Power transmission of a turning-track track-laying vehicle

The invention relates to a power transmission of a turning-track track-laying vehicle. 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 the track belt.

BACKGROUND OF THE INVENTION 
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 which 
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. 
SUMMARY OF THE INVENTION 
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, 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 and 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.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The turning-track vehicle shown in FIGS. 1 and 2 comprises a track belt 10, 
whose structural details are discussed for instance in the inventor's U.S. 
Pat. Nos. 3,934,664; 4,046,429; 4,119,356; 4,188,176 and Finish Pat. Nos. 
51308 and 54259. The track belt 10 is installed between the end rolls 11 
and 12. The foremost end roll 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 frame 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 arranged to 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 footsteps 25 on the both side of the seat, 
all these parts known as such. 
The vehicle comprises a motor 26, fastened to the frame section 20. A 
sprocket wheel fastened 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, 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, 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, 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 30 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. 
The traction sprocket or sprockets 30 is/are so arranged on the drive shaft 
34, that the traction sprocket or sprockets 30 can axially move to a 
position generally determined by the track belt 10. The traction sprocket 
or sprockets is/are also arranged to turn about an essentially horizontal 
or upright axis, to a position determined by the degree of curvature of 
the track belt 10. 
Another, more precise exemplary embodiment of an axially selfadjusting 
adjusting fit between the traction sprockets 30 and the shaft 34 is 
illustrated in FIGS. 4 and 5. In accordance with these figures, the 
traction sprockets 30 comprise, on their outer diameter, an annular 
section 30a, to which the traction cogs 32 are fastened. The flange 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 34 to the sleeve part 
35 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 other words, there are several axial grooves 38 provided in the drive 
shaft 34, and there are corresponding internal grooves 37 provided in a 
fastening sleeve section 35 of the traction sprocket or sprockets 30. 
Furthermore, there are balls or similar elements in these opposite grooves 
37, 38 which transmit torque from the driving shafts 34 to the traction 
sprocket or sprockets 30, and which let the traction sprockets 30 move 
axially with respect to the drive shaft 34, as illustrated in FIG. 5. 
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 measurements a 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. 
Preferably, 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, most 
preferably approximately three times the width b of the traction cog at 
the opening thereof. 
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 with the lateral movement facility 
of the traction sprocket or sprockets 30. 
Therefore, the traction sprocket or sprockets both turn about a 
substantially horizontal or upright axis and laterally move to a position 
determined by the degree of curvature of the traction belt 10. 
To summarize, the present invention is directed to power transmission of a 
turning-track, track-laying vehicle, the track-laying vehicle comprising a 
closed-loop track belt 10 arranged between end rolls or similar elements 
11, 12 in a manner such 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 27, 28, 29, 31 
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 a middle range thereof. Cogs 32 or similar 
elements are provided in the traction sprocket or sprockets 30, these cogs 
32 being in driving contact with openings, grooves, or similar apertures 
40 of the track belt, so that the traction force can be transmitted from 
the traction sprocket or sprockets 30 to the traction belt 10. 
A drive fit between an 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 interactively take 
a driving position which is principally determined by the curvature of the 
track belt. 
The various details of the invention may vary within the inventional 
concepts set forth alone.