Testing device for vehicle tires

A testing device for vehicle tires, especially anti-skid features situated in the vehicle tire, in which the tire to be tested is pressed against an outer circle or surface of another tire, while these two tires are rotated in opposite directions. The other tire acting as a counterpart or pair for the tire being tested is a pneumatic tire, while the tire to be tested and the other tire are disposed to be pressed against one another so that a contact surface between the two tires is substantially straight. The other tire acting as the pair or counterpart for the tire to be tested is provided with a wear surface having good wear resistance properties.

BACKGROUND OF THE INVENTION 
The present invention concerns testing means for vehicle tires and 
anti-skid means, in which a vehicle tire to be tested is pressed against 
an outer circle or circumference of another tire while rotating the tires 
in opposite directions of rotation. 
Several different apparatus are known in the prior art for testing vehicle 
tires and particularly anti-skid means placed in these tires. One such 
means of the state of the art is schematically illustrated in FIG. A1. The 
means of FIG. A1 comprises a stationary circle 2 provided with a wear 
surface, along the inner periphery of which a tire 1 to be tested is 
arranged to roll. In FIG. A2 another means of the state of the art is 
presented in which the tire 1 to be tested rolls along the outer periphery 
of a stationary circle 2. However, a significant drawback of this 
apparatus is that the tire 1 to be tested meets the circle 2 in an 
incorrect position, whereby it is not possible to simulate ordinary 
driving on a road with arrangements such as those described above. 
In addition to the apparatus illustrated in FIGS. A1 and A2, an embodiment 
is known in which the circle 2 has been arranged to be rotatable, whereby 
the speed of rotation of the tire 1 to be tested is equally increased. 
A third means of the state of the art is illustrated in FIG. A3, in which 
the tire 1 to be tested has been arranged to rotate along a circle 3 
situated horizontally, this circle being either stationary or rotating. A 
drawback of this apparatus is, in turn, that the arrangement corresponds 
to continuous curve driving, whereby driving in the direct direction 
cannot be simulated with such means. In FIG. A4, another means of the 
state of art is presented in which, in a way, is a special application of 
FIG. A2. In the design of FIG. A4, the pair or counterpart for the tire 1 
to be tested is a hard wheel, e.g. made of asphalt concrete, against which 
the tire 1 to be tested is pressed while rotating so that both the tire to 
be tested and the wheel 4 rotate. A poor feature of this design is the 
same as with the means of FIG. A2, i.e. that the tire 1 meets the wheel 4 
in an incorrect position which is not equivalent to driving on a road. 
Furthermore, additional means of the state of the art are presented in FIG. 
A5 comprising a belt roll system with an endless belt 7 carried around 
return rolls 5 and 6 and against which two tires 1a and 1b to be tested 
are urged on two opposite sides of the belt 7. In this arrangement, the 
tire 1a or 1b to be tested is arranged to meet the belt in a position 
equivalent to a position of driving on a road. A significant drawback of 
this apparatus, however, is that the design of the testing means is 
exceedingly complex and the belt 7 being used in the apparatus is of a 
special structure and is very expensive. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide novel and 
improved testing means in which the drawbacks related to the apparatus of 
the state of the art described above are avoided, and with which essential 
improvement is, at the same time, provided relative to the state of the 
art. 
These and other objects are attained by the present invention which is 
directed to a device for testing a vehicle tire including anti-skid means 
of the tire, wherein the tire to be tested is pressed against an outer 
surface of another tire while rotating the tires in opposite directions, 
said another tire is a pneumatic tire, and comprising means for disposing 
the tire to be tested and said another tire to be pressed against one 
another such that a contact surface between the tires is substantially 
straight. 
Accordingly, for implementing the above objects and those which will become 
apparent below, the present invention is characterized by the other tire 
acting as the counterpart or pair for the tire to be tested, being a 
pneumatic tire, and the tire to be tested and the other tire being 
disposed to be pressed against one another so that a contact surface 
between the two tires is substantially straight. 
Several advantages are attained with the present invention, of which e.g., 
the following may be set forth. 
In an arrangement conforming to the basic concepts of the present 
invention, two pneumatic tires are urged against one another, whereby a 
straight contact surface is produced between the two tires, at which the 
testing situation is equivalent to normal driving on a road. Since the 
contact surface is straight, the anti-skid means present in the tire to be 
tested are made to meet the surface of the opposite tire in correct 
position. 
Other advantages of the apparatus of the present invention include, for 
instance, testing being feasible at high speeds with the inventive 
apparatus. By turning either tire or both tires, it is easy to generate 
various drift angles with the apparatus of the invention and to study the 
effect of such angles on the tire being tested and on the anti-skid means 
present therein. By coating the rotating tire acting as the counterpart or 
pair for the tire being tested with an appropriate wear layer, e.g. by 
pitching, the wearing effect of the anti-skid means present in the tire 
being tested can be studied rapidly. The measurement made may be simply 
carried out by weighing. 
The other advantages and characteristic features of the invention will 
become apparent from the following detailed description of the invention 
herein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In FIGS. 1 and 2, the tire to be tested is generally denoted by reference 
numeral 10. Reference numeral 10a refers to a rim of the tire to be 
tested, and reference numeral 11 indicates the outer surface of the tire 
10 to be tested. The tire 20 acting as the counterpart or pair for the 
tire 10 to be tested is a pneumatic tire which is conventionally mounted 
on a rim 20a. On an outer surface 21 of the pneumatic tire 20, an 
appropriate wear surface is disposed which is generally denoted by 
reference numeral 22. The wear surface 22 may be provided, e.g., by means 
of pitching the outer surface 21 of the pneumatic tire, or the wear 
surface 22 may, e.g., comprise a steel belt mounted on the surface 21 of 
the tire 20 or an equivalent belt provided with good wear resistance 
properties. 
