly, whereat said dimensioning (measurements a) of the traction openings allows the interactive lateral positioning of the traction sprockets and the track belt. The crosswise width of openings 40" can be for instance so wide that the width b of the cog 32 in the middle of the openings 40' is essentially as large as the above-mentioned dimension a. In Fig. 3 one can see the supporting roll 41 of the transmission, which is mounted with bearings on a shaft 43. The shaft 43 is fastened with flanges 42 to the frame 20. The supporting roll 41 is installed at the meshing point R (see Fig. 1) between the cogs 32 of the traction sprockets 30 and the upper run of the track belt 10 to support the track belt from underneath by means of the outer wall of the lateral support region 10a so that a sufficiently good meshing will be maintained. The supporting roll 31 may, if required, be coated with elastic surface. Such arrangements are also included within the inventional idea, in which the traction sprocket or sprockets 30 are so fitted that they and possibly their shaft are relatively free to turn about an upright shaft. This rotational freedom may alone be used for attaining the objectives of the invention, or it may be used together sith the lateral movement facility of the traction sprocket or sprockets 30. The various details of the invention may vary within the inventional idea as defined in the following claims.

Claims: Claims 1. Power transmission of a turning-track track-laying vehicle, which track-laying vehicle comprises such a closed-loop type track belt (10) arranged between end rolls or similar (11, 12) in such a way that one edge of the track belt can be stretched and the other edge of the track belt contracted in order to make the vehicle execute a turn, which vehicle comprises a motor (26) , a traction sprocket or sprockets (30), and power transmission equipment (27, 28, 29, 31) between the traction sprocket or sprockets (30) and the motor (26), which drive sprocket or sprockets (30) are positioned above the top run of the track belt (10) , preferably sideways in its middle range, and in which traction sprocket or sprockets (30) there are drive cogs (32) or similar, which drive cogs (32) are in driving contact with the openings (40) , grooves or similar of the track belt, so that the traction force can be transmitted from the traction sprocket or sprockets (30) to the track belt (10), characterized in that the drive fit between the upper run of the track belt (10) and the traction sprocket or sprockets (30), such as a cog fit, is such that the fit lets the traction sprocket or sprockets (30) and the track belt (10) to interactively take such a driving position, which is mainly determined by the curvature of the the track belt. 2. A power transmission in accordance with claim 1, characterized in that the traction sprocket or sprockets (30) .are so arranged on the drive shaft (34) that the traction sprocket or sprockets (30) can axially move to the position generally determined by the track belt (10) . 3. A power transmission in accordance with claim 1, characterized in that the traction sprocket or sprockets are arranged to turn about an essentially upright axis to a position determined by the degree of curvature of the track belt (10). 4. A power transmission in accordance with one of claims 1 to 3, characterized in that the traction sprocket or sprocets both turn about an upright axis and laterially move to the position determined by the degree of curvature of the track belt (10) . 5. A power transmission in accordance with one of claims 1 to 4, characterized in that the lateral width of the traction openings (40') in the track belt is essentially wider than the width of the traction cogs (b) 32 at the openings (40) so that the track belt (10) can move laterally with respect to the traction cogs (32) . 1 0 6. A power transmission in accordance with claim 5, characterized in that the width of the traction openings (40') of the traction belt (10) is 2 to 4 times wider than the width (b) of the traction cog, preferably approx. 3 times the width "j 5 (b) of the traction cog at the opening.. 7. A power transmission in accordance with one of claims 1 to 6, characterized in that in the drive shaft (34) there are several axial grooves (38) r and that in the fastening sleeve 0 section (35) .of the traction sprocket or sprockets (30) there are corresponding internal grooves (37) , and that in said opposite grooves (37, 38) there are balls or similar elements, which transmit torque from the driving shaft (34) to the traction sprocket or sprockets (30), and which let the traction sprockets 5 (30) move axially with respect the drive shaft (34) (Fig. 5) . 0 5

Inventors: POHJOLA JORMA, POHJOLA, JORMA
Applicants: FINNCAT AB
Application year: 1986
Main classification: B62D55
IPC codes: B62D55