Stone working – Sawing
Reexamination Certificate
2000-01-19
2002-10-29
Eley, Timothy V. (Department: 3723)
Stone working
Sawing
C451S451000
Reexamination Certificate
active
06470874
ABSTRACT:
BACKGROUND
The present invention generally relates to concrete saws, specifically to high production concrete saws, and particularly to riding concrete saws.
When concrete roads are poured, they must be cut within a certain time frame. It is a known fact that concrete will begin to crack as it hardens. The objective of the saw cut is to get the concrete to crack where you want it to along control joints. When the concrete cracks, it finds the path of least resistance, which happens to be the saw cut. There are dowel bars or other expansion devices buried in the concrete. The saw cuts are perpendicular to these bars. Thus, after cracking along the saw cuts, the slab now becomes independent pads. The dowel bars allow the independent pads to expand and contract without losing alignment.
When sawing concrete, water is used as a coolant. The fine particles created by the smooth sawing (grinding) of concrete create a mixture called slurry. The slurry is very abrasive. When the water evaporates from the slurry, it once again solidifies into a hard substance.
Concrete saws historically rotate in a downward (clockwise) direction and discharge slurry rearward or in other words in an opposite direction to the forward direction of travel. For joint sawing and widening, it is desirable to discharge the slurry in a forward direction known as up-cutting or counterclockwise rotation so the joint does not fill with slurry. Slurry must be flushed out of joints before it begins to set up. The rotating forces of the up-cutting rotating blade help throw the slurry forward and out of the joint being cut. One reason it is not desirable for other applications is that slurry being discharged forward will cover the string line and the operator will have difficulty sawing straight. The primary reason for down cutting over up-cutting is the forces of the up-cutting action tend to lift the rear of the saw. This leads to poor traction and control, once again making it very difficult to saw consistently and straight.
One solution to lifting the rear of the saw by the upcutting action is adding weight. Since conventional saws are manually turned, weight and size are major factors. The riding saw concept permits a larger and heavier machine to overcome this traction problem. For this reason, an upcut saw is now productive in a riding saw.
It can be appreciated that sawing concrete involves the transfer of high torque from the power source (motor) to the saw blade. Because of the high torque requirements, belt drives are preferred for their cost and reliability over other types of drive systems such as hydraulic or gear drives. It can be appreciated that the belts transfer power through friction between the belt and the pulley, with the area of contact of the belt with the pulley being a major factor in the amount of friction and thus of power transfer. Further, the larger the pulley, the more belt wrap and contact with the pulley. However, on concrete saws, the pulley diameter is kept to a minimum so the blade diameter can also be as small as possible. As an example, if the pulley diameter is 6 inches (15 cm) and the blade is 12 inches (30 cm), the maximum cutting depth is 3 inches (12.5 cm). Since diamond blades are so expensive, controlling the pulley size is critical.
Conventional engines rotate clockwise when viewing the flywheel or output end. On conventional down-cut saws, this places the belt drive on the opposite end of the dirty sawing side of the saw. (Sawing is always done on the right side of the machine as all the controls are configured for same side sawing.) When the riding saws evolved and if conventional clockwise rotating engines are utilized, it was necessary to have the operator sit on the opposite side of the machine to place the belt drive on the opposite end of the dirty sawing side of the saw, which is unacceptable. This is so because the air intake of the engine is on that side and the contaminants would be sucked into the engine (unless an elaborate, costly air-intake systems could be designed). It is also customary to saw from the right side and operators will be uncomfortable when switching between the riding and walk-behind saws. Also, the intake side of the engine is very large in comparison to a 6 inch (15 cm) diameter output pulley. Since the operator saws via sight of the blade, the engine and the air-intake system would greatly reduce vision.
To overcome these problems in riding concrete saws, the engine was rotated 180 degrees. This places the belts on the same side as the saw blade. The belts are now exposed to all of the contaminates generated from the sawing action. Particularly, while sawing, some of the slurry gets into the belt and pulley system. The abrasive material starts grinding away at the steel grooves like a polishing compound. As the pulley grove V profile is altered, the ability of the V-belt to transfer HP is diminished (the V-belt transfers power through friction between the belt and groove).
As the belts begin to slip after exposure and wear, the natural operator reaction is to tighten the belts tighter. The current designs use a pivoting platform with an adjustment on each side. Bolts at two adjustment points on opposite sides of the plate are used to keep the two belt pulleys parallel for maximum HP transfer. As these bolts are extended, the platform rotates and the belts are tensioned. If these two adjustment points are not adjusted uniformly, which occurs often, the drive pulleys are no longer parallel. This is a big problem since the horsepower is being transferred in such a narrow space. It also creates uneven wear on the belts and pulleys.
All these factors combined forces the operator to keep over-tensioning the drive system. This eventually exceeds the overhung load capacity of the engine and causes premature engine crankshaft failure. This is a serious problem due to downtime and expense of major engine repairs.
It should be appreciated that the power source for the concrete saw must be able to operate in the dirty environment, must produce maximum power, and must be of a small size so that the saw can be compact and maneuverable. Non-liquid cooled, high torque diesel engines are a preferred form of power source, but the only such engine currently on the market has been susceptible to crankshaft failures due to excessive working loads. To overcome this problem, outboard bearings have been utilized such as suggested in U.S. Pat. No. 4,787,678. But outboard bearings make replacement of belts time consuming. Thus, it is preferred that the engine pulley be supported solely by inboard bearings as has been previously performed by the CIMLINE manually turned concrete saws.
Thus, a need continues to exist for high production concrete saws which overcome the problems and deficiencies of existing concrete saws and which provide synergistic results and advantages in the field of concrete saws.
SUMMARY
The present invention solves this need and other problems in the field of concrete saws by providing, in the preferred form, an operator platform which is elastomerically isolated from the chassis by a plurality of elastomer cushions sandwiched between a seat base and a mount. A seat, a footrest, and an armrest are each mounted to the mount, and a control joystick is mounted relative to the armrest. In the most preferred form, the operator platform and the saw blade are mounted outwardly of the rails of the chassis, with a plane defined by the saw blade extending through the operator platform.
In the preferred form where the saw blade is belt driven by a sheave located on a shaft intermediate the saw blade and the frame, a guard is provided having a housing including a U-shaped, axially extending wall closely conforming to the sheave. A seal rotatably receives the shaft and is within a radially extending panel extending across the outer edge of the U-shaped wall. A tongue extends across the inner edge of the U-shaped wall. In the most preferred form, the guard further includes a second housing having a U-shaped, axially extending wall extending around the dri
Cimline Inc.
Eley Timothy V.
Nguyen Dung Van
LandOfFree
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