Pneumatic-shaped solid tire

A pneumatic-shaped solid tire in which rim slip is improved, the tire main body (4) comprises a tread rubber layer (3) and a base rubber layer (2) made of a rubber composition having a JIS(A) hardness from 75 to 90 in which short cordlike or fiberlike reinforcing materials are not mixed, the thickness (TC) of the base rubber layer measured from the base line (BL) to the radially outer face thereof is 0.3 to 0.7 times the tire section height (TH), and the base rubber layer is provided therein with a radially inner band (7) and a radially outer band (6) which are spaced apart from each other in the radial direction of the tire, each of the bands comprising at least one ply of heat-shrinkable organic fiber cords laid at an angle from 0 to 15 degrees with respect to the tire circumferential direction.

The present invention relates to a solid tire, more particularly a 
pneumatic-shaped solid tire in which rim slip is improved. 
BACKGROUND OF THE INVENTION 
For industrial vehicles, e.g. forklift car, solid tires are widely used. A 
pneumatic-shaped solid tire is one of such solid tires. The 
pneumatic-shaped solid tire has a similar profile to a usual pneumatic 
tire and is mounted on a rim which is originally for the same size 
pneumatic tire. 
For example, in each of Japanese patent publications JP-A-61-44005 and 
JP-A-64-83405, such a pneumatic-shaped solid tire is disclosed, wherein a 
tire main body is composed of three rubber layers, a radially innermost 
base rubber layer, a radially outermost tread rubber layer and an 
in-between cushion rubber layer. The base rubber layer is made of a rubber 
compound reinforced by short organic fiber cords mixed therewith in order 
to greatly increase the compressive elastic modulus or rigidity, which 
intends to improve the engaging force between the tire and rim. Further, 
the rigid base rubber layer extends over the radially outer edge of the 
rim flange, and a reinforcing cord layer is disposed at such a higher 
position being radially outward of the above-mentioned outer edge of the 
rim flange. Therefore, a great engaging force is obtained in the initial 
stage of the tire life. 
However, when the base rubber layer is aged, the friction between the base 
rubber layer and the rim is reduced, and the rubber volume is slightly 
decreased. Accordingly, the engaging force is decreased. As a result, a 
slippage occurs between the tire and rim. 
Even if it is assumed that the reinforcing cord layer produces a hooping 
force, the force can not reach to the rim because a rigid compressive 
resistant rubber layer exists therebetween. Accordingly, such a 
reinforcing cord layer can not prevent the rim slip. 
Further, as the reinforcing cord layer is disposed near or at the boundary 
between the rigid base rubber layer and the relatively soft in-between 
cushion rubber layer, a separation failure of the cushion rubber was 
sometimes observed. 
SUMMARY OF THE INVENTION 
It is therefore, an object of the present invention to provide a 
pneumatic-shaped solid tire, in which rim slip is effectively prevented 
without using, for the base rubber layer, a rigid rubber composition 
reinforced by short organic fiber cords or similar materials. 
According to one aspect of the present invention, a pneumatic-shaped solid 
tire has a main body comprising an annular base rubber layer inserted on a 
rim and an annular tread rubber layer disposed radially outside the base 
rubber layer, wherein 
the base rubber layer is made of a rubber composition in which short 
cordlike or fiberlike reinforcing materials are not mixed, 
the thickness (TC) of the base rubber layer measured from the base line 
(BL) to the radially outer face thereof is 0.3 to 0.7 times the tire 
section height (TH), and 
the base rubber layer is provided therein with a radially inner band (7) 
and a radially outer band (6) which are spaced from apart each other in 
the radial direction of the tire, 
each of the bands comprising at least one ply of organic fiber cords laid 
at an angle from 0 to 15 degrees with respect to the tire circumferential 
direction. 
Preferably, the inner band and the outer band are positioned such that the 
radial heights (h6 and h7) thereof at the thickness center from the base 
line (BL) is in the range from 0.1 to 0.4 times the tire section height 
(TH).

