CA1045532A - Radial tire for motor vehicles - Google Patents
Radial tire for motor vehiclesInfo
- Publication number
- CA1045532A CA1045532A CA269,063A CA269063A CA1045532A CA 1045532 A CA1045532 A CA 1045532A CA 269063 A CA269063 A CA 269063A CA 1045532 A CA1045532 A CA 1045532A
- Authority
- CA
- Canada
- Prior art keywords
- cords
- layer
- layers
- tire
- metallic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C9/00—Reinforcements or ply arrangement of pneumatic tyres
- B60C9/18—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers
- B60C9/20—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel
- B60C9/2003—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel characterised by the materials of the belt cords
- B60C9/2006—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel characterised by the materials of the belt cords consisting of steel cord plies only
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C9/00—Reinforcements or ply arrangement of pneumatic tyres
- B60C9/18—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers
- B60C9/20—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel
- B60C9/2003—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel characterised by the materials of the belt cords
- B60C9/2009—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel characterised by the materials of the belt cords comprising plies of different materials
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Tires In General (AREA)
- Ropes Or Cables (AREA)
Abstract
IMPROVED RADIAL TIRE FOR MOTOR VEHICLES
Abstract of the Disclosure A pneumatic tire having a radial carcass is provided with a reinforcing structure between the carcass and tread having first and second layers of metallic cords having an ultimate elongation of about 3%. The cords of the first and second layers are dis-posed parallel to each other and at angles of about 5° to about 30° with the axis of the tire body with the cords in one layer crossing the cords of the other layer. A third layer of metallic cords having an ultimate elongation of from about 4% to about 8%
is disposed radially outwardly over the first two layers. The cords in the third layer are wound about the carcass in a plane which is substantially parallel to the longitudinal direction of the tire. The resulting assembly of layers provides a reinforcing structure which is adapted to withstand the tension stresses exerted on tires used on heavy vehicles such as buses and trucks even at high speed, giving also high steering characteristics to the tire.
Abstract of the Disclosure A pneumatic tire having a radial carcass is provided with a reinforcing structure between the carcass and tread having first and second layers of metallic cords having an ultimate elongation of about 3%. The cords of the first and second layers are dis-posed parallel to each other and at angles of about 5° to about 30° with the axis of the tire body with the cords in one layer crossing the cords of the other layer. A third layer of metallic cords having an ultimate elongation of from about 4% to about 8%
is disposed radially outwardly over the first two layers. The cords in the third layer are wound about the carcass in a plane which is substantially parallel to the longitudinal direction of the tire. The resulting assembly of layers provides a reinforcing structure which is adapted to withstand the tension stresses exerted on tires used on heavy vehicles such as buses and trucks even at high speed, giving also high steering characteristics to the tire.
Description
1~4553~ ~
The present invention relates to pneuma-tic tires ~or vehicle wheels and in particular to tires provided with a radial carcass (i.e., a carcass whose cords lie on meridian planes or , form small angles with the planes) particularly suitable for heavy' vehicles for normal and heavy duty and intended to be u,sed for long dis-tances at normal and high speed.
It is known that radial tires are usually provided with a structure which includes one or more reinforcing layers arranged at the crown zone of the carcass below the tread. The reinforcing .
layer is provided to wi-thstand the tension stresses to which the . tire is subjected, either because of the inflation pressure or in heavy service conditions due to the high speed.
Clearl.y, in case of laxge tires intended to be used on motor vehicles for normal ~nd heavy duty, such as buses or coaches , or motor vehicles for industrial use, the tension stresses which are e,xerted on the reinforcing structure are very high. Hence, it is necessary to provide such tires with a reinforcing struc-turl~
which is extremely resistant to tension stxesses wi-thout using too many layers o reinforcing material because this would produc~
an increase of the weight and/or size of the -tire and would re-quire an incxease of the inflation pressure with the consequent increase o the tension stresses on the reinforcing structure.
For these reasons, the trend cor.~ercially is to form the reinforcing structure with the lowest number of layers possible ., of reinorcing material havin~ a high modulus oE elas-ticity. .
Theoretically, the reinforcing structure which would assure the : maximum resistance to tension stresses should be that constituted by one or more layers of metallic cords, having an ul-timclte . ' , -2~ .
,~ ,.. ~.. ~ .. ,.. , . . - - .
( ` ~: ~
~04S53;2 ,, elongation of about 3% and oriented according to a direction which is substantially parallel to ~he longitudinal direction of the tire. However, such a rein~orcing structure is not satisfactory -because the tire has an undesirable driving behavior, particularly as regards transverse stability when the tire runs both along a curved trajectory and along a straight onle.
Consequently, the reinforcing structure usually used to achieve the above described aims has two layers of metallic cords arranged so that the cords are parallel to one an~ther in each layer-and are symmetrically inclined with respect to the longitu-dinal airection of the tire at a relatively small angle of betweer about 5 and about 30.
In such a way, the intrinsic rigidity of the material of the two Iayers is attenuated by a certain flexibility of the re-sulting reinforcing structure. In fact, the tension strezses due to the tire inflation result in a reduction of the angle of incli - -nation of the cords of the two layers and a consequent increase of the tire diameter. Consequently, the reinforcing structure is qulte satisfactory also as regards the torsional or transverse stiffness. This provides a tire which offers a good driving behav~or, particularly as regards both the driving stability when the tire runs along a straight trajectory and the lack of drift when the tire runs along a curved trajectory. , However, especially in the large size tires which utilize a radial carcass having a mono-ply of metallic cords, it is found that, although the aforesaid reinforcing s-tructure e~fectively withstands the tension stresses to which the tire is subjected, the reinforcing structure is not sufficient to co~mterbalance ~he -. . ~
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high carcass flexibility. Consequently, the tire does not respond satisfactorily -to s-teering. Therefore, it is necessary to add other layers to the reinforcing structure which act as a stabilizer. In general, a further strip of metallic cords is used which is arrang-ed so -that ~he cords are inclined with respect to -the longitudinal direction at a high angle, for example, an angle of 60.
