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Tie-rod for stone materials sawing machinery

DESCRIPTION

The present invention relates to a tie-rod for stone material for stone materials sawing machinery, in particular stone materials in the form of blocks, in order to produce slabs .

For many years machines, known as gangsaws, have been used for sawing stone materials, comprising essentially a support structure formed by four angular columns with, mounted thereon, two assemblies with oscillating arms, movable vertically along the columns; a horizontal so-called blade-holder unit is mounted on the bottom ends of the arms . Blocks of stone material to be sawn are arranged underneath the blade-holder unit . .

In order to perform the sawing of stone material , the blade-holder unit is made to perform an oscillating movement imparted by the oscillating arms. As the blades cut the stone material and the cutting depth increases, the support structure moves downwards along the columns, so as to allow gradual cutting of the entire block of stone material until a predefined limit height is reached.

The oscillating movement of the arms is provided by a connecting rod and crank mechanism, operation of which is performed by means of a motor-driven flywheel actuated by an electric drive .

Each blade-holder unit, which has a substantially rectangular form, is composed, on two opposite sides, of two sections or large plates between which a plurality of sawing blades made of ferrous material

(normally consisting of a number varying from 100 to

200) are mounted, said blades being parallel to each other and at a relative distance varying from a few millimetres to a few centimetres and spaced from each other by means of spacers also said "troccoletti" : each blade is fixed on two opposite sides of the gangsaw by means of fastening elements called tie-rods, referred to as "connecting-rod side tie-rod" and "tensioner side tie-rod" ; the latter also perform the function of tensioning components, so as to keep the blade under a predetermined tension.

The most common method of fastening the blades to the blade-holder unit and therefore performing fixing to the aforementioned tie-rods envisages a first end of each blade seated in a bracket, the latter forming the end of the tie-rod, and secured in the bracket by means of a transverse pin which engages with the holes aligned axially and provided in the terminal portion of the blade and in the two flanges of the bracket between which the aforementioned end of the blade is inserted. The transverse pin, which ensures fixing together of the blade and tie-rod, usually has a circular cross- section and cylindrical form.

Since the sawing gangsaw is made to perform an oscillating movement, the sawing blades wear rapidly and their wear has a progression which is entirely particular; the bottom edge of the blade, namely the cutting part of the blade, is prone to considerable wear of the material in the central portion even after a few working cycles . As the blade becomes worn, the tractional forces applied to the two ends of the blade are transmitted solely onto the top portion of the blade, so that the

latter is no longer perfectly tensioned and tends to bow and also rotate about the two fixing pins with a circular cross-section and cylindrical form, and wear of the central portion of the blade is consequently accentuated, causing a poor sawing action.

It is obvious, therefore, that fixing of the blade to the tie-rod by means of the pin which has a circular cross-section and cylindrical form is not convenient at all. For this reason, the Applicant developed a blade and tie-rod assembly for stone material sawing machinery having pins with a cross-section which is not circular, according to the subject of Italian patent application No. LU2003A00005. The assembly allows tighter fastening of the tie- rod and blade which ensures a smaller degree and more uniform wear of the blade owing to the fact that the blade is unable to rotate with respect to the tie-rod. It is known, however, that, during the course of the sawing operation, the wear of the blades occurs in relatively short periods of time so that replacement with new blades must be performed frequently: if it is considered that each blade has a length of about 3-5 metres and that every time it is required to disassemble 100 to 200 blades and replace the worn blades with the same number of new blades (each of which must also be tensioned again) , it is clear that this operation involves a considerable amount of downtime which obviously affects productivity and consequently the profitability of the industrial process in question.

The technical problem of the present invention is

to provide an improved tie-rod which ensures faster replacement of the worn blades as well as a stability of the blade/tie-rod assembly which is not dependent on the cross-section of the connection pin, overcoming in this way the drawbacks associated with the solutions of the prior art .

The technical problem is solved by a tie-rod for fixing a blade to a gangsaw for sawing stone material , characterized in that it comprises a body associated with a head portion in turn comprising at least one fixed pin, the latter being able to receive the blade provided with at least one corresponding hole having a shape compatible with that of the at least one first fixed pin, the head portion also comprising fixing means for engagement with said body.

The characteristic features and advantages of the invention will emerge from the description, provided hereinbelow, of an example of embodiment thereof provided by way of a non-limiting example with reference to the accompanying drawings in which:

- Figure 1 shows a top plan view of a tie-rod, according to a first embodiment of the invention;

- Figure 2 shows a side view, in the direction of the arrows, of the tie-rod according to Figure 1; - Figure 3 shows a top plan view of a blade/tie- rod system according to a first embodiment of the invention;

- Figure 4 shows a side view, in the direction of the arrows, of the blade/tie-rod system according to Figure 3;

Figure 4b shows a perspective view of a blade/tie-rod system according to the invention;

- Figure 5 shows a top plan view of a blade/tie- rodsystem in accordance with a second embodiment of the invention;

