Sanding machine

A sanding machine (1; 300) comprising a support structure (2; 302) for the piece (3) to be processed and a sanding unit (4) for the piece (3) itself. The sanding unit (4) comprises a frame (40) that supports a winding element (8) cooperating with kinematic means (9) suitable for setting it in motion according to a closed ring configuration on a plane (π1) substantially parallel to the plane (π2) defined by the support structure (2; 302) and a plurality of abrasive elements (10) combined with the winding element (8) spaced from one another and provided with an abrasive surface (16; 416) that comes in contact with the piece (3) during the movement of the winding element (8).

The invention concerns a sanding machine particularly suitable for being used in the surface processing of panels, doors, furniture doors and similar parts.

This type of processing is generally carried out on raw or painted wood-based materials, but in different applications it can be adopted also for different materials, like plastic or metal, to work on corners or to remove the residues of previous processing.

For this purpose automated sanding machines are known, in which appropriate abrasive elements with suitable grain are placed in contact with the surface of the piece to be sanded.

The abrasive elements are generally constituted by abrasive paper strips closed to form a ring and rotating on a pair of pulleys.

A particular type of machines normally used for sanding low relief surfaces involves the use of abrasive brushes comprising a plurality of abrasive tapes, usually interchangeable, applied to the outer surface of a rotating roller.

During operation these brushes are placed in contact with the piece to be sanded, which is set in motion by a conveyor belt on which it is fixed.

The adhesion of the piece to the conveyor belt is guaranteed by the action of suitable pressing elements that press the piece, as well as by the holding effect obtained by means of a suction unit positioned on the surface of the conveyor belt.

The piece to be sanded is set in motion by the conveyor belt substantially in one direction only with respect to the abrasive brushes that, being usually positioned over the conveyor belt, determine the sanding of one side only of the piece to be sanded, usually the visible upper surface.

Obviously, to carry out a complete sanding of all the sides of the piece, including the edges, it is necessary to carry out successive processing steps, including coordinated movements of the abrasive brushes along different axes, or the rotation of the piece so as to position the sides to be sanded in contact with the brushes.

In different applications, to sand the lateral profiles of the piece the machine is provided with a further sanding unit, where the abrasive brushes of the type described above are arranged vertically, so that they can be placed in contact with the side edge of the piece.

A first drawback of these techniques is represented by the fact that the complete sanding of the piece requires several processing cycles.

Another drawback of these techniques is constituted by the fact that the pressure exerted by the abrasive brushes during their rotation may affect the quality of the processing in small pieces, in fact it is difficult for the pressing element to keep the piece adherent to the conveyor belt, due to the dimensions of the brushes themselves.

The aim of this invention is to overcome the drawbacks described above.

One of the main aims of the invention is to manufacture a sanding machine with which a piece can be sanded with a single processing cycle.

Another aim of the invention is to manufacture a sanding machine that is capable of sanding a piece ensuring a higher quality compared to the equivalent machines of the known types.

A further aim of the invention is to manufacture a sanding machine requiring simplified maintenance operations compared to machines of the known types.

The aims described above have been achieved through the implementation of a sanding machine that, according to the contents of the main claim, is of the type comprising a support structure for the piece to be processed and a sanding unit for sanding said piece, characterized in that said sanding unit comprises a frame supporting:at least one winding element cooperating with kinematic means suitable for setting it in motion according to a closed-ring configuration on a plane that is substantially parallel to the plane defined by said support structure;a plurality of abrasive elements combined with said winding element, positioned spaced from one another and provided with at least one abrasive surface suitable for coming in contact with said piece during the movement of said winding element.

According to a favourite application of the invention, the winding element is constituted by a closed belt wound between two pulleys, one of which is motor driven.

Each abrasive element is constituted by a laminar abrasive element connected with the belt by means of a shaft positioned substantially perpendicular to the plane defined by the support structure.