It is an object of this invention -to provide a pneumatic tire having a radial carcass which combines high resistance to tension stresses and good driving -stability. Another object of the invention is to pro-vide a pneumatic tire having a radial carcass and a tread with a reinforcing structure between the carcass and tread which has su~ic:ien-t resistance to tension stresses to adap-t the tire for use on heavy vehicles such as buses, trucks and the like and which does not significantly adversely effect the s-teering charac-ter-istics of the tire.
Other cobjects will become apparent from the follow-ing description of the inven-tion wi-th reference to -the accompanying drawing wherein.
Figure 1 illustrates in a partial cross-sec-tion one embodiment of the tire provided by the invention;
Figure 2 illustrates in a fragmentary perspective view the tir-e shown in Figure 1 with parts removed in order to better illustrate the arrangement of the various cords; and Figure 3 illustrates in cross-section a second em-bodiment of the tire of the presen-t invention.
It has now been found, surprisingly, that the appli-cation to a reinforcing structure having two layers of metallic cords of ll ~
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the type described of a third layer of metallic cords having a relatively high elongation and arranged in a direction which is substantially parallel to the longitudinal direction of the tire, not only provides the tires with the driv:ing stability effects :
which until now were considered due exclusively to the strips of metallic cords having a high inclination with respect to the longitudinal direction, but also a very high resistance to the tension stresses. More specifically, such a reinforcing structur~
has a high enough resistance so that it withstands not only the .
tension stresses due to the inflation pressure of the tire, but .
also those which occur when the tire r~ms at high speed. .
Accordingly, the present invention provides a pneumatic .
~ixe for motor ~ehicles adapted to be used for normal or.heavy duty vehicles having a reinorcing structure comprising at least two layers which have widths which are about equal to the width .
of the tread and are formed by me:tallic cords having an ultimate elongation of about 3%, the cords being parallel to one.another : in each layer and crossed with respect to those o the other . layer, the two layers arrangecl so that the cords are inclined with ' respect to the longitudinal direction of the tire at an angle of ¦
5 to 30. The tire has radially outwardly from the first two layers at least one layer of metallic cords ha~ing a width which .
is substantially equal to that of the tread, the outer layer bein composed of metallic cords which are parallel to one another and are arranged in a longitudinal direction, the metallic cords having an ultimate elongation of about 4% ~o about 8~. :
The tires having the assembly of reinforcing layers as ~
described above can be of the type intended to be mounted on the : :
1()9~5532 ' ~
motor vehicle with or without the inner tube; moreover, al-though the assembly of rein~orcing layers is extremely advantageous for tires having large sizes provided with a carcass constituted by a radial metallic mono-ply, it is understood that it will produce just as good results if applied to tires provided with a radial carcass having a plurality of plies and constituted by cords of -textile material.
Preferably, the layer of metallic cords belong:ing to the reinforcing structure, which is immediately below the layer of metallic cords arranged in a longitudinal direction, has a width which is at least equal to that of the layer. The other layer of the r~inforcing structure has a slightly smaller width, so that it is disposed inwardly with respect to the overhanging layer.
As set forth above, it has been found that the large size ~15 tires, particularly those intended to be used for normal and heavy duty, which are provided with the assembly of reinforcing layers of this invention are able to offer high perfoxmances not ~ :
A . only in service conditions at normal speed but also at higher speeds, and they have a very good driving behavior.
The effect of the assembly of reinforcing layers appears to be still more surprising, if it is taken into account that tests carried out on similar tires, having the same reinforcing --structure of the first and second layers of metallic cords having -~
an ultimate elvngation of about 3% plus a third superimposed laye of metallic cords like those of the first ana second layer except that the cords are arranged in the longitudinal direction have shown a clear adverse effect on the driving and comfort charac-teristics of the tire. In other words, an assembly of reinforcin . ' ' . . '"~'~
' . , ' . :~
~'~' . .~
.,, '. .
. . .
~ S~32 layers which combines a layer of metallic cords of about 3% elongation arranged in the longitudinal direc-tion with the first and second layers used in this inven-tion improves the resistance to -tension stresses bu-t the combination has the disadvantage of making steering of the vehicle more difficult. It has been found that in the assembly of the three layers of this invention, the layer of longitudinally disposed met-allic cords supports almos-t all of the stresses. There-fore, the first and second layers are no-t under tension and do not interfere with the driving stabili-ty charac-teristics of the -tire.
The improvement provided by the reinforcing assembly of the invention is probably due to the unique combina-tion of relative inextensible metallic cords in -the first two layers disposed at an angle inclined with res-pect to the longitudinal axis of the tire with the more extensible metallic cords of the radial outer layer.
Apparently, the radial outer layer has a bearing ac-tion and cooperates wi-th the other two layers.
The metallic cords having an ultimate elonga-tion be-tween ~% and 8%, which hereinaf-ter we will can "ex-tens-ible", are per se widely known to one skilled in -the arts. They are consti-tuted by s-trands formed by a plurality of wires twisted together, and ei-ther the individual strands or the cord are all wound up heli-cally in the same sense.
Vice versa, the metallic cords having an ultimate elongation of about 3%, which are also known per se, ~re cons-tituted by strands formed by a plurali-ty of wires helically wound up in an opposite sense with respect to that of the cord.
According to a preferred embod:imen-t of the present invention, the layer or the layers of the extensible me-tallic cords ~5532 are formed by a single extensible cord helically wound with the convolutions of the helix arranged in -the long-itudinal direc-tion.
According to ano-ther preferred embodimen-t, the layer or each of the ex-tensible metallic cords layers is formed by strips placed side by side, each of which has a width equal -to a portion of the tread width and extends longitudinally on the whole development of the tire-Referring now to Figure l, one embodimen-t of a tubeless tire of the size llR22.5 has a tread 1 and a carcass 2 constituted by a mono-ply of metallic cords lying in a radial plane or forming small angles with the radial planes.
