Wheel substitutes for land vehicles – Tracks or treads – With detachable grouser for endless chain track
Reexamination Certificate
2001-12-04
2002-11-12
Morano, S. Joseph (Department: 3617)
Wheel substitutes for land vehicles
Tracks or treads
With detachable grouser for endless chain track
C305S019000, C305S111000, C152S22500R
Reexamination Certificate
active
06478389
ABSTRACT:
TECHNICAL FIELD
This invention relates to tire chains. More particularly, the present invention relates to tire chains used on compact front-end loaders and other similar construction machinery to improve floatation, traction, and handling during operation.
BACKGROUND OF THE INVENTION
For many years cars, trucks, and other tire mounted vehicles have used tire chains to improve operational control over soft or slippery road surfaces.
A. Skid Steer Loaders
More recently, construction machinery owners have attempted to use tire chains on tire mounted construction machines. This is especially true for compact front-end loaders, which will be referred to as skid steers. Skid steers are powerful compact loaders used to dig, haul, or lift earth and other materials. The main components of skid steer loaders include an operator's cab, a diesel or gasoline engine, hydraulic pumps, hydrostatic transmission, a pair of lift arms, a bucket operatively attached at the 25 distal ends of the lift arms, and two pairs of opposing tires. Many other construction machines and vehicles are composed of similar components. What separates the skid steer from its counterpart construction machinery is its unique steering system.
B. Steering Systems
Front-wheel steering is a popular directional steering system used on tire-mounted vehicles such as cars and trucks. A car usually steers or turns by changing the direction of the front tires. Turning occurs because while being in motion the centerline of the front tires is no longer parallel or in line with the centerline of the rear tires. Similar concepts, e.g. rear-wheel and all-wheel steering, can be seen in typical forklifts.
Many tire-mounted construction machines use articulated directional steering. Articulated steering works because the vehicles are designed in two separate independent sections. The two sections are connected at a pivotal point. Whenever the two sections pivot and their centerlines point in different (unparallel) directions, the vehicle turns. Articulated steering can be seen in most front-end loaders over 10,000 pounds.
C. Steering System for Skid Steer Loaders
The skid steer loaders use a directional steering system. In skid steers, the centerlines of the front and rear tires remain parallel and in line with each other at all times. This kind of steering system can be also seen in excavators, bulldozers and tanks, and is one of the very few steering systems that allow the vehicle to turn 360 degrees without moving forward or backward.
The directional steering capabilities of a skid steer arises from the independent pairs of left and right side drive systems. Tire-mounted skid steers have four axles, two per side of the machine. The two axles per side are spaced typically 3 feet to 4 feet apart on the same lateral axis and evenly protruding from the machine body. Identical wheels and tires are mounted on each of the axles. A key factor for the turning capabilities of skid steer loaders is that the left and right pairs of opposing tires are powered by independent drive systems. As a result, when the left and right pairs of opposing tires are moving forward at the same speed, then the machine moves straight forward. However, if the left pair of tires is moving forward at a different speed than the right pair of tires, then the loader will slide and turn. The machine turns in the direction of the side with the faster moving pair of tires. Moreover, if the left pair of tires is moving forward and the right pair of tires is moving backward, or vice versa, at the same speed, then the skid steer performs a 360-degree rotation without moving forward or backward. Since all four Skid steer tires remain parallel and in line to each other at all times, tire chains can be utilized more efficiently to improve floatation, traction and control.
D. Applying Tire Chains to Skid Steers In the last decade, the skid steer has become a very popular machine in the construction industry. It has won recognition for being a versatile machine (for example, being the construction vehicle with a great variety of attachments), and a compact and maneuverable machine that can handle many types of construction jobs. However, occasionally the tires of the skid steer tend to slip, especially in snow, mud, sand, and other slippery or boggy conditions that are often found on job sites. The insufficient traction of the four skid steer tires under certain conditions results in unsatisfactory and often risky operation and performance. In an attempt to resolve this, tire chains have been applied to skid steers.
When cars or trucks use tire chains, each tire must use its own chain, the so-called “single-wheel” tire chain. Due to the unique steering system of the skid steer—all wheels remaining parallel and in line with each other at all times—a more advanced tire chain can be used. The skid steer “two-wheel” tire chain is wrapped around each pair of left and right side tires. The two-wheel tire chain is more efficient because more chain is making contact with the operating ground. The whole area between the two tires on each side of the machine (usually 3 to 4 feet) is used for additional traction and floatation. This feature of the skid steer two-wheel tire chain is in sharp contrast to the single-wheel tire chains, which utilize only the operating ground that is immediately under the tire. Depending on the spread of the wheelbases of the skid steer, the contact area between the operating ground and the two-wheel tire chain can be on average 5 to 10 times greater than that of the single-wheel tire chain.
E. Current Tire Chains for Skid Steer
Current tire chains made for skid steers attempt to solve the problem with traction insufficiency under slippery or boggy operating ground conditions. The main component of the current skid steer two-wheel tire chains is the “pad.” The pad usually consists of a crossbar with two opposing sidewalls —one on each side of the crossbar. The sidewalls, which are set perpendicular to the connecting crossbar, create a valley or groove. When subsequent pads are connected together with links to comprise a chain, a continuous groove is formed for skid steer tires to ride within. The sidewalls of each pad keep the chain aligned with the tires and at the same time prevent the tires from derailing off the chain.
F. Drawbacks of Current Two-Wheel Tire Chains for Skid Steers
Current two-wheel tire chains for skid steers generally work mechanically well. However, these tire chains provide poor enhancement to the traction of the loader machine in slippery or boggy conditions and offer little or no floatation. The term “floatation” refers to the wheels and chains of the loader remaining above the ground surface, rather than sinking into the ground during operation of the skid steer. For the optimal performance of the skid steer, both problems of traction and floatation have to be resolved simultaneously. In addition to the traction and floatation problems, the current two-wheel tire chains for skid steers impose many other inconvenient restrictions that need consideration.
One drawback is that current skid steer two-wheel tire chains have a large open space between adjacent pads and between the two crossbars of each individual pad. The open spaces between adjacent pads and between the crossbars of the single pads limits both traction and floatation of the loader. For example, when operating the skid steer in mud, the open spaces within the chain allow the mud to pass upwards. This causes the machine to sink, and creates extreme operating stresses for the drive motors. Indeed, skid steers using the current two-wheel tire chains in mud have to deal with a greater drive motor pressure than not having a chain at all, since the bare tires tend to spin in the mud, while the skid steers with current chains sink into mud. Traction is also lost due to the open spaces. When the chains move and push the mud, the mud simply moves over the crossbars of the pads. When the machine tries to move forward in the mud, the chains whip and mix the mud, instead of effec
Bellinger Jason H.
Morano S. Joseph
Trojan Law Offices
LandOfFree
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