Snow vehicle equipped with wide, low-pressure tires

Disclosed is a vehicle which is constructed to include a pair of steerable right and left front skis suspended from a front portion of a frame. Further included are a pair of right drive wheels and a pair of left drive wheels which are suspended from a rear portion of said frame and adapted to be driven by said engine. Each of the drive wheels has a wide, low-pressure tire. The front ski and rearwardly located driving wheels on each side of the frame are aligned longitudinally to achieve a base having substantially uniform width from front to back.

BACKGROUND OF THE INVENTION 
Until recently, the only vehicles suitable for travel off the road over 
snow covered terrain were traditional snowmobiles of the type having an 
endless drive track at the rear and one or more steering skis in the front 
or a so-called "snow cat" which utilizes a plurality of endless tracks 
without skis. Neither of these types of vehicles, however, is capable of 
adequate performance over clean, snow-free hard surfaces. 
More recently, three-wheeled or four-wheeled vehicles, equipped with wide 
low-pressure tires having an air pressure of about 0.1 to 0.3 kg/cm.sup.2 
have been used as both road vehicles and off-the-road vehicles. Although 
such vehicles are able to run off the road on snow surfaces, the wheels 
tend to pack and accumulate snow. As a result, the wheels receive high 
running resistances as they shear the accumulated snow, thus degrading the 
running performance during off the road runs over snow covered terrain. 
The present invention relates to a vehicle which is ideally suited for 
running both on hard surfaces and on off-the-road snow surfaces. More 
particularly, the invention is directed to a vehicle which is equipped 
with wide, low-pressure rear tires and either ski or similar tires on the 
front yielding improved running performance on soft snow surfaces as well 
as on hard surfaces. 
SUMMARY OF THE INVENTION 
A major object of the present invention is to provide a vehicle equipped 
with wide, low-pressure tires to improve running performance on snow 
covered surfaces. 
Another object of the present invention is to provide a vehicle having 
wide, low-pressure tires which has improved running performance on hard 
surfaces as well as snow covered surfaces. 
In order to achieve the above-specified objects, the vehicle according to 
the present invention comprises: an engine mounted on a frame; a pair of 
right and left steerable front skis suspended from the front portion of 
the frame; and a pair of right drive wheels and a pair of left drive 
wheels, said wheels each having wide, low-pressure tires being suspended 
from rear portions of the frame, and being driven by the engine. The 
device is built so that the front skis and the rear drive wheels on both 
sides are aligned in the longitudinal direction of the frame and the width 
of the device is relatively constant from front to back. As a result, the 
paired right and left front skis are adapted to be attached to the frame 
when operating the machine on snow surfaces, but may be removed and 
replaced with wheels when the machine is operated on firm or paved 
surfaces. 
Various advantages and features of novelty which characterize the invention 
are pointed out with particularity in the claims annexed hereto and 
forming a part hereof. However, for a better understanding of the 
invention, its advantages and objects obtained by its use, reference 
should be made to the accompanying drawings which form a further part 
hereof, and to the accompanying descriptive matter, in which there are 
illustrated and described certain preferred embodiments of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Certain terminology will be used in the following description for 
convenience and reference only and will not be limiting. The words 
"upwardly", "downwardly", "rightwardly" and "leftwardly" will refer to 
directions in the drawings to which reference is made. The words 
"inwardly" and "outwardly" will refer to directions towards and away from, 
respectively, the geometric center of the device and associated parts 
thereof. Said terminology will include the words above specifically 
mentioned, derivatives thereof, and words of similar import. 
Referring first to FIGS. 1 through 3, there is shown a longitudinally 
extending vehicle frame 1. Suspended from respective sides of the front 
portion of the frame 1 are a right front ski 2a and a left front ski 2b. 
Suspended from rear portions of frame 1 are a first pair of rear wheels 
comprised of a right wheel 3a and a left wheel 3b, and a second pair of 
rear wheels comprised of a right wheel 4a and a left wheel 4b. Each of 
these wheels are spaced in the longitudinal direction of the frame 1. 
Front ski 2a and rear wheels 3a and 4a are arranged in a straight line in 
the longitudinal direction on frame 1. Front ski 2b and rear wheels 3b and 
4b are also arranged in a straight line in the longitudinal direction on 
frame 1. As a result, the width of the vehicle's base is roughly the same 
from front to back. 