Between the tread l and the carcass 2 an assembly of reinforcing layers is inserted. This assembly has first and second layers 3 and 4 of me~allic cords having an ultimate elongation of about 3% and a third layer 5 radially outwardly with respect to -the o-ther two layers 3 and 4 of metallic cords having an ulti-mate elongation of 7%. The layers 3 and 4, as shown more clearly in Figure 2, are arranged so that -their metallic cords are parallel -to one ano-ther in each layer and are inclined respectively at an angleC~?nd L~ 18 with respect to the longi-tudinal direction of the tire.
The layer 5 has its own metallic cords arranged in a longitudinal direction.
The aforesaid assembly of layers 3,4 and 5 has a width substantially equal to -that of the tread l.
Since, as is customary, the reinforcing layers are arranged according to a certain gradua-tion, it is pre-ferred according to the present invention -that -the layer 4 has, in the reinforcing struc-ture, the wider wid-th so as to project slightly from bo-th sides with respec-t to -the layer 5, while -the layer 3 has a slightly smaller w1~th with ., .
s~ ~
respect to tha-t of the layer 4. In such a way, the layer 5 has the me-tallic cords completely suppor-ted by the layer 4 along its whole width. This insures a lower elongation of the reinforcing assembly at its lateral ends, with consequen-t high perfc>rmance of the tire in service at high speeds. Layer 5 is disposed on the layer 4 by helically winding an extensible metallic cord over layer 4 or one or more strips of cord fabric of extensible metallic cords are superimposed on layer 4.
Specifically as regards the metallic cords, those of layers 3 and 4 which, as aforesaid, have an ultima-te elongation equal -to about 3%, are each Eormed by seven strands twisted together, each strand being formed by the helical winding of four steel wires having a d:ia-me;terequal to 0.22 mm. The strands are twisted toge-ther according to a winding sense opposite to that of the bwisting of the individual strands. The metallic cords forming the layer 5 and having an ultimate elong-ation of 7% are each composed of three strands, twisted together, each strand being formed by the winding of seven steel wires having a diame-ter equal to 0.20 mm.
The s-trands are twisted -together accord:ing to a wind-ong sense equal to that of the twis-ting of the indiv-idual strands, with the twisting pi-tch of each strand -being equal to about 4 mm and wi-th the twisting pitch of the cord being equal to abo~t 6.5 mm. -Figure 3 illus-trates an alternate embodiment of the presen-t invention according to which the -tire 6 has the ass~mbly of reinforcing layers constitu-ted by two layers of metallic cords 7 and 8, abou-t equal to -the two layers 3 and 4 of Figures 1 and 2 and by -the layer 9 of metallic cords having an ultima-te elongation equal to 7%. Layer 9 consists of -three s-trips, respec-tively ~, 9 _ ~Oa~3Z
ll and 12, placed side by side with respec-t -to one another so as to cover the whole width of the under-lying strip 8.
The central s-trip ll is a-t leas-t twice the wid-th of the two other strips lO and 12. In order to dis-tinguish layers lO, ll and 12 from each other, the cords of strips lO and 12 are indica-ted in Figure 3 with filled circular section while the cords of strip ~:
11 are shown as mere circular sections. Actually the .
cords of all three strips may be the same. : -Because of the curvature of the assembly of the reinforcing layers, these s-trips 10 and 12 have a longitudinal development lower than the corresponding development of the strip 11. Preferably the ends of each strip are joined together a-t poin-ts so -that each . ~:
joint is staggered with respect to the other, for .:.
example by 120. .
In order to demonstrate -the improvement of -the :
tires of the.invention, the embodiment illustra-ted in Figures~ to 3 of the drawing were compared both with conventional tires and with tires having rein- .~ ;
forcing structure comprising, in a way per se known, longitudinally arranged, reinforcing elements differen-t from those of the present invention.
More particularly, the tires subjected to the tests were:
Tires:A
Tubeless tires, size llR22.5 (in accordance with -the present invention) provided with a mono-ply radial met-allic carcass 7 with a reinforcing struc-ture, arranged between the tread and the carcass, consisting of first and second layers of metallic cords having an ultimate elongation of about 3~, crossed with one another and inclined with respect to the longi-tudinal d:irecti.on of the tire at an angle of 18 and wi-th a third layer of me-tallic :~ .
-- l o --cords having an ultimate elongation of 7%, the third layer being arranged radially out~ide the first and second layers and having its cords arranged in the longitudinal direction of th~ tire.
Tires B
' :' Tubeless tires, size llR22.5, provided with a mono-ply radial metallic carcass, with a reinforcing structure consisting of first and second layers of metallic cordc having an ultimate -elongation of about 3%, crossed with one another and inclined with respect to the longitudinal direction of the tire at an angle of 18, and with a stabilizer strip, arranged in a radially inner position with respect to the first and second layers, constituted by me*allic cords having an ultimate elongation of ; about 3% and inclined at an angle of 60 with respect to the -longitudinal direction (conventIonal tires).
Tires C
Tubeless tires, size llR22.5, provided with a mono-ply radial metallic carcass and with a reinforcing structure consist-ing of three layers of metallic cords, all the cords having an ultimate elongation o~ about 3%, two of the layers having the cords inclined at an angle of 18 and crossed with one another, -while the third layer, radially outward to the ~irst ones, had the cords arranged in a longitudinal direction.
Tires ~
Tubeless tires~ size llR22.5, provided with a mono-ply radial metallic carcass, with a reinforcing structure consisting of two layers of metallic cords having an ultimate elongation of about 3% cros~ed with one another and inclined at an angle of 18 with respect t~ the 1ongltudinal directio j and wi~h a lay~r of ~)45~3~
polyamide cords arranged in a longitudinal direction, in a rad:i-ally outer position wi~h respect to ~he first ones.
Tests The above indicated tires were first o~ all subjected to laboratory tests in order to evaluate the detachment re~istance o~
the reinforcing structure, par-ticularly at high speeds. In prac-tice, the test consisted of subjecting the tires to increasing speeds, each tire being mounted on a rim, in~lated to a pressure o~ 8 kg/cm~ and put under a load of 2,550 kg (pressure and load comparable with those maximum advissible in use). The imposed speeds were at first 70 km/h for 5 hours, with an increasing of the speed of 10 km/h every -two hours. The obtained results wexe:
Tire~ A reached 160 km/h before detachment of the re:in-Eorcing structure.
