Stone working – Sawing – Endless
Reexamination Certificate
1999-12-13
2001-02-13
Morgan, Eileen P. (Department: 3723)
Stone working
Sawing
Endless
C451S444000, C451S453000, C451S298000
Reexamination Certificate
active
06186136
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to chain saws used for cutting concrete and more particularly to a system for removing expended slurry from the cutting components.
BACKGROUND OF THE INVENTION
Concrete cutting chain saws are basically structured like conventional chain saws in that a power head drives a sprocket, a bar is mounted to the power head in alignment with the sprocket, and a loop of cutting chain is entrained around the bar and sprocket to be rapidly driven by the sprocket in a circuitous path. Projecting teeth from the saw chain sequentially bite into a surface being cut, each removing small bits of material and collectively cutting a kerf through the material.
The chain consists of numerous individual parts including cutting teeth, side links and center links primarily made of steel and in the case of a concrete saw, the teeth of the cutters have embedded diamond bits. Whereas wood products i.e., trees, are commonly cut with chain saws with a chain lasting for many hours, days and weeks of cutting, as concerns concrete cutting, the cutting chain rapidly wears and has to be frequently replaced at great expense.
A known cause of this rapid wearing is the presence of concrete dust or small particles of concrete that are immersed in water and which form a slurry. The particles in the slurry become injected into the bearing surface areas of the chain. A saw chain is made of many individual links that are interconnected for relative pivoting. Holes formed in the links are aligned fore and aft with holes in preceding and succeeding links, and pins or rivets projected through the holes connect the links together so as to allow relative pivoting. This pivotal action which occurs continuously as the chain is driven around the sprocket and bar produces surface to surface rubbing as between the rivets and the rivet holes for example. Due to the concrete particles being injected between these surfaces, the wearing of the surfaces increases significantly and this wearing induces stretching of the chain as the holes are enlarged. The chain needs to be taut and as it stretches, the chain mount has to be adjusted and such is time consuming. Eventually the chain stretches to a point where it no longer meshes with the drive sprocket and has to be replaced. This often occurs prior to total wearing of the cutting teeth which is normally expected to determine end of life.
It is an object of the present invention to reduce the rate of wearing caused by concrete slurry being injected into the saw chain pivotal joints.
BRIEF SUMMARY OF THE INVENTION
Studies were conducted and it was determined that significant amounts of the slurry are carried by the rapidly running chain as the chain enters the housing of the drive sprocket end of the bar. It is theorized that this housing or enclosure entraps the slurry and the chain functions like an impeller to carry the slurry into and through the housing at the rear end of the bar where the slurry becomes concentrated. Because the chain is forced to pass through the area of concentration, the slurry has a greater propensity to penetrate into the pivotal joints with the undesired wearing being a result.
Prior to this invention the housing portion enclosing the drive sprocket and bar end (sometimes referred to as a cowel or cowling) was slotted below the sprocket with the idea that the slurry would, by gravity action, be directed down through the slots. The amount of slurry falling away from the chain and down through the slots was minimal and the present invention is directed to an alternative solution to the problem.
It is theorized that the flow of slurry follows the path of the chain and is somewhat tumultuous as the various forces act to direct the slurry in a cicuratious path around the drive sprocket. Least of these is gravity force which is greatly exceeded by the force of momentum and centrifugal force, and thus there is little chance for the slurry to fall down through the slots.
In the preferred embodiment of the invention, a diverter in the form of barriers or deflectors, e.g., baffles, are placed in the flow path of the slurry. These deflectors (baffles) are placed in the cowel or as part of the cowel in the area whereat the chain enters the drive sprocket. Preferably they are located in the area where the chain travels around the sprocket and particulary within the 90 degree turn where the chain is being reversed, i.e., at the rearmost point of travel. The baffles are positioned in close proximity to the travel path of the saw chain as it travels around the sprocket and preferably they are oriented radially with respect to the sprocket. In this orientation, the slurry impacts and is deflected off the baffles toward the bottom of the cowling.
The baffles are enclosed by the cowling to form a catch basin and the basin is provided with a drain hole or holes. As the slurry flows into the cowel and as the chain starts its turn around the sprocket, the slurry flows against the baffles and is diverted by the baffles into the basin whereat the slurry settles and flows down through the drain holes.
As a second part of the invention, just prior to the saw chain entering onto the drive sprocket, a water nozzle is provided on the housing at a position that is at the inner side of the chain (inside the chain loop), the nozzle being directed, inside to outside through the chain. Water forced through the nozzle flushes slurry from the chain and into the path of the slurry being otherwise propelled by the chain teeth where it will engage and be deflected by the baffles, thus cleansing the chain before the joints start to articulate as required to change direction from straight line travel to curved travel and back to straight line travel at the top of the sprocket.
The combination of the flushing nozzle and flow-deflecting baffles produces substantially increased removal of the slurry. Tests have been conducted and the removal of the slurry has improved the wearability of the chain pivotal joints achieving as much or more than 30% increased life. Furthermore, it has been found that the life of the cutting teeth is increased which is believed due to the additional flushing or cleansing of the teeth by the above added water nozzle.
The invention and the benefits therefrom will be more fully understood and appreciated with reference to the following detailed description and drawings referred to therein.
REFERENCES:
patent: 3593700 (1971-07-01), McNulty
patent: 4920947 (1990-05-01), Scott et al.
patent: 5184598 (1993-02-01), Bell
patent: 5215072 (1993-06-01), Scott
patent: 5603311 (1997-02-01), Hoerner et al.
patent: 5918586 (1999-07-01), Von Dungen et al.
patent: 3413513 (1985-03-01), None
Blount, Inc.
Harrington Robert L.
Morgan Eileen P.
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