To advantage, along their trajectory the abrasive elements sequentially involve the side edges of the piece and its visible upper surface, thus carrying out the complete sanding of the piece.

The sanding machine object of the invention is shown inFIG. 1, where it is indicated as a whole by1.

It substantially comprises a support structure2for the piece3to be worked and a sanding unit, indicated as a whole by4, for sanding the piece3.

In the application ofFIG. 1the support structure2is movable with respect to the sanding unit4and substantially comprises a conveyor belt5wound to form a closed ring between a pair of rotating cylinders6,7.

In different applications the relative movement between the sanding unit4and the support structure2can be obtained, for example, by moving the sanding unit4only.

According to the invention, the sanding unit4comprises a frame40supporting a winding element8, as can be seen in greater detail inFIG. 2, cooperating with kinematic means, indicated as a whole by9, and a plurality of abrasive elements10, combined with the winding element8and arranged spaced from one another along the development of the winding element8itself.

In particular, the winding element8assumes a closed ring configuration on a plane π1substantially parallel to the plane π2defined by the support structure2.

For convenience's sake said planes π1and π2are positioned horizontally, but it is clear that in different applications they can have any position, even inclined. As to the winding element8, it is constituted by a belt closed to form a ring and cooperating, as already said, with the kinematic means9that set it rotating on plane π1.

The kinematic means9are constituted by two pulleys11,12, between which the winding element8is wound and by motorization means, indicated as a whole by13, mechanically connected with one of said pulleys, in the case represented in the figure with pulley12, to set it rotating.

Each one of the abrasive elements10, as shown inFIG. 7, is constituted by a laminar abrasive element14connected with the winding element8by means of a shaft15arranged substantially perpendicular to the support structure2, where the piece to be processed3is positioned.

The laminar abrasive element14, as shown in the detail ofFIG. 8, is preferably constituted by abrasive strips of the known type, comprising a piece of abrasive paper16, on which a series of fringes is obtained.

The abrasive paper16is positioned at the side of a series of fibrous element17that, owing to their intrinsic elasticity, determine the flexibility of the laminar abrasive element14itself.

As shown in the figures, and in particular in the top views of theFIGS. from 4 to 6, each laminar abrasive element14is positioned inclined with respect to the advance directions of the winding element8, indicated by the arrows18and19, with respect to the two main sides20,21on which the winding element8itself is wound.

This inclination, in fact, ensures the soft aggression of the corners of the piece3with which the laminar abrasive elements come in contact.

The laminar abrasive element14clearly has the abrasive paper16positioned at the front and the fibrous elements17positioned at the rear with respect to the advance directions of the winding element8.

To allow each laminar abrasive element14to be arranged in an inclined position, the shaft15is provided with articulation means, indicated as a whole by22, that make it possible to define, as we shall see later on, suitable and different inclined positions of the laminar abrasive element14.

The articulation means22can be carried out according to known techniques commonly used in the mechanical sector.

To facilitate maintenance operations and the replacement of the laminar abrasive elements14, the same are advantageously joined to their respective support shaft15so that they can be removed, thus ensuring easy and quick replacement.

This is highlighted inFIG. 9, where it can be observed that the laminar abrasive element14is removably constrained to the support shaft15through holding means, indicated as a whole by23, constituted by a movable plate24positioned against the laminar abrasive element14through the operation of a pawl25.

To facilitate the guided movement of the abrasive elements10on the frame40guide means are provided, indicated by26inFIG. 7, substantially constituted by rails that develop at least for part of the length of the winding element8and slidingly receive the shaft15of the abrasive element10.

In particular, the shaft15is combined with rolling sliding means27that, cooperating with the rails26, guide the abrasive elements10, thus reducing the stress on the winding element8and reducing the oscillation of the winding element8to the minimum.

To advantage, said guide means26will develop for a width corresponding to the maximum width admissible for the pieces to be processed.