Tires B reached 14~ km/h before detachment of the rein-forcing structure.
Tires C reached 160 km/h before detachment of the rein-forcing struc~ure.
Tixes D reached 140 km/h before detachment of the rein-forcincJ structure.
From the above, :it is noted that tires whose rein~orcing structure comprises metallic cords arranged in the longitudinal direction (both having a low and high elongation) givé the better results.
Then the power consumption resulting from using the differ-ent types of test tires was de-termined. It was found -that tires A, C and D gave a power consu~ption analogous and lower than that resulting ~rom using tires B.
., :' ., ' :~04~3~
Then the steering response (an extremely important characteristic, as the test tires were intended -to be used for duty at high speeds) was checked. It was -found that tires A and B had good steering characteris-tics while tires C and D had very poor steering charac-teristics.
Because of the poor steering characteristics oftires C and D -they were not road tested .
Road tests with tires A and B werecarried out on a running track. Each typelof tire was mounted on a truck each tire having an overload of 20% with respect -to its maximum capaci-ty. The tires were first run 30,000 ; Icm, at a speed of 122 km/h, along a straight stretch.
At the end of this firs-t par-t of the -test it was noted that the tread of -tires A and B showed an equivalen-t wear, and neither type had significant craclcings or damages. In the second part of -the -test, the truck was run over a curved -track and reverse curved -track.
After a run o-f 1100-1900 km, tires B showed detachments among the layers of the reinforcing struc-ture so that ~-the test had to be stopped. Tires A ins-tead ran with-out de-tachmen-t until the whole tread was worn.
The results obtained from all these tests demonstrate that the -tires according to -the present invention have improved performances in every sense over the o-ther test tires although the structure of the reinforcing layers at first sight may appear to be only slightly different from that of the known tires.
Although the invention has been described in detail for the purpose of illustration, it is to be understood -that such detail is solely for -that purpose and that variations can be made therein by those skilled in the art without departing from -the spirit and scope of -the invention except as it may be limi-ted by -the claims.
, .~ .
The present invention relates to pneuma-tic tires ~or vehicle wheels and in particular to tires provided with a radial carcass (i.e., a carcass whose cords lie on meridian planes or , form small angles with the planes) particularly suitable for heavy' vehicles for normal and heavy duty and intended to be u,sed for long dis-tances at normal and high speed.
It is known that radial tires are usually provided with a structure which includes one or more reinforcing layers arranged at the crown zone of the carcass below the tread. The reinforcing .
layer is provided to wi-thstand the tension stresses to which the . tire is subjected, either because of the inflation pressure or in heavy service conditions due to the high speed.
Clearl.y, in case of laxge tires intended to be used on motor vehicles for normal ~nd heavy duty, such as buses or coaches , or motor vehicles for industrial use, the tension stresses which are e,xerted on the reinforcing structure are very high. Hence, it is necessary to provide such tires with a reinforcing struc-turl~
which is extremely resistant to tension stxesses wi-thout using too many layers o reinforcing material because this would produc~
an increase of the weight and/or size of the -tire and would re-quire an incxease of the inflation pressure with the consequent increase o the tension stresses on the reinforcing structure.
For these reasons, the trend cor.~ercially is to form the reinforcing structure with the lowest number of layers possible ., of reinorcing material havin~ a high modulus oE elas-ticity. .
Theoretically, the reinforcing structure which would assure the : maximum resistance to tension stresses should be that constituted by one or more layers of metallic cords, having an ul-timclte . ' , -2~ .
,~ ,.. ~.. ~ .. ,.. , . . - - .
( ` ~: ~
~04S53;2 ,, elongation of about 3% and oriented according to a direction which is substantially parallel to ~he longitudinal direction of the tire. However, such a rein~orcing structure is not satisfactory -because the tire has an undesirable driving behavior, particularly as regards transverse stability when the tire runs both along a curved trajectory and along a straight onle.
Consequently, the reinforcing structure usually used to achieve the above described aims has two layers of metallic cords arranged so that the cords are parallel to one an~ther in each layer-and are symmetrically inclined with respect to the longitu-dinal airection of the tire at a relatively small angle of betweer about 5 and about 30.
In such a way, the intrinsic rigidity of the material of the two Iayers is attenuated by a certain flexibility of the re-sulting reinforcing structure. In fact, the tension strezses due to the tire inflation result in a reduction of the angle of incli - -nation of the cords of the two layers and a consequent increase of the tire diameter. Consequently, the reinforcing structure is qulte satisfactory also as regards the torsional or transverse stiffness. This provides a tire which offers a good driving behav~or, particularly as regards both the driving stability when the tire runs along a straight trajectory and the lack of drift when the tire runs along a curved trajectory. , However, especially in the large size tires which utilize a radial carcass having a mono-ply of metallic cords, it is found that, although the aforesaid reinforcing s-tructure e~fectively withstands the tension stresses to which the tire is subjected, the reinforcing structure is not sufficient to co~mterbalance ~he -. . ~
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. . .~, . . '''~'.'.:
. ', ' . ' . , '.
_ . ~
. . ... ... . . . : . : .: .. ' :: .
~0~S~3Z
high carcass flexibility. Consequently, the tire does not respond satisfactorily -to s-teering. Therefore, it is necessary to add other layers to the reinforcing structure which act as a stabilizer. In general, a further strip of metallic cords is used which is arrang-ed so -that ~he cords are inclined with respect to -the longitudinal direction at a high angle, for example, an angle of 60.
It is an object of this invention -to provide a pneumatic tire having a radial carcass which combines high resistance to tension stresses and good driving -stability. Another object of the invention is to pro-vide a pneumatic tire having a radial carcass and a tread with a reinforcing structure between the carcass and tread which has su~ic:ien-t resistance to tension stresses to adap-t the tire for use on heavy vehicles such as buses, trucks and the like and which does not significantly adversely effect the s-teering charac-ter-istics of the tire.
Other cobjects will become apparent from the follow-ing description of the inven-tion wi-th reference to -the accompanying drawing wherein.
