Technical field

This invention relates to a polishing head.

In particular, this invention relates to a hydraulic polishing head with oscillating toolholders.

These polishing heads are used in particular for polishing machines and/or sanding machines for processing marble, granite, travertine, gres or any other stone material.

Background art

There are currently prior art polishing heads for the sanding and polishing of stone materials comprising, generally, a vertical shaft connected, on one side, to a corresponding motor unit and, on the other side, to a casing, in such a way as to rotate the latter at a predetermined speed.

Between the casing and the element from which the shaft receives the motion there is a fixed reaction flange supported by the casing by means of bearings with axis parallel to that of the shaft.

The casing supports a plurality of toolholder elements to which corresponding abrasive tools can be coupled and which are controlled in an oscillating motion about the respective axes by means of a mechanical transmission connected to the above-mentioned drive shaft, so that each abrasive tool is provided with oscillating motion about the axis of the relative toolholder and, at the same time, rotary motion about the axis of the drive shaft.

With regard to the kinematic connection which allows transmission of the motion from the main shaft to the various toolholders, there are currently various methods.

For example, suitably shaped cams (for example tubular) may be used.

Further, there are embodiments which adopt special connecting rods or levers or rockers provided with rollers which interact with respective cam means.

The use of the above mentioned prior art components may cause non-uniform oscillations of the toolholders due to the very shape of the transmitting means which, when the continuous rotational motion of the drive shaft is transformed into alternating motion of the various driven shafts, may result in dead spots or accelerations.

The occurrence of these phenomena adversely affects the sanding process.

There are also prior art polishing heads which comprise the oscillatory movement of these toolholders by means of motion transmitting means which comprise a plurality of gears (pivoted on corresponding toolholders).

This solution, although it overcomes the drawbacks of the previous type mentioned, can certainly be improved and in turn has several drawbacks.

A first drawback of polishing heads with gear transmission means is due to the fact that such heads do not allow an easy adjustment of the oscillation frequency of the toolholders.

In effect, in order to be able to adjust this frequency the gears must necessarily be changed.

Another drawback is due to the fact that these prior art heads do not always guarantee an optimum response to wear.

Another drawback of these prior art heads is due to the fact that they do not always guarantee an adequate optimisation of the energy consumption.

In effect, a large part of the energy supplied is dissipated by friction.

A further drawback is that these prior art polishing heads are not always simple and inexpensive to make.

Examples of known polishing heads are described in

EP0510603A2 e EP0667210A1.

Aim of the invention

The aim of the invention is therefore to provide a polishing head which is able to overcome the above- mentioned drawbacks of the prior art.

A further aim of the invention is to provide a polishing head which allows the oscillation frequency of the toolholders to be easily varied, in such a way as to be able to easily adapt the performance of the head according to requirements.

Another aim of the invention is to provide a polishing head which is able to provide adequate responses in terms of resistance to wear and optimisation of energy consumption .

A further aim of the invention is to provide a polishing head which is simple and inexpensive to make.

According to the invention, these aims and others are achieved by a polishing head comprising the technical features described in the appended claims. Brief description of the drawings

The technical features of the invention, with reference to the above-mentioned aims, are clearly described in the appended claims and its advantages are apparent from the detailed description which follows, with reference to the accompanying drawings which illustrate purely non-limiting example embodiments of the invention, in which:

- Figure 1 is a perspective side view from above of a polishing head according to the invention;

- Figure 2 is a perspective side view from above of a cross section of the polishing head of Figure 1;

- Figure 3 is a side view from below of a detail of the polishing head of Figure 1;

- Figure 4 is a perspective view from below of a portion of the hydraulic head of Figure 1;

- Figure 5 is a view as in Figure 4 rotated by an angle sufficient for illustrating further components;

- Figure 5b is a scaled-up view of a detail of Figure 5;

Figure 6 illustrates on the Cartesian plane the position of the piston 73 with variations in the time t;

Figure 7 illustrates on the Cartesian plane the position of the piston 74 with variation of the time t.

Detailed description

With reference to Figure 1, the numeral 1 denotes in its entirety a polishing head made in accordance with the invention, hereinafter also referred to simply as the head 1.

The head 1 comprises a first flange 2 for connecting to a drive shaft respective motor means.

The head 1 according to the invention also comprises a box-shaped casing 3.

Advantageously, the casing 3 is connected to the first flange 2 in such a way that the first flange 2 is interposed between the casing 3 and the above-mentioned motor means.

The casing 3 comprises an upper portion 3', a lower portion 3'' and an internal volume V.

Advantageously, the upper portion 3' and the lower portion 3'' are fixed to each other by a plurality of bolts.

Advantageously, the internal volume of the casing 3 is filled with oil.

Moreover, the casing 3 comprises an engaging element 31 operatively connectable to the drive shaft for transmitting a rotary motion to the casing 3, about a relative axis X.

Advantageously, the engaging element 31 is made on the upper portion 3' of the casing 3.

The head 1 according to the invention comprises a plurality of toolholders 4 positioned on the abovementioned lower portion 3" in such a way as to protrude below from the casing 3.

Advantageously, with reference to Figures 1 and 2, the toolholders 4 are positioned on the perimeter of the lower portion 3" of the casing 3.

Advantageously, the toolholders rotate together with the entire casing 3.

Advantageously, the toolholders 4 comprise abrasive tools.

These abrasive tools are designed to engage with stone material for polishing it and sanding it. The abrasive tools can be removed from the respective toolholders 4 so that they can be replaced at the end of their life.

The head 1 also comprises motion transmitting means 5 located in the internal volume V of the casing.

The transmitting means 5 are in an oil bath.