- Figure 6 shows a side view, in the direction of the arrows, of the blade/tie-rod system according to

Figure 5 ;

- Figure 7 shows a top plan view of a blade/tie- rod/tensioner system;

- Figure 8 shows a side view, in the direction of the arrows, of the blade/tie-rod/tensioner system according to Figure 7 ;

- Figure 9 shows top plan view of a variant of the blade/tie-rod/tensioner system according to Figure 7 ;

- Figure 10 shows a side view, in the direction of the arrows, of the blade/tie-rod/tensioner system according to Figure 9 ;

- Figure 11 shows a top plan view of a variant of the blade/tie-rod/tensioner system according to Figure 9; - Figure 12 shows a side view, in the direction of the arrows, of the blade/tie-rod/tensioner system according to Figure 11;

- Figure 13 shows a first detail of the system according to Figures 11 and 12; - Figure 14 shows a second detail of the system according to Figures 11 and 12.

With reference to Figures 1 and 2 , 1 denotes a tie-rod for stone materials sawing machinery which is fixed to a blade-holder unit (not shown in the figures) . In particular the figures show a tie-rod 1 called "tensioner side tie-rod" which performs fixing of a cutting blade to the gangsaw as well as tensioning

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of the said blade during the sawing operation.

The tie-rod 1, according to the invention, has a body 2 fixed to the blade-holder unit; the body 2 is partly joined to a head portion 3 which is axially offset ^' with respect to the said body 2. The head portion 3 has a recess or seat 4 which is able to receive the body 2 according to the invention and inside which one end 5 of the body 2 is partially engaged; engagement of the body 2 with the recess or seat 4 is such that the axis of the body 2 coincides with the axis of a blade used for the sawing operation and shown in Figure 3. The part of the end 5 of the tie-rod which is not engaged inside the recess or seat 4 remains free . The body 2 is furthermore fixed to the head portion 3 by means of fixing means such as screws indicated only by way of example by the reference numbers 6 or 8 in Figure 2. Alternatively, or in addition, a second fixed pin 10 projecting from the head portion 3 may be engaged with the body 2 which has a cavity with a corresponding shape. The second fixed pin may have both a circular cross-section and a non- circular cross-section; in a preferred embodiment it has an oval-shaped cross-section. The head portion 3 has a first fixed pin 12 projecting from the same side where it is joined to the body 2, but in its part which it is not engaged with the said body 2.

The first fixed pin 12 acts as lock for a blade 14 shown, together with the tie-rod 1, in Figures 3 and 4 where the same reference numbers as in Figures 1 and 2 are used.

In Figures 3 and 4, the first fixed pin 12 is engaged with a blade 14 provided with a hole (shown in Figure 4) having a shape corresponding to the cross- section of the first fixed pin 12. In a preferred embodiment the first fixed pin 12 has a cross-section which is non-circular, although a circular shape is not excluded.

The blade 14 is mounted by means of its hole 16 onto the first fixed pin 12 so as to be engaged with the tie-rod 1.

Preferably, the assembly consisting of the head portion 3 and the fixed pin 12 forms a single body. Advantageously, according to the invention, the engagement between blade 14 and tie-rod 1 is performed in a manner which is simpler and faster than occurs with the parts designed according to the prior art, which requires locking of a blade in a bracket of the tie-rod and insertion of a movable pin which engages simultaneously with the two flanges of the tie-rod and the blade.

In view of this, replacement of the blades is also faster with a consequent increase in productivity.

Moreover, since the blade 14 and the body 2 of the tie-rod are axially aligned, the force of the tie-rod during displacement of the blade 14 does not occur along a transverse component, but is concentrated in a common blade/tie-rod axial direction. This results in more regular wear of the blade and more precise cutting with a consequent further increase in productivity. In addition, the blade 14 mounted on the first fixed pin 12 may be provided with dimensions so that one of its ends 15 is at a negligible distance from the

end 5 of the body 2 during the sawing operation. This prevents the blade 14 from rotating with respect to the tie-rod 1 during sawing, even where there is only one first fixed pin 12 and it has a circular cross-section. Engagement between the end 5 of the body 2 and the end 15 of the blade 14 therefore provides the entire blade/tie-rod system with a substantial stability during the sawing operation.

Figure 4b shows an example of a tie-rod with blade in which the body 2 of the tie-rod is joined to two head portions 3 of the tie-rod. The body of the tie rod and head portions may have both different heights and the same heights. This second case is shown in the figures; the heights of the body and/or the head portions normally range between 20 and 200 mm.