Figure 1 illustrates in a partial cross-sec-tion one embodiment of the tire provided by the invention;
Figure 2 illustrates in a fragmentary perspective view the tir-e shown in Figure 1 with parts removed in order to better illustrate the arrangement of the various cords; and Figure 3 illustrates in cross-section a second em-bodiment of the tire of the presen-t invention.
It has now been found, surprisingly, that the appli-cation to a reinforcing structure having two layers of metallic cords of ll ~
~ 53Z ~
the type described of a third layer of metallic cords having a relatively high elongation and arranged in a direction which is substantially parallel to the longitudinal direction of the tire, not only provides the tires with the driv:ing stability effects :
which until now were considered due exclusively to the strips of metallic cords having a high inclination with respect to the longitudinal direction, but also a very high resistance to the tension stresses. More specifically, such a reinforcing structur~
has a high enough resistance so that it withstands not only the .
tension stresses due to the inflation pressure of the tire, but .
also those which occur when the tire r~ms at high speed. .
Accordingly, the present invention provides a pneumatic .
~ixe for motor ~ehicles adapted to be used for normal or.heavy duty vehicles having a reinorcing structure comprising at least two layers which have widths which are about equal to the width .
of the tread and are formed by me:tallic cords having an ultimate elongation of about 3%, the cords being parallel to one.another : in each layer and crossed with respect to those o the other . layer, the two layers arrangecl so that the cords are inclined with ' respect to the longitudinal direction of the tire at an angle of ¦
5 to 30. The tire has radially outwardly from the first two layers at least one layer of metallic cords ha~ing a width which .
is substantially equal to that of the tread, the outer layer bein composed of metallic cords which are parallel to one another and are arranged in a longitudinal direction, the metallic cords having an ultimate elongation of about 4% ~o about 8~. :
The tires having the assembly of reinforcing layers as ~
described above can be of the type intended to be mounted on the : :
1()9~5532 ' ~
motor vehicle with or without the inner tube; moreover, al-though the assembly of rein~orcing layers is extremely advantageous for tires having large sizes provided with a carcass constituted by a radial metallic mono-ply, it is understood that it will produce just as good results if applied to tires provided with a radial carcass having a plurality of plies and constituted by cords of -textile material.
Preferably, the layer of metallic cords belong:ing to the reinforcing structure, which is immediately below the layer of metallic cords arranged in a longitudinal direction, has a width which is at least equal to that of the layer. The other layer of the r~inforcing structure has a slightly smaller width, so that it is disposed inwardly with respect to the overhanging layer.
As set forth above, it has been found that the large size ~15 tires, particularly those intended to be used for normal and heavy duty, which are provided with the assembly of reinforcing layers of this invention are able to offer high perfoxmances not ~ :
A . only in service conditions at normal speed but also at higher speeds, and they have a very good driving behavior.
The effect of the assembly of reinforcing layers appears to be still more surprising, if it is taken into account that tests carried out on similar tires, having the same reinforcing --structure of the first and second layers of metallic cords having -~
an ultimate elvngation of about 3% plus a third superimposed laye of metallic cords like those of the first ana second layer except that the cords are arranged in the longitudinal direction have shown a clear adverse effect on the driving and comfort charac-teristics of the tire. In other words, an assembly of reinforcin . ' ' . . '"~'~
' . , ' . :~
~'~' . .~
.,, '. .
. . .
~ S~32 layers which combines a layer of metallic cords of about 3% elongation arranged in the longitudinal direc-tion with the first and second layers used in this inven-tion improves the resistance to -tension stresses bu-t the combination has the disadvantage of making steering of the vehicle more difficult. It has been found that in the assembly of the three layers of this invention, the layer of longitudinally disposed met-allic cords supports almos-t all of the stresses. There-fore, the first and second layers are no-t under tension and do not interfere with the driving stabili-ty charac-teristics of the -tire.
The improvement provided by the reinforcing assembly of the invention is probably due to the unique combina-tion of relative inextensible metallic cords in -the first two layers disposed at an angle inclined with res-pect to the longitudinal axis of the tire with the more extensible metallic cords of the radial outer layer.
Apparently, the radial outer layer has a bearing ac-tion and cooperates wi-th the other two layers.
The metallic cords having an ultimate elonga-tion be-tween ~% and 8%, which hereinaf-ter we will can "ex-tens-ible", are per se widely known to one skilled in -the arts. They are consti-tuted by s-trands formed by a plurality of wires twisted together, and ei-ther the individual strands or the cord are all wound up heli-cally in the same sense.
Vice versa, the metallic cords having an ultimate elongation of about 3%, which are also known per se, ~re cons-tituted by strands formed by a plurali-ty of wires helically wound up in an opposite sense with respect to that of the cord.
According to a preferred embod:imen-t of the present invention, the layer or the layers of the extensible me-tallic cords ~5532 are formed by a single extensible cord helically wound with the convolutions of the helix arranged in -the long-itudinal direc-tion.
According to ano-ther preferred embodimen-t, the layer or each of the ex-tensible metallic cords layers is formed by strips placed side by side, each of which has a width equal -to a portion of the tread width and extends longitudinally on the whole development of the tire-Referring now to Figure l, one embodimen-t of a tubeless tire of the size llR22.5 has a tread 1 and a carcass 2 constituted by a mono-ply of metallic cords lying in a radial plane or forming small angles with the radial planes.
Between the tread l and the carcass 2 an assembly of reinforcing layers is inserted. This assembly has first and second layers 3 and 4 of me~allic cords having an ultimate elongation of about 3% and a third layer 5 radially outwardly with respect to -the o-ther two layers 3 and 4 of metallic cords having an ulti-mate elongation of 7%. The layers 3 and 4, as shown more clearly in Figure 2, are arranged so that -their metallic cords are parallel -to one ano-ther in each layer and are inclined respectively at an angleC~?nd L~ 18 with respect to the longi-tudinal direction of the tire.
The layer 5 has its own metallic cords arranged in a longitudinal direction.
The aforesaid assembly of layers 3,4 and 5 has a width substantially equal to -that of the tread l.