Mounted on a middle portion of the aforementioned frame 1 is an engine unit 
5. Engine unit 5 is comprised of an engine body 5a located at the front 
and a transmission portion 5b located at the rear. Above the engine unit 
5, there is mounted on the frame a two-passenger seat 7 which extends in 
the longitudinal direction of the frame. Located on the sides of engine 
unit 5 and secured to frame 1 are steps or running boards 8a and 8b. A 
steering handle 6 is also present in front of seat 7. 
The aforementioned front skis 2a and 2b are covered with front fenders 9a 
and 9b, and the rear wheels 3a, 3b, 4a and 4b are covered with rear 
fenders 10a, 10b, 11a and 11b, respectively. These fenders are constructed 
so as to be easily removable. 
The aforementioned engine unit 5 has its forward end pivotally secured to 
frame 1 by means of a pivot pin 12. Fixed to the rear portion of the 
engine unit 5 are a pair of right and left brackets 13a and 13b in which 
are respectively borne the axles 14a and 14b. Wheel 3a is journaled to the 
outer end of axle 14a and wheel 3b is likewise journaled to the outer end 
of axle 14b. The inner ends of axles 14a and 14b are connected to each 
other by means of a no-spin type differential mechanism 15. 
Transversely protruding from the back of transmission 5b is an output shaft 
16 which is operative to transmit the engine power to differential 15 
through a chain 17. The axles 14a and 14b are operative to transmit the 
power they receive through the differential mechanism 15 to the wheels. 
Suspended from the frame 1 by shock-absorbing means 18 are brackets 13a and 
13b. Shock-absorbing means 18 serve to resiliently support the rear 
portion of the engine unit 5 and the rear wheels 3a and 3b. 
Shock-absorbing means 18 is comprised of (1) a pair of right and left 
lever arms 20a and 20b which have their front ends hinged to the frame 1 
through rubber torsion pads 21a and 21b and their rear ends fixing to a 
hinge pin 31 extending in the transverse direction; and (2) a pair of 
right and left links 19a and 19b which have their upper ends hinged to the 
aformentioned hinge pin 31 and their lower ends hinged to the rear ends of 
brackets 13a and 13b. Rubber torsion pads 21a and 21b, which are best 
shown in FIG. 5, are retained by an outer square cylinder 22 and an inner 
circular cylinder 23. Square cylinder 22 is fixed on the frame 1 while 
circular cylinder 23 is keyed at 25 to the end 24a fixed in a shaft tube 
24. 
The rear wheels 4a and 4b are secured to axles 26a and 26b which are borne 
rotatably in bearings 28 at the rear ends of arms 27a and 27b. The front 
ends of arms 27a and 27b are borne rotatably on axles 14a and 14b. Power 
is transmitted to axles 26a and 26b from axles 14a and 14b through chains 
29 and 30 respectively. As a result, arms 27a and 27b can be detached 
toegether with the rear wheels 4a and 4b from the frame 1 by simply 
removing several bolts. 
Acting as a load distributor for rear wheels 4a and 4b is a leaf spring 33. 
Leaf spring 33 has its front end hinged by the hinge pin 31 of the 
shock-absorbing means 18. The middle portion of leaf spring 33 is pushed 
down by a rod 34 which is secured at one end to frame 1. The rear end of 
leaf spring 33 is thus forced to contact with the upper face of a bracket 
32 which is fixed to and rides over the rear portions of arms 27a and 27b. 
Both ends of the aformentioned rod 34 supporting the middle portion of the 
leaf spring 33 are hinged rotatably. A turnbuckle 35 is also connected to 
the middle portion of that rod 34 for changing the length of the rod 34 to 
adjust the contact pressure of the leaf spring 33 with the bracket 32. 
Front skis 2a and 2b are removably supported on right and left spindles 36a 
and 36b which are borne on the rear ends of rocking arms 37a and 37b so 
that they can rotate in a longitudinal direction. Spindles 36a and 36b act 
also as axles so that front wheels 2a' and 2b' rather than skis 2a and 2b 
can be attached as shown in FIG. 4. Rocking arms 37a and 37b also have 
their front ends hinged through rubber torsion pads 40a and 40b to the 
sides of the front portion of the frame to enable them to rock up and 
down. 