Combined with the sanding unit4, as it can be observed in detail inFIG. 2, there are pressing elements, indicated as a whole by28, constituted by rollers that during the sanding process are positioned in such a way as to adhere to the piece to be processed3and facilitate its adhesion to the support structure2.

Furthermore, the support structure2may be provided with suction means, not represented in the figure for simplicity's sake and in any case already known, which further increase the adhesion of the piece3.

During operation, as shown inFIGS. 4,5, and6, the piece to be processed3advances in a substantially perpendicular direction with respect to the parallel advance directions18,19of the winding element8.

When at the beginning of the cycle the piece3comes in contact with the abrasive elements10, as shown in detail inFIG. 4, the laminar abrasive elements14of the main side21come in contact with the front side edge3aof the piece3, thus sanding this edge.

Successively the piece3advances further and, as can be observed inFIG. 5, comes in contact with the abrasive elements14of both sides20,21.

In particular, the abrasive elements14of the side20come in contact with the side edge3band the visible upper surface3eof the piece3.

Analogously, the abrasive elements14of the side21come in contact with the side edge3dand the same visible surface3e.

In the last sanding phase, as shown inFIG. 6, the abrasive elements14of the main row20come in contact with the last side edge3cthat hasn't been sanded yet, thus finishing the processing of the piece3.

It is clear that, independently of the shape of the piece to be sanded, all its side edges, as well as its visible surface are sanded in a single processing cycle.

It is also clear that during the processing phases the pressing elements28, not represented in theFIGS. from 4 to 6for simplicity's sake, will be advantageously rested on the upper surface3eof the piece3, in order to keep it adherent to the conveyor belt5.

It is important to point out that, compared to the known types of sanding machines, in this case the pressing elements28can be arranged at a shorter distance from one another, thus ensuring optimal adhesion also for small pieces.

In case of application to more sophisticated sanding machines, a sanding unit4of the type described above may also be advantageously combined with traditional sanding units, for example sanding units with rotary brushes.

TheFIGS. from 10 to 12schematically show a variant of the sanding machine object of the invention during different processing phases; it differs from the previous one for the different inclination of the laminar abrasive elements114.

Said abrasive elements, as it can be observed, are inclined according to an alternate configuration that, compared to the previous application, ensures compensated distribution of stresses on the winding element, due to the contact of the laminar abrasive elements114with the piece to be processed.

In this way the oscillation of the winding element during its rotation can be further reduced and the construction of the sanding machine may be simplified, since there is no need for guide means combined with the shaft of each abrasive element.

FIG. 13shows a further variant of the invention, which differs from the previous applications described above for the different arrangement of the laminar abrasive elements214that, in this case, are perpendicular to the advance directions of the winding element.

FIG. 14shows a further variant of the invention, indicated as a whole by300. It differs from the first practical application for the different construction of the support structure302, which in this case is constituted by a plurality of rotating rollers305positioned side by side which, while rotating, bring with themselves the piece to be processed that rests upon them.

Finally,FIG. 15shows a different construction of the holding means423of the laminar abrasive element414, comprising a movable plate424positioned against the laminar abrasive element414owing to the action of a pair of lateral springs430that are integral with the shaft415.

In this case the laminar abrasive element414can advantageously comprise is two distinct parts416,417, the first part416being constituted by the abrasive paper and the second part417being constituted by fibrous elements.

With this configuration, maintenance operations may require the replacement of the worn abrasive paper416only, with no need to replace also the fibrous elements417.

The above clearly shows that the sanding machine object of the invention, in the different variants illustrated and described herein, achieves the aims set and offers the advantages described.

Upon implementation, further modifications that are not described and represented herein may be made on the machine object of the invention.

Said modifications may be constituted, for example, by a different position of the winding element, by a different execution of the same, for example with ring chains wound on gear wheels, or again by a different execution of the laminar abrasive elements and a different method to apply them to the winding element itself.

These and other variants, not described and not represented herein, must all be considered protected by this patent, provided that they are included in the innovative concepts expressed in the following claims.