Since, as is customary, the reinforcing layers are arranged according to a certain gradua-tion, it is pre-ferred according to the present invention -that -the layer 4 has, in the reinforcing struc-ture, the wider wid-th so as to project slightly from bo-th sides with respec-t to -the layer 5, while -the layer 3 has a slightly smaller w1~th with ., .
s~ ~
respect to tha-t of the layer 4. In such a way, the layer 5 has the me-tallic cords completely suppor-ted by the layer 4 along its whole width. This insures a lower elongation of the reinforcing assembly at its lateral ends, with consequen-t high perfc>rmance of the tire in service at high speeds. Layer 5 is disposed on the layer 4 by helically winding an extensible metallic cord over layer 4 or one or more strips of cord fabric of extensible metallic cords are superimposed on layer 4.
Specifically as regards the metallic cords, those of layers 3 and 4 which, as aforesaid, have an ultima-te elongation equal -to about 3%, are each Eormed by seven strands twisted together, each strand being formed by the helical winding of four steel wires having a d:ia-me;terequal to 0.22 mm. The strands are twisted toge-ther according to a winding sense opposite to that of the bwisting of the individual strands. The metallic cords forming the layer 5 and having an ultimate elong-ation of 7% are each composed of three strands, twisted together, each strand being formed by the winding of seven steel wires having a diame-ter equal to 0.20 mm.
The s-trands are twisted -together accord:ing to a wind-ong sense equal to that of the twis-ting of the indiv-idual strands, with the twisting pi-tch of each strand -being equal to about 4 mm and wi-th the twisting pitch of the cord being equal to abo~t 6.5 mm. -Figure 3 illus-trates an alternate embodiment of the presen-t invention according to which the -tire 6 has the ass~mbly of reinforcing layers constitu-ted by two layers of metallic cords 7 and 8, abou-t equal to -the two layers 3 and 4 of Figures 1 and 2 and by -the layer 9 of metallic cords having an ultima-te elongation equal to 7%. Layer 9 consists of -three s-trips, respec-tively ~, 9 _ ~Oa~3Z
ll and 12, placed side by side with respec-t -to one another so as to cover the whole width of the under-lying strip 8.
The central s-trip ll is a-t leas-t twice the wid-th of the two other strips lO and 12. In order to dis-tinguish layers lO, ll and 12 from each other, the cords of strips lO and 12 are indica-ted in Figure 3 with filled circular section while the cords of strip ~:
11 are shown as mere circular sections. Actually the .
cords of all three strips may be the same. : -Because of the curvature of the assembly of the reinforcing layers, these s-trips 10 and 12 have a longitudinal development lower than the corresponding development of the strip 11. Preferably the ends of each strip are joined together a-t poin-ts so -that each . ~:
joint is staggered with respect to the other, for .:.
example by 120. .
In order to demonstrate -the improvement of -the :
tires of the.invention, the embodiment illustra-ted in Figures~ to 3 of the drawing were compared both with conventional tires and with tires having rein- .~ ;
forcing structure comprising, in a way per se known, longitudinally arranged, reinforcing elements differen-t from those of the present invention.
More particularly, the tires subjected to the tests were:
Tires:A
Tubeless tires, size llR22.5 (in accordance with -the present invention) provided with a mono-ply radial met-allic carcass 7 with a reinforcing struc-ture, arranged between the tread and the carcass, consisting of first and second layers of metallic cords having an ultimate elongation of about 3~, crossed with one another and inclined with respect to the longi-tudinal d:irecti.on of the tire at an angle of 18 and wi-th a third layer of me-tallic :~ .
-- l o --cords having an ultimate elongation of 7%, the third layer being arranged radially out~ide the first and second layers and having its cords arranged in the longitudinal direction of th~ tire.
Tires B
' :' Tubeless tires, size llR22.5, provided with a mono-ply radial metallic carcass, with a reinforcing structure consisting of first and second layers of metallic cordc having an ultimate -elongation of about 3%, crossed with one another and inclined with respect to the longitudinal direction of the tire at an angle of 18, and with a stabilizer strip, arranged in a radially inner position with respect to the first and second layers, constituted by me*allic cords having an ultimate elongation of ; about 3% and inclined at an angle of 60 with respect to the -longitudinal direction (conventIonal tires).
Tires C
Tubeless tires, size llR22.5, provided with a mono-ply radial metallic carcass and with a reinforcing structure consist-ing of three layers of metallic cords, all the cords having an ultimate elongation o~ about 3%, two of the layers having the cords inclined at an angle of 18 and crossed with one another, -while the third layer, radially outward to the ~irst ones, had the cords arranged in a longitudinal direction.
Tires ~
Tubeless tires~ size llR22.5, provided with a mono-ply radial metallic carcass, with a reinforcing structure consisting of two layers of metallic cords having an ultimate elongation of about 3% cros~ed with one another and inclined at an angle of 18 with respect t~ the 1ongltudinal directio j and wi~h a lay~r of ~)45~3~
polyamide cords arranged in a longitudinal direction, in a rad:i-ally outer position wi~h respect to ~he first ones.
Tests The above indicated tires were first o~ all subjected to laboratory tests in order to evaluate the detachment re~istance o~
the reinforcing structure, par-ticularly at high speeds. In prac-tice, the test consisted of subjecting the tires to increasing speeds, each tire being mounted on a rim, in~lated to a pressure o~ 8 kg/cm~ and put under a load of 2,550 kg (pressure and load comparable with those maximum advissible in use). The imposed speeds were at first 70 km/h for 5 hours, with an increasing of the speed of 10 km/h every -two hours. The obtained results wexe:
Tire~ A reached 160 km/h before detachment of the re:in-Eorcing structure.
Tires B reached 14~ km/h before detachment of the rein-forcing structure.
Tires C reached 160 km/h before detachment of the rein-forcing struc~ure.
Tixes D reached 140 km/h before detachment of the rein-forcincJ structure.
From the above, :it is noted that tires whose rein~orcing structure comprises metallic cords arranged in the longitudinal direction (both having a low and high elongation) givé the better results.