Extending obliquely forward and downward from steering handle 6 is a 
steering shaft 38. At the lower end of shaft 38 is a mechanism 39 which 
causes handle 6 and the previously mentioned spindles 36a and 36b to be 
coactive. As a result, when the handle 6 is operated to the right or left, 
the front skis 2a and 2b or the front wheels 2a' and 2b' which are 
supported by the spindles 36a and 36b are steered to the right or left 
through the steering shaft 38 and the steering mechanism 39. 
As shown in FIG. 7, the rubber torsion pad 40 hinging the front end of the 
rocking arm 37 is fixed in the same fashion as the rear side torsion pad 
21 of FIGS. 5 and 6. Square cylinder 41 fits over the outer periphery 
thereof and a circular cylinder 42 fits within the inner periphery 
thereof. Square cylinder 41 is welded to the front end of the rocking arm 
37, whereas circular cylinder 42 is keyed at 44 to a shaft tube 43 which 
extends transversely in the frame 1 and which is fixed to the frame 1 by 
means of a bolt 45. Because this bolt 45 fixes the shaft tube 43 through a 
slot 46 which is formed to extend in the peripheral direction of the frame 
1, the shock-absorbing properties of the torsion pads 40 can be adjusted 
by changing the position of bolt 45 with respect to slot 46. 
Fixed to the outer ends of the aforementioned square cylinder 41 are plates 
47a and 47b. Plates 47a and 47b are also fixed to the respective ends of a 
torsion bar 48 which extends transversely in the shaft tube 43. The 
torsion bar 48 transmits the forces loaded upon either of the right and 
left front skis 2a and 2b (or the right and left front wheels 2a' and 2b') 
from the road surface, as a torsion torque to the other, whereby the 
vehicle body is prevented from swaying excessively to the right or left. 
As has been described above, according to the present invention the paired 
right and left front skis are disposed at both sides of the front portion 
of the frame, and the paired right and left driving rear wheels are 
disposed at the backs of those front skis and arranged straight in the 
longitudinal direction of the vehicle such that the front skis and the 
driving rear wheels are made to have substantially the same width. Thus, 
the skis pack down the snow in front of the rear wheels. As a result, the 
shears of the accumulated snow by the driving rear wheels is reduced, as 
is the running resistances on snow surfaces. 
Since the paired right and left front skis can be replaceable with front 
wheels, the vehicle can be used on the paved or other hard surfaces. 
When the vehicle is equipped to run on the snow surfaces, as shown in FIG. 
3, the front skis 2a and 2b are supported on the spindles 36a and 36b 
respectively. Since skis 2a and 2b are rear wheels 3a and 3b, and 3a and 
4b are made to have substantially the same width and are arranged straight 
in the longitudinal direction of the vehicle, when the vehicle runs on a 
snow surface S, the accompanying rear wheels 3a and 3b run on that portion 
of the snow surface S which has been packed by the front skis 2a and 2b. 
See FIGS. 8 and 9. At the same time, the accompanying rear wheels 4a and 
4b run on the snow surface S which has been packed by both the skis and 
the rear wheels 3a and 3b. As a result, the driving rear wheels 3a, 3b, 4a 
and 4b accumulate less snow that needs to be sheared, thus reducing the 
running resistance. 
The present invention has great advantages over the vehicle of the prior 
art shown in FIGS. 10 and 11. The prior art vehicle's front wheel 102 and 
rear wheels 103a and 103b pack the snow surface S directly and accumulate 
large amounts of snow that needs to be sheared. As a result, the front and 
rear wheels 102 and 103 are subjected to remarkably high running 
resistances. 
When the vehicle of the present invention is equipped to run on the paved 
roads or other hard surfaces, as shown in FIG. 4, the front skis 2a and 2b 
are replaced by the front wheels 2a' and 2b'. Further, rear wheels 4a and 
4b are removed together with the rear arms 27a and 27b and the rear 
fenders 11a and 11b. Rear wheels 4a and 4b may be left in place, as shown 
at the back of FIG. 3, if more traction is required by the terrain. 
Numerous characteristics and advantages of the invention have been set 
forth in the foregoing description, together with details of structure and 
function of the invention, and novel feature thereof are pointed out in 
the appended claims. The disclosure, however, is illustrative only, and 
changes may be made in detail, especially in matters of shape, size and 
arrangement of parts, within principles of the invention, to the full 
extent indicated by the broad general meaning of the terms in which the 
appended claims are expressed.