Resilient tires and wheels – Tires – resilient – Anti-skid devices
Reexamination Certificate
1998-09-09
2001-01-30
Maki, Steven D. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Anti-skid devices
C152S209240
Reexamination Certificate
active
06179027
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a pneumatic tire, and more particularly to an agricultural pneumatic tire comprising a tread provided with many directional slant lugs extending from a central portion of the tread toward both ends of the tread in a direction inclined with respect to a circumferential direction of the tire and alternately arranged right and left with respect to an equatorial plane of the tire at given intervals in the circumferential direction of the tire.
2. Description of Related Art
There have hitherto been proposed and practiced many agricultural pneumatic tires each comprising a tread provided with many directional slant lugs extending from a central portion of the tread toward both ends of the tread in a direction inclined with respect to a circumferential direction of the tire and alternately arranged right and left with respect to an equatorial plane of the tire at given intervals in the circumferential direction of the tire in order to ensure running performances such as traction performance, running performance and the like when the tire is run on muddy road or soft road.
Throughout the specification, the term “directional slant lugs” means lugs obliquely extending with respect to the circumferential direction and forming so-called directional tread pattern designating a rotating direction (forward running direction) RD when the tire is mounted onto a vehicle that an obliquely extended portion of the lug located at a side near to the equatorial plane first contacts with ground and the lug portion located far from the equatorial plane contacts with ground later, and a front side of the lug first contacting with ground in the forward running direction of the tire is “stepping-in side of the lug” and a rear side of the lug later contacting with ground in the forward running direction of the tire is “kicking-out side of the lug”.
In such an agricultural pneumatic tire, the traction performance and mud splashing property are required as an important performance when the tire is run on muddy road or soft road. In order to decrease mud clogging on the muddy road, it is effective to widen a circumferential interval between the lugs arranged in the tread, but as the interval between the lugs becomes wider, ride comfortability against vibrations when the tire is run on general road are undesirably degraded.
On the other hand, as a lug forming angle or an angle of the lug inclined with respect to a direction parallel to an axial direction of the tire becomes small, the traction component becomes large, but the fluidity of mud between the lugs becomes small and the mud clogging is liable to be caused.
SUMMARY OF THE INVENTION
Under the above situation, it is an object of the invention to provide an agricultural pneumatic tire having excellent traction performance and mud splashing property in the running on muddy road or soft road and an excellent ride comfortability against vibrations in the running on general road.
According to the invention, there is the provision of an agricultural pneumatic tire comprising a tread provided with many directional slant lugs extending from a central portion of the tread toward both ends of the tread in a direction inclined with respect to a circumferential direction of the tire and alternately arranged right and left with respect to an equatorial plane of the tire at given intervals in the circumferential direction of the tire, wherein (1) said lugs are directional slant lugs forming so-called directional tread pattern designating a rotating direction (forward running direction) RD when the tire is mounted onto a vehicle that an obliquely extended portion of the lug located at a side near to the equatorial plane first contacts with ground and the lug portion located far from the equatorial plane contacts with ground later; (2) a side wall at a stepping-in side of the lug consists of a flat face slanted at an angle &agr; of 30-45° with respect to a face inclusive of a rotating axis of the tire in a region ranging from an outer surface of the lug to a position of a height h corresponding to 45-75% of a lug height H viewed at circumferential section perpendicular to the surface of the tread, and a bored face formed in a region ranging from an end of the flat face toward a root of the lug; (3) a side wall at a kicking-out side of the lug is a flat face slanted at an angle &bgr; of 0-22° with respect to a face inclusive of a rotating axis of the tire viewed at circumferential section perpendicular to the surface of the tread; (4) a lug forming angle &ggr; defined by an angle of a straight line connecting an end at the stepping-in side of the lug located near to a central portion of the tread to an end at the stepping-in side of the lug located near to each end of the tread with respect to a direction parallel to an axial direction of the tire is 30-40°; and (5) a ratio of circumferentially overlap component L
2
of the lugs arranged right and left with respect to an equatorial plane of the tire to circumferential length component L
1
of the lug is 30-60%.
In general, as the lug forming angle &ggr; defined by an angle of a straight line connecting an end at the stepping-in side of the lug located near to a central portion of the tread to an end at the stepping-in side of the lug located near to each end of the tread with respect to a direction parallel to an axial direction of the tire becomes small, the traction component becomes large, but the fluidity of mud between the lugs is decreased and hence the mud clogging is apt to be caused. On the other hand, as the lug forming angle &ggr; becomes large, mud is easily fluidized between the lugs and the mud clogging is favorably prevented, but the distance from the end at the stepping-in side of the lug located near to the central portion of the tread to the end at the stepping-in side of the lug located near to each end of the tread or the lug length becomes long, so that it can not necessarily be said that the increase of the lug forming angle &ggr; is favorable in the prevention of the mud clogging.
The agricultural pneumatic tire according to the invention has the above construction, particularly a feature that the lug forming angle &ggr; defined by an angle of a straight line connecting an end at the stepping-in side of the lug located near to a central portion of the tread to an end at the stepping-in side of the lug located near to each end of the tread with respect to a direction parallel to an axial direction of the tire is 30-40°, so that the fluidity of mud between the lugs is easy and the mud clogging hardly occurs and the excellent traction performance is developed while matching with various soil conditions.
In the agricultural pneumatic tire comprising a tread provided with many lugs as mentioned above, when the tire is run forward on soil, the side wall of the lug at the stepping-in side enters into the soil and is subjected to reaction force from the soil to create traction force in the forward running direction. The magnification of the reaction force is determined by an angle of the side wall when the lug enters into the soil, while this angle differs in accordance with subsidence depth of the tire. Considering that the tilling depth is usually 20-40 cm, best results are obtained when the side wall of the lug at the stepping-in side is formed by a flat face inclined at an angle &agr; of 30-45° with respect to a face inclusive of the rotating axis of the tire. On the other hand, when the lug gets out from the soil during the running of the tire, there may be caused the carrying of soil. In order to lessen such a carrying of soil, the side wall of the lug at the stepping-in side is formed by a flat face inclined at an angle &agr; of 30-45° with respect to a face inclusive of the rotating axis of the tire likewise the above case.
Considering only the function when the lug enters into soil or gets out from soil, the side wall of the lug at the stepping-in side may be formed by the flat face having an inclination angle &agr;
Bridgestone Corporation
Maki Steven D.
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
Agricultural pneumatic tires having directional lugs does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Agricultural pneumatic tires having directional lugs, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Agricultural pneumatic tires having directional lugs will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2439018