The transmitting means 5 are designed to convert the rotary motion (imparted on the casing 3 by the drive shaft) into an oscillation of the toolholder 4 about the relative axes Y transversal to the axis X.

Advantageously, each of the abrasive tools is designed to engage with stone material for polishing it and sanding it by means of a combined movement of rotation about the axis X and oscillation about the relative axis

Y.

The motion transmitting means 5 comprise a plurality of leverages 6 operatively connected to each of the toolholders 4 and each comprising a first lever 61 and a second lever 62.

The transmitting means 5 also comprise linear actuation hydraulic means 7 comprising first 73 pistons and second

74 pistons.

Advantageously, the hydraulic means 7 comprise pairs of first 71 and second 72 hydraulic cylinders.

Advantageously, the first 73 and second 74 pistons are designed to translate, respectively, inside first 7 and second 72 hydraulic cylinders in a direction parallel to the axis X.

Advantageously, moreover, each pair of first 71 and second 72 hydraulic cylinders is positioned close to each respective leverage 6 along the axis X. The pistons 73 and 74 are movable between a first lowered position and a second raised position, and are in contact, respectively, with the first lever 61 and second lever 62.

In particular, when the pistons 73 or 74 are in the lowered position, they apply a force on the respective first 61 or second 62 lever.

On the other hand, when the pistons 73 or 74 are in the raised position, the respective first 61 or second 62 lever apply a force on the pistons 73 or 74.

The motion transmitting means 5 also comprise a hydraulic circuit 8 designed to supply the linear actuation hydraulic means 7.

This hydraulic circuit 8 is configured for alternately pressurising and discharging the first 73 and the second

74 pistons, in such a way that alternately all the first

73 pistons are in the lowered position and all the second

74 pistons are in the raised position and vice versa.

In particular, as shown in Figures 6 and 7, at each instant t (t1, t2, t3, t4...), each of the first pistons

73 pushes on the respective first lever 61 of each leverage 6 to impart a rotation R to each toolholder 4, and at each instant t+ Δt (t1+ Δt, t2+ Δt, t3+ Δt...) each of the second pistons 74 pushes on the respective second lever 62 of each leverage 6 to impart a rotation R' to each of the toolholders 4.

Advantageously, each repetition of these rotations R and

R' defines an oscillation of the toolholders 4 about the axis Y.

With reference to Figures 6 and 7, at each instant t the pistons 73 are in the lowered position and the pistons 74 are in the raised position, whilst at each instant t+ Δtthe pistons 74 are in the lowered position, and the pistons 73 are in the raised position.

With reference to Figures 3 to 5, the hydraulic circuit

8 comprises a hydraulic pump 81 designed to pick up the oil from the internal volume V of the casing 3 and to introduce it into circulation in the hydraulic circuit

8.

Advantageously, as illustrated in Figure 3, the casing

3 comprises a toothed portion 32 formed internally on the upper portion 3' designed to engage with a toothed wheel 811 of the pump 81, for actuating the pump 81.

Advantageously, the toothed wheel 811 is mounted on the pump 81.

According to further embodiments, the pump 81 is driven by a battery or an electric motor.

Advantageously, the hydraulic circuit 8 comprises a first and a second branch.

The first branch is connected to the first 73 pistons and the second branch is connected to the second 74 pistons.

When the pump 81 is operated, at least one between the first and second branches is under pressure, whilst the other is discharged.

According to another embodiment, not illustrated, the hydraulic circuit 8 comprises a hydraulic pump for each branch, in such a way that the branches can be actuated individually.

The hydraulic circuit 8 also comprises a distributor 82 designed to receive the oil from the pump 81.

The distributor 82 comprises a valve 822 with automatic inversion configured for pressurising alternately the first and second branch.

In particular, the valve 822 with automatic inversion is configured for pressurising a branch until the abrasive tools enter into contact with the stone material to be polished and/or sanded.

When the abrasive tools enter into contact with the stone material, the valve 822 reverses its action pressurising the other branch until the same previous conditions occur.

The first and second branches respectively comprise a first 83' and a second 83'' manifold connected to the distributor 82.

Advantageously, the first 83' and second 83'' manifold comprise an oil flow rate regulator 833.

Advantageously, also, the flow rate regulator 833 is designed to adjust the flow rate of oil inside the hydraulic circuit 8 in such a way as to adjust as required the frequency of oscillation of the abrasive tools.

In particular, the interval Δt between the raised position and the lowered position (and vice versa) for each piston (73, 74) depends on the value of the oil flow rate and may be adjusted by means of the flow rate regulator 833.

The upper portion 3' comprises a second reaction flange

33 designed to dampen any vibrations.

Advantageously, the second reaction flange 33 is interposed between the first flange 2 and the upper portion 3' of the casing 3.

Moreover, advantageously, the second flange 33 is made of elastic material.

The hydraulic circuit 8 comprises a filter 84 for cleaning the circulating oil of any impurities.

The polishing head according to the invention overcomes the above-mentioned drawbacks and brings important advantages.

A first advantage is that the polishing head 1 according to the invention, thanks to its particular operating structure, guarantees a considerable limitation of the risks of wear.

In effect, the simplicity of making the polishing head

1 allows the contacts between mechanical components to be reduced to a minimum, thereby reducing the possibility of wear and damage.

Moreover, reducing to a minimum the contacts between mechanical components considerably reduces the friction and consequently the energy dissipation.

For this reason, the polishing head 1 according to the invention also has the further advantage of providing a product which is able to optimise the energy consumption.

Another advantage of the polishing head 1 according to the invention is due to the possibility of adjusting the oscillation frequency without having to change the structure of the head.