DETAILED DESCRIPTION OF THE EMBODIMENTS 
In FIG. 1, a pneumatic-shaped solid tire 1 has a main body 4 comprising an 
annular base rubber layer 2 and an annular tread rubber layer 3 disposed 
radially outside the base rubber layer 2, and the tire 1 is mounted on a 
rim R, which is originally for pneumatic tires having the same size as the 
tire 1, by inserting the base rubber layer 2 on the rim base RS between 
the rim flanges RF. The rim base RS includes a pair of seat portions that 
slope radially inward from each rim flange. 
The base rubber layer 2 is made of a rubber composition having a JIS(A) 
hardness of 75 to 90, in which reinforcing materials such as short fibers, 
short cords and the like are not mixed. 
The radial height TC of the base rubber layer 2 is in the range from 30 to 
70% of the tire section height TH, and larger than the radial height H of 
the flange RF of the rim R, where each height is measured from the base 
line BL corresponding to the bead base line of the ordinary pneumatic 
tires. 
In this embodiment, the tread rubber layer 3 is composed of 
a cushion rubber part 10 which is a radially inner annular part disposed on 
and around the radially outside of the base rubber layer 2, and 
a tread rubber part 9 which is a radially outer annular part disposed on 
and around the radially outside of the cushion rubber part 10. 
As the radially outer surface of the tread rubber part 9 forms a tread 
face, a rubber composition having a JIS(A) hardness of 60 to 75 and being 
excellent in cut resistance and wear resistance is used for the tread 
rubber part 9. If the hardness is less than 60, the cut resistance and 
wear resistance are not good. If the hardness is more than 75, the grip 
performance of the tire is deteriorated. 
For the cushion rubber part 10, a soft rubber compound having a JIS(A) 
hardness of 40 to 65 is used. For example, natural rubber and butadiene 
rubber containing 30 to 50 PHR of carbon black are preferably used. The 
thickness TB of the cushion rubber part 10 is preferably in the range from 
25 to 50% of the tire section height TH. By providing such cushion part 
10, ride comfort is improved. However, the cushion rubber part 10 may be 
eliminated from the tread rubber layer 3. 
The above-mentioned base rubber layer 2 is provided therein with radially 
spaced bands, a radially outer band 6 and a radially inner band 7. The 
outer band 6 is composed of at least one ply, in this example two plies 6A 
and 6B, of parallel organic fiber cords. The inner band 7 is composed of 
at least one ply, in this example two plies 7A and 7B, of parallel organic 
fiber cords. The organic fiber cords in each ply 6A, 6B, 7A, 7B are laid 
at an angle of 0 to 15 degrees with respect to the tire circumferential 
direction. If the cord angle is more than 15 degrees, the hooping force is 
unfavorably decreased. 
Preferably, the cord angles of the inner band 7 are 0 to 5 degrees, and in 
the outer band 6 the cord angles are larger than those of the inner band 7 
and the adjacent plies are crossed to each other. 
For the band cords, organic fiber cords, preferably heat-shrinkable cords, 
e.g. nylon, polyester and the like are used, and the band cords are 
embedded in a topping rubber whose 30% modulus is 40 to 150 kg/sq.cm. 
The outer and inner bands 6 and 7 are positioned such that the radial 
heights h6 and h7 of the thickness center lines thereof measured from the 
bead base line BL are in the range of 0.1 to 0.4 times the tire section 
height TH. 
EQU 0.4.gtoreq.h6/TH&gt;h7/TH.gtoreq.0.1 
Further, the radial height h6 of the outer band 6 is preferably more than 
0.2 times the tire section height TH. 
EQU 0.4.gtoreq.h6/TH&gt;0.2 
The space (h6-h7) between the inner and outer bands 6 and 7 is preferably 
in the range of 0.2 to 0.3 times the tire section height TH. 
EQU 0.3.gtoreq.(h6-h7).gtoreq.0.2 
The radial distance TD measured from the radially outer face S of the base 
rubber layer 2 to the outermost band 6 is not less than 3%, preferably 5 
to 10% , of the above-mentioned height TC of the base rubber layer 2, 
whereby separation between the base rubber layer and the tread rubber 
layer is prevented. 
The width W6, W7 of each the band 6, 7 is more than 70% and less than 100% 
of the width of the main body 4 measured at the position of the band, 
preferably in the range of 75 to 85%. By retaining a width (w) (about 10% 
width) on each side of the band, the strength of the main body 4 is 
maintained. 