The first fixed pin may also be in the form of an "L" with the shank of the "L" coinciding with the first fixed pin 12 already described and the arm of the "L" being parallel to the head portion 3 of the tie-rod 1, but separated from it by the length of the shank. The cavity 16 of the blade 14 engages with the fixed L- shaped pin so that the base of the cavity 16 makes contact with the shank of the fixed L-shaped pin and the side wall of the blade 14 remains in contact with the arm of the fixed L-shaped pin. In this way the blade 14 remains secured in a position fixed and parallel to the head portion 3 of the tie-rod and keeps it axis coinciding with the axis of the body 2 of the tie-rod. An alternative to the single first fixed pin 12 consists in a plurality of fixed pins which may have both a circular shape and a non-circular shape,- these pins, in addition to shapes differing each other, may

also have variable dimensions depending on various parameters, including the heightwise dimension of the blade 14, and may be arranged on the head portion 3 of the tie-rod 1 in an aligned or staggered manner. This arrangement therefore allows the blade 14 to be further fastened and secured against rotation with respect to the tie-rod 1 during sawing.

A second embodiment of the tie-rod according to the invention is shown in Figure 6, where components corresponding to those shown in the first embodiment are indicated by numbers increased by 100.

In this figure, a tie-rod 101 has a head portion 103 joined to two parallel bodies 102a, 102b; the head portion 103 has a substantially rectangular shape with a pair of recesses or seats 104 able to receive the bodies 102a, 102b inside which two ends 105 of the latter are partly engaged.

In a symmetrical position with respect to its longitudinal axis, the head portion 103 has two first fixed pins 112.

Two blades 140a, 140b are mounted by means of respective holes on the first fixed pins 112 so as to engage with the head portion 103. The blades 140a, 140b are arranged so that their axes coincide with the respective axes of the bodies 102a, 102b so that the force of the tie-rod 101 during displacement of the blades 140a, 140b is not transmitted along a transverse component, but is concentrated in the axial directions of the blades and the respective bodies of the tie-rod. In this second embodiment the variants relating to the pins already described for the first embodiment are also possible.

Usually, the tie-rods are pre-tensioned, in a known manner, by means of a tool or so-called

"coltellina" (shim) which allows the blade to be placed under a predetermined initial tension via compression of pistons arranged between the blade and the shim.

According to the invention and with particular reference to Figures 7 and 8, the tensioning may be performed by means of piston-type blade tensioner 201 which comprises a plate 120 provided with openings passed through by the bodies 102a, 102b of the tie-rod 101 such as to allow the plate to move with respect to the bodies; the plate makes contact with the pistons, not shown in the figures, on its side directed towards the blades; an advantage of use of the plate 120 is that it may compress in a uniform manner a fairly large number of pistons, unlike the solution according to the prior art. On the opposite side of the plate 120, a third pin 130 passes through the two bodies 102a and 102b of the tie-rod 101. A cam 125 is pivotably mounted on the abovementioned pin and rotatable relative thereto.

During setting up or pre-tensioning of the blades by the operator, the cam 125 is rotated on the pin 130 so as to be pushed against the matching member 126, on the one hand, and against the plate 120, on the other hand. The thrust of the cam 125 on the plate 120 is such that the latter compresses the pistons when the piston-type blade tensioner 201 starts to function and keeps the blades tensioned by the correct amount . The matching member 126 has the function of keeping the bodies 102a and 102b in the respective positions.

The cam 125 may also be used in the solution of

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the first embodiment with the tie-rod 1, replacing the shim according to the prior art and being pivotably mounted on a corresponding through-pin passing inside the body of the tie-rod; the cam rotates as described above; in both solutions more than one cam may also be used, if required.

The solution with the cam may therefore be an alternative to the conventional solution with the shim. In both the embodiments, a further solution which can be used, as an alternative both to the solution with shim according to the prior art and to the solution with cam 125, may consist of a threaded screw 170 which is shown in Figures 9 and 10 with reference, for the sake of simplicity, to the solution with two tie-rods, but may also be used with the single tie-rod solution. Obviously the screw 170 is provided with suitable dimensions for ensuring adequate pressure of the plate on the pistons.

A matching member 126 which has a threaded hole intended to receive by means of screwing the threaded screw 170 is provided; while the threaded shank 171 of the screw protrudes from the matching member 126 and exerts a pressure on the plate 120 in contact with the pistons, the head 172 of the screw projects from the matching member on the opposite side.

Screwing of the threaded screw 170 so as to press against the plate 120 allows the tension of the blade to be maintained. The solution with shim, instead, requires the use of a hammer in order to keep the shim in position so as to ensure correct and constant tensioning of the blade.

A variant of the solution with threaded screw

W

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according to Figures 9 and 10 is shown in Figures 11 to 14 in which parts which are the same as in the preceding figures maintain the same reference number, while the modified parts have a reference number increased by 100. The variant shown in these figures may also be applied both to the solution with a single tie-rod or to a pair of tie-rods.

A matching member 226 which has an L-shaped cross- section, shown in particular in Figures 12 and 13, receives by means of screwing the screw 170. The matching member 226 includes a projection 227 arranged at a height close to that of the top of the bodies 102a and 102b.

A plate 220 with a conventional shape is provided with a recess 228 which engages with the projection 227 so as to form a covering protecting the screw 170, preventing abrasive material falling onto the said screw. In this way rapid deterioration of the thread is avoided, which deterioration would seriously impair the function of being able to screw gradually the screw 170 for tensioning of the blades.