Stone working – Sawing – Reciprocating
Patent
1992-05-20
1993-08-10
Rose, Robert A.
Stone working
Sawing
Reciprocating
125 14, 125 1603, B28D 106, B28D 126
Patent
active
052339688
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns a percussion sawing machine to saw stone blocks into slabs. As known, these machines essentially consist of a fixed part, acting as support, and of a movable part which comprises the oscillating blade frame.
The fixed part consists of a stout framework comprising four vertical steel columns, fixed at the bottom to a reinforced concrete foundation and connected at the top by four steel cross members. A large worm screw is positioned inside each vertical column and the four screws are caused to rotate simultaneously by suitable motor means. Each screw then carries, in a screw-and-nut relationship, a corresponding lead nut to which is fixed the movable part of the sawing machine.
The movable part essentially consists of a horizontal rectangular blade frame, into which is fixed a set of parallel and suitably tensioned saw blades, consisting of steel plates having a scarcely thick rectangular cross section. The dimensions of the blade frame are substantially equal to the inner dimensions of the fixed part of the sawing machine, into which said frame oscillates moving simultaneously downwards so as to perform the cutting of the block into slabs.
In the sawing technique making use of the aforedescribed machines, the steel blades of the blade frame simply have the function to apply the actual stone cutting medium, which consists of a thick slurry of water and abrasive material. Said slurry is constantly circulated over the stone block being cut by a suitable pump positioned into a tank provided under said stone block, wherein the slurry is collected. Different types of abrasive material are of course used, according to the kind of stone block being cut: sand has traditionally been used for sawing marbles, whereas a mixture of steel grit and lime is adopted for granites. The slurry is periodically or continuously reactivated by adding fresh abrasive material, so as to make up for that consumed in the cutting operation.
In all the sawing machines adopted at present, the oscillating movement of the blade frame is of the hunting type, obtained by fixing said frame to the fixed part of the machine by means of four rocking arms connected--freely rotatable by way of hinged joints--by one end to the four corners of said blade frame and by their opposite end to the previously cited lead nuts.
With this type of construction, during the alternate huntings of the blade frame each point of the single saw blades describes a circle arc trajectory, of radius equal to the length of the rocking arms and of maximum chord (commonly called "travel") equal to twice the length of the crank of the connecting rod-crank system imparting the alternate motion to the blade frame. The effective part of this travel, namely that in which the abrasive cutting action actually takes place, is obviously only that in which the blades are in contact with the stone block to be cut, being therefore--from a theoretical point of view--only the central point of the hunting travel. In the remaining part of their travel, the blades rise from the bottom of the respective channels cut into the stone block, allowing a further essential function of the sawing machine to be performed, namely the outlet from the cutting channels of the consumed slurry and the simultaneous feeding of fresh slurry required for the sawing operation.
In actual fact, the effective contact length between the blades and the block being cut is far longer and, taking also into account the partial deflection of the blades tensioning system while they bear onto said block, the average values of the contact length are equal to 30-35% of the travel, in sawing machines having rocking arms about 1 meter long. Said value--also known as abrasion ratio--directly answers for the sawing speed and thus for the productivity of the machine.
2. Description of the Prior Art
Numerous studies have been carried out since several years and different solutions have been proposed to rise said abrasion ratio beyond the aforespe
REFERENCES:
patent: 10844 (1887-06-01), Foerster
patent: 1347365 (1920-07-01), Fletcher
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