Incidentally, in the case that the band is composed of a plurality of 
plies, the band can be formed by winding a plurality of strips one by one 
or by winding a long strip continuously a plurality of times. Further, the 
band can be formed by spirally winding a long narrow strip or ribbon in 
which one to several organic fiber cords are embedded therein. 
FIGS. 2-4 show the results of tests which were made to measure the tire/rim 
engaging force and the amount of rim slip. In the tests, a tire main body 
composed of a base rubber layer and a tread rubber layer composed of a 
tread rubber part only was used. The thickness (TC) of the base rubber 
layer was 50% of the tire section height (TH), and accordingly the 
thickness of the tread rubber layer was also 50% of the tire section 
height (TH). In the tire main body, one (1) band composed of at least one 
ply of 1500 d polyester cords whose cord count was 38 cords/5 cm was 
disposed. Changing the radial height (h) of the band and the number of the 
band ply, the tire/rim engaging force and the amount of slip were 
measured. 
From the test results, the preferable ranges in the solo band were as 
follows: the radial height of the band measured from the bead base line to 
the band thickness center line is in the range of 20 to 60% of the tire 
section height, and the number of the band ply is in the range of 2 to 4. 
Further, the smaller the band cord angle to the tire circumferential 
direction, the larger the hooping Force. In the case of the solo band, 0 
to 5 degrees is preferable. 
FIG. 6 shows the results of similar tests made with respect to test tires 
in which two radially spaced bands were disposed in the main body. In FIG. 
6, the engaging force is indicated by a circle and the amount of rim slip 
is indicated by "X". 
Table 1 shows the results of similar tests made with respect to Example 
tires 1-3 according to the invention and Reference tires 1-7. The 
specifications thereof are also given in table 1. The tire size was 
7.00-12, and the rim size was 5.00 S. For the band cords, polyester fiber 
cords were used. For the base rubber layer of Reference tire 4, a rubber 
reinforced by short fiber cords was used. 
The engaging force was measured as the maximum force to insert the tire on 
the rim by using an Amslet tester, a tire compression tester. The engaging 
force is indicated by an index based on the assumption that Example tire 
is 100. The larger the index, the larger the engaging force. 
Using a forklift car provided with the test tire, the circumferential 
slippage of the tire caused relatively to the rim during running for 3 
kilometer by a FIG. 8 turn was measured as the amount of rim slip. 
With respect to Example tire 3 and Reference tire 4, a durability test was 
conducted. While a 2.5 ton forklift car was going and returning back on a 
50 m test course, the time to starting of the slippage was measured as the 
durability. The durability is indicated by an index based on the 
assumption that Reference tire 4 is 100. The larger the index, the better 
the durability. 
The invention being thus described, it will be obvious that the same may be 
varied in many ways. Such variations are not to be regarded as a departure 
from the spirit and scope of the invention, and all such modifications as 
would be obvious to one skilled in the art are intended to be included 
within the scope of the following claims. 
TABLE 1 
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Ex. 1 
Ex. 2 
Ex. 3 
Ref. 1 
Ref. 2 
Ref. 3 
Ref. 4 
Ref. 5 
Ref. 6 
Ref. 7 
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TA/TH 0.30 
0.30 
0.70 
0.28 
0.73 
0.38 
0.38 
0.45 
045 0.45 
TB/TH 0.40 
-- -- -- -- -- -- -- -- -- 
TC/TH 0.30 
0.70 
0.30 
0.72 
0.27 
0.62 
0.62 
0.55 
0.55 
0.55 
h6/TH 0.40 
0.40 
0.30 
0.40 
0.20 
0.50 
non 0.50 
0.30 
0.40 
h7/TH 0.10 
0.20 
0.10 
0.30 
0.10 
0.10 
-- 0.5 0.10 
0.20 
JIS(A) hardness of 
75 90 80 90 80 75 80 80 80 80 
base rubber layer 
Band cord angle (deg) 
0 5 3 2 10 8 -- 5 7 5 
Band ply number 
2 2 2 2 2 2 0 2 2 3 
Engaging force (index) 
100 100 100 82 87 70 90 95 90 95 
Rim slip (index) 
100 100 100 180 270 400 200 150 200 200 
Durability (index) 
-- -- 320 -- -- -- 100 -- -- -- 
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