Then the power consumption resulting from using the differ-ent types of test tires was de-termined. It was found -that tires A, C and D gave a power consu~ption analogous and lower than that resulting ~rom using tires B.
., :' ., ' :~04~3~
Then the steering response (an extremely important characteristic, as the test tires were intended -to be used for duty at high speeds) was checked. It was -found that tires A and B had good steering characteris-tics while tires C and D had very poor steering charac-teristics.
Because of the poor steering characteristics oftires C and D -they were not road tested .
Road tests with tires A and B werecarried out on a running track. Each typelof tire was mounted on a truck each tire having an overload of 20% with respect -to its maximum capaci-ty. The tires were first run 30,000 ; Icm, at a speed of 122 km/h, along a straight stretch.
At the end of this firs-t par-t of the -test it was noted that the tread of -tires A and B showed an equivalen-t wear, and neither type had significant craclcings or damages. In the second part of -the -test, the truck was run over a curved -track and reverse curved -track.
After a run o-f 1100-1900 km, tires B showed detachments among the layers of the reinforcing struc-ture so that ~-the test had to be stopped. Tires A ins-tead ran with-out de-tachmen-t until the whole tread was worn.
The results obtained from all these tests demonstrate that the -tires according to -the present invention have improved performances in every sense over the o-ther test tires although the structure of the reinforcing layers at first sight may appear to be only slightly different from that of the known tires.
Although the invention has been described in detail for the purpose of illustration, it is to be understood -that such detail is solely for -that purpose and that variations can be made therein by those skilled in the art without departing from -the spirit and scope of -the invention except as it may be limi-ted by -the claims.
, .~ .
Claims (6)
1. A pneumatic tire for motor vehicles having a tread, carcass and a reinforcing structure comprising at least two layers approximately equal in width to the width of the tread which are formed by metallic cords having an ultimate elongation of about 3%, said cords being parallel to one another in each layer and crossed with respect to those of the adjacent layer, said two layers being arranged so that said cords are inclined with respect to the longitudinal direction of the tire at an angle of between 5° and 30° and in a radially outer position to said two layers at least one layer of metallic cords having a width substantially equal to that of the tread, said layer having metallic cords parallel to one another and arranged in a longitudinal direction, said metallic cords having an ultimate elongation between about 4% and about 8%.
2. The pneumatic tire of Claim 1 wherein said layer or said layers of metallic cords having an ultimate elongation between about 4% and about 8% is supported by the underlying layer of the reinforcing structure, this latter layer having a width at least equal to that of said layer or said layers of metallic cords having the said ultimate elongation, the second layer of aid reinforcing structure being inwardly graduated with respect to the first one.
3. The pneumatic tire of Claim 1 wherein said metallic cords having an ultimate elongation between about 4% and about 8% consist of cords in which the individual strands of the cord and the resulting cord are wound in the same sense.
4. The pneumatic tire of Claim 1 wherein the layer or the layers of metallic cords having an ultimate elongation between about 4% and about 8% are constituted by a single cord helically wound, with the convolutions of the helix arranged in a longitudinal direction.
5. The pneumatic tire of Claim 1 wherein the layer or the layers of metallic cords having an ultimate elongation between about 4% and about 8% are each constituted by strips placed side by side and each of said strips has a width equal to a portion of the tread width and extends longitudinally on the whole development of the tire.
6. A pneumatic tire comprising a radial carcass, a tread on the carcass, and a reinforcing structure disposed at the crown one of the carcass between the carcass and tread, said reinforcing structure comprising first and second layers of metallic cords having an ultimate elongation of about 3%, said cords being disposed at an angle of about 5°
to about 30° with the longitudinal axis of the tire, the cords of each layer being parallel to each other but the cords of the first layer being inclined in a direction opposite to the inclination of the cords of the second layer, and a third layer of metallic cords having an ultimate elongation of from about 4% to about 8% disposed radially outwardly from the first and second layers, the cords of the third layer being disposed sub-stantially parallel to each other and to the longitudinal axis of the tire, the ends of the metallic cords of one layer being joined together at a point on the circumference of the tire which is circumferentially spaced from the points where the ends of the cords of the other layers are joined.