In the testing means of the invention, the tire 10 being tested and the 
pneumatic tire 20 acting as its counterpart or pair are pressed against 
one another at the same time as they are being rotated. Since both of the 
tires 10 and 20 are pneumatic tires in the testing means of the present 
invention, a straight contact surface is provided at the point of contact 
30 of these tires 10 and 20, whereby the testing situation corresponds to 
conditions on a road. Shape and length of the contact surface 30 between 
the tires 10 and 20 may be varied, e.g. by changing pressures in the tires 
10 and 20. On the other hand, the other tire 20 acting as the counterpart 
or pair for the tire 10 being tested may be larger in diameter than the 
tire 10 being tested, whereby the contact surface 30 between the tires 10 
and 20 is furthermore increased. 
FIG. 2 illustrates the inventive apparatus in a schematic perspective view, 
being simplified for the sake of clarity. In FIG. 2, the body structure 
for the testing means has been omitted. In the embodiment illustrated in 
FIG. 2, the rim 10a of the tire 10 being tested is mounted on a shaft 13 
which is supported by bearings 14 to the body of the testing means. The 
tire 10 being tested is rotated with appropriate drive means 15, for 
instance with an electromotor, from which the power is transmitted to the 
shaft 13 of the tire 10 being tested by means of an appropriate power 
transmission member 16, for instance a belt, chain, or equivalent. 
The power transmission may also be arranged from the drive means 15 to the 
tire 10 being tested in a manner different from FIG. 2, whereby one 
alternative is hydrostatic power transmission between the drive means 15 
and the tire 10 being tested. The other tire 20 acting as the pair or 
counterpart for the tire 10 being tested has, in an equivalent manner, 
been mounted on a rim 20a, this being mounted on another shaft 23. The 
other shaft 23 has respectively been supported on the body of the testing 
means with bearings 24, and according to an embodiment of the present 
invention, brake means have been arranged on the other shaft 23 as 
indicated by reference numeral 25. The brake means 25 may be, e.g., 
mechanical, hydraulic, or controlled so that controlled sliding is 
obtained between the tires 10 and 20. 
In FIG. 2, the tire illustrated as driving the testing means is the tire 10 
to be tested, but naturally either tire 10 or 20 may act as the driving 
tire. If the testing means comprise brake means 25 illustrated in FIG. 2, 
it is clear that such brake means 25 exert its influence on the other 
tire, rather than the tire to which the driving has been transmitted. 
Since the tire 10 being tested in the testing means is pressed against the 
tire 20, it is advantageous if at least one of the tires of the testing 
means is displaceable in a radial direction towards the opposite tire and 
away therefrom. 
In an advantageous embodiment of the present invention, either one or both 
of the tires 10 or 20 of the testing means have been arranged to be 
turnable relative to the opposite tire, whereby a situation may be studied 
with the testing means which is equivalent to driving on curves under road 
conditions. In other words, for changing the drift angle between the 
tires, at least one of the tires may be arranged to be turnable, e.g. in 
an axial direction thereof. 
If a separate steel belt or equivalent is used for the wear surface 22 
acting on the surface of one of the tires 10, the wear surface 22 is 
required to be fixed exceedingly firmly to the other tire 20 in the 
embodiment of the present invention, so that the wear surface 22 cannot 
slide off from the tire 20. In the testing means of the invention, the 
driving speed can also be changed easily during test driving, while 
changing of the drift angle is also additionally simple. The acceleration 
and braking forces present in the apparatus are easy to control, 
especially when one of the tires is provided with brake means 25. 
The testing means of the invention is especially well-suited for studying 
tires provided with anti-skid means. i.e. spiked tires. By providing one 
of the tires 20 with an appropriate wear surface 22, it is possible to 
study the wearing down of the spike against a response surface with the 
testing means. Additionally, the testing means offer exceedingly good 
opportunities to study behavior of a spike when it impinges on a response 
surface, because the testing means of the invention may be conveniently 
provided with an X-ray apparatus with which the contact situation of the 
tires 10 and 20 can be photographed. 
The X-raying may be performed either in a static situation or in a dynamic 
situation during driving, whereby the angle of impingement of the spike on 
the base can be determined. Hence, on the basis of the X-ray photographs 
which have been taken, it is feasible to select, e.g., the spike mounting 
position to be proper in the tire 10 being tested and, on the other hand, 
it is possible to study in the testing means the behavior of various 
spikes in a tire and respectively the effect of tires provided with 
different wear surface patterns respectively on the behavior of the spike 
in a road impingement situation. The required information concerning the 
behavior of the spike is rapidly obtained and well-demonstrated with the 
aid of the X-ray apparatus. 
The invention has been described above with reference to certain exemplary 
features thereof, and to which, however, the present invention is not 
intended to be exclusively confined. Numerous modifications are feasible 
within the scope of the inventive concepts set forth above. In other 
words, the preceding description of the present invention is merely 
exemplary, and is not intended to limit the scope thereof in any way.