to about 30° with the longitudinal axis of the tire, the cords of each layer being parallel to each other but the cords of the first layer being inclined in a direction opposite to the inclination of the cords of the second layer, and a third layer of metallic cords having an ultimate elongation of from about 4% to about 8% disposed radially outwardly from the first and second layers, the cords of the third layer being disposed sub-stantially parallel to each other and to the longitudinal axis of the tire, the ends of the metallic cords of one layer being joined together at a point on the circumference of the tire which is circumferentially spaced from the points where the ends of the cords of the other layers are joined.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT19019/76A IT1054931B (en) | 1976-01-05 | 1976-01-05 | IMPROVEMENT WITH RADIAL CARCASS TIRES |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1045532A true CA1045532A (en) | 1979-01-02 |
Family
ID=11153884
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA269,063A Expired CA1045532A (en) | 1976-01-05 | 1977-01-04 | Radial tire for motor vehicles |
Country Status (21)
| Country | Link |
|---|---|
| JP (1) | JPS5284610A (en) |
| AR (1) | AR209048A1 (en) |
| AU (1) | AU506874B2 (en) |
| BE (1) | BE850000A (en) |
| BR (1) | BR7700018A (en) |
| CA (1) | CA1045532A (en) |
| DE (1) | DE2659629A1 (en) |
| DK (1) | DK3877A (en) |
| ES (1) | ES225966Y (en) |
| FI (1) | FI58457C (en) |
| FR (1) | FR2337053A1 (en) |
| GB (1) | GB1567614A (en) |
| GR (1) | GR71445B (en) |
| IE (1) | IE44434B1 (en) |
| IT (1) | IT1054931B (en) |
| LU (1) | LU76515A1 (en) |
| NL (1) | NL7613701A (en) |
| NO (1) | NO144733C (en) |
| SE (1) | SE421765B (en) |
| TR (1) | TR19716A (en) |
| ZA (1) | ZA767643B (en) |
Families Citing this family (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IT1093433B (en) * | 1978-03-09 | 1985-07-19 | Pirelli | IMPROVEMENT OF THE ANNULAR STRUCTURE OF REINFORCEMENT FOR RADIAL TIRES |
| CH629142A5 (en) * | 1978-03-28 | 1982-04-15 | Semperit Ag | BELT TIRES. |
| JPS5587604A (en) * | 1978-12-26 | 1980-07-02 | Toyo Tire & Rubber Co Ltd | Radial tire |
| FR2446193A1 (en) * | 1979-01-11 | 1980-08-08 | Kleber Colombes | TIRE, ESPECIALLY FOR AIRPLANES |
| IT1125578B (en) * | 1979-10-24 | 1986-05-14 | Pirelli | IMPROVEMENT OF STRENGTH ANNULAR STRUCTURES FOR RADIAL TIRES |
| FR2473426A1 (en) * | 1979-12-06 | 1981-07-17 | Dunlop Ltd | PNEUMATIC HAVING A REINFORCING BELT, IN PARTICULAR FOR HEAVY WEIGHT |
| DE3108140A1 (en) * | 1981-03-04 | 1982-09-16 | Continental Gummi-Werke Ag, 3000 Hannover | Pneumatic vehicle tyre |
| JPS6082409A (en) * | 1983-10-14 | 1985-05-10 | Bridgestone Corp | Radial tire |
| JPS6082407A (en) * | 1983-10-14 | 1985-05-10 | Bridgestone Corp | Radial tire for heavy car |
| JPS61192433U (en) * | 1985-01-28 | 1986-11-29 | ||
| JP2742310B2 (en) * | 1989-11-30 | 1998-04-22 | 住友ゴム工業 株式会社 | Radial tires for passenger cars |
| CA2100538A1 (en) * | 1992-10-21 | 1994-04-22 | Johnny Dale Ii Massie | Cut resistant tire |
| US6619357B1 (en) | 2002-04-24 | 2003-09-16 | The Goodyear Tire & Rubber Company | Belt package for super single truck tires |
| US7267149B2 (en) | 2003-12-22 | 2007-09-11 | The Goodyear Tire & Rubber Company | Pneumatic tire with improved crown durability |
| US7503363B2 (en) | 2005-03-30 | 2009-03-17 | The Goodyear Tire & Rubber Company | Belt package for super single truck tires |
| US7490648B2 (en) | 2005-03-30 | 2009-02-17 | The Goodyear Tire & Rubber Company | Belt package for super single truck tires |
| US9168789B2 (en) | 2008-12-19 | 2015-10-27 | The Goodyear Tire & Rubber Company | Truck tire |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4732321U (en) * | 1971-04-20 | 1972-12-12 | ||
| IN139798B (en) * | 1972-08-18 | 1976-07-31 | Uniroyal Inc |
-
1976
- 1976-01-05 IT IT19019/76A patent/IT1054931B/en active
- 1976-12-09 NL NL7613701A patent/NL7613701A/en not_active Application Discontinuation
- 1976-12-17 GB GB52910/76A patent/GB1567614A/en not_active Expired
- 1976-12-23 ZA ZA767643A patent/ZA767643B/en unknown
- 1976-12-24 AU AU20936/76A patent/AU506874B2/en not_active Expired
- 1976-12-28 JP JP16084676A patent/JPS5284610A/en active Granted
- 1976-12-28 FR FR7639238A patent/FR2337053A1/en active Granted
- 1976-12-30 AR AR266055A patent/AR209048A1/en active
- 1976-12-30 BE BE173756A patent/BE850000A/en not_active IP Right Cessation
- 1976-12-30 DE DE19762659629 patent/DE2659629A1/en not_active Withdrawn
-
1977
- 1977-01-03 SE SE7700039A patent/SE421765B/en unknown
- 1977-01-03 TR TR19716A patent/TR19716A/en unknown
- 1977-01-04 CA CA269,063A patent/CA1045532A/en not_active Expired
- 1977-01-04 LU LU76515A patent/LU76515A1/xx unknown
- 1977-01-04 ES ES1977225966U patent/ES225966Y/en not_active Expired
- 1977-01-04 NO NO770006A patent/NO144733C/en unknown
- 1977-01-04 GR GR52516A patent/GR71445B/el unknown
- 1977-01-04 BR BR7700018A patent/BR7700018A/en unknown
- 1977-01-04 FI FI770013A patent/FI58457C/en not_active IP Right Cessation
- 1977-01-05 IE IE20/77A patent/IE44434B1/en unknown
- 1977-01-05 DK DK3877A patent/DK3877A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| FR2337053B1 (en) | 1979-09-28 |
| BE850000A (en) | 1977-04-15 |
| GB1567614A (en) | 1980-05-21 |
| ES225966U (en) | 1977-03-16 |
| ZA767643B (en) | 1977-11-30 |
| LU76515A1 (en) | 1977-06-14 |
| NO770006L (en) | 1977-07-06 |
| FR2337053A1 (en) | 1977-07-29 |
| DK3877A (en) | 1977-07-06 |
| GR71445B (en) | 1983-05-18 |
| FI770013A (en) | 1977-07-06 |
| DE2659629A1 (en) | 1977-07-14 |
| JPS5284610A (en) | 1977-07-14 |
| NL7613701A (en) | 1977-07-07 |
| SE7700039L (en) | 1977-07-06 |
| JPS578724B2 (en) | 1982-02-18 |
| IT1054931B (en) | 1981-11-30 |
| NO144733C (en) | 1981-10-28 |
| BR7700018A (en) | 1977-09-06 |
| FI58457C (en) | 1981-02-10 |
| IE44434B1 (en) | 1981-12-02 |
| AR209048A1 (en) | 1977-03-15 |
| AU506874B2 (en) | 1980-01-24 |
| NO144733B (en) | 1981-07-20 |
| AU2093676A (en) | 1978-06-29 |
| ES225966Y (en) | 1977-07-16 |
| IE44434L (en) | 1977-07-05 |
| TR19716A (en) | 1979-10-16 |
| SE421765B (en) | 1982-02-01 |
| FI58457B (en) | 1980-10-31 |
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