The present invention relates to a protection device for a grinding wheel, particularly but not exclusively for a rotating grinding wheel made of an abrasive materi- al .

The invention can in fact also be applied to other types of grinding wheels, for example also to so-called "CBNs" which have an extremely limited consumption.

Grinding wheels are envisaged in the field of grind- ing, for example of laminator cylinders, paper-mill cylinders, and others, for example rotating grinding wheels made of abrasive material, which act on cylinders or similar pieces being processed.

In these kinds of machine tools, the grinding wheels are rotated inside protections or shelters. The shelters of these grinding wheels must be designed and constructed for containing, under safety conditions, any possible fragment that can be released during the processing, also in the case of breakage or explosion of the grinding wheel during its rotation and of the engagement on the cylinder being processed.

In short, these grinding wheels are currently enclosed in their own shelter, which generally consists of a fixed part (so-called hood) , and a movable part (so- called tile) in addition obviously to a covering and mov- able protection device to have access to the hood for the substitution of the grinding wheel; in particular, these covers can be fixed to the hood by means of hinges and can be opened by rotating them; or by means of guiding devices in which case they can be made to slide manually or with a motor. The tile can be regulated with respect to the hood in order to limit the peripheral portion of non-protected grinding wheel to the maximum, with a variation in the diameter of the grinding wheel itself.

In this respect, reference can be made to the safety regulations UNI EN 13128 and it can be deduced that, for example, shelters for grinding wheels with a diameter D>125 mm must be designed so that, due to peripheral wear, the span between the periphery of the grinding wheel and the movable shelter of the same grinding wheel must be kept at less than or equal to 5 mm.

In view of this requirement, it should also be noted that in current shelters for grinding wheels, the regulation of the distance between the periphery of the grinding wheel and the shelter is generally manual.

When a new grinding wheel is installed, its diameter is normally known and consequently it is generally possible to assign the desired position to the tile without making a direct measurement of the span between tile and periphery of the grinding wheel. During the processing, however, the operator does not know the wear of the grinding wheel moment by moment and in order to satisfy the safety requirement described above, he should verify, after each grinding cycle of the machine, the distance between tile and grinding wheel and consequently intervene to re-establish the safety distance by maneuvering screw controls and/or knobs which allow the tile to be regulated with respect to the grinding wheel .

Furthermore, the cooling fluid necessary for the grinding process causes jets which could, with time, endanger the health of the operator if they regularly reach the latter. It is consequently necessary to minimize the exposed surface of the grinding wheel, also on the side where there is access for substitution, in order to avoid jets and the accidental leakage of the cooling fluid as much as possible.

A general objective of the present invention is to solve the drawbacks cited above of the known art in an extremely simple, economical and particularly functional manner .

A further objective of the present invention is to provide a protection device for a grinding wheel, particularly but not exclusively a rotating grinding wheel made of abrasive material, which can be automatically re- gulated, without the necessity of complex measurements entrusted to the expertise of the operator for maintaining the correct distance between grinding wheel and outer covering element (tile) and, above all, without the di- rect intervention of the operator in a difficult, tiring and dangerous operation.

Another objective of the present invention is to provide a protection device, for example, for a rotating grinding wheel made of abrasive material, which prevents a significant leakage of cooling liquid in the processing phase, in every configuration of the protection device and for each diameter of the grinding wheel.

In view of the above objectives, according to the present invention, a protection device has been con- ceived, particularly but not exclusively for a rotating grinding wheel made of abrasive material, having the characteristics specified in the enclosed claims.

The structural and functional characteristics of the present invention and its advantages with respect to the known art will appear more evident from the following description, referring to the enclosed drawings which, among other things, show an embodiment of a protection device for a rotating grinding wheel made of abrasive material produced according to the same invention.

In the drawings: - figure 1 is a schematic side view of a protection device for a rotating grinding wheel made of abrasive material produced according to the invention in a closed position;

- figure 2 is a schematic view such as that of figure 1 in which some of the parts have been sectioned to allow a better understanding of the invention;

- figure 3 is a schematic view such as that of figure 2 in which some of the parts have been sectioned to allow a better understanding of the invention and which shows the configuration convenient for the insertion of a new grinding wheel;

- figure 4 is a schematic side view of the protection device as shown in figure 3,

- figures 5a, 5b and 5c are a further view such as that of figure 1 from above and an enlarged detail which shows the grinding wheel in contact with the sensor for revealing the actual diameter of the grinding wheel before the facing and grooving cycle;

- figures 6a, 6b and 6c show views similar to those of figures 5a, 5b and 5c when the grinding wheel is in contact with the diamond during the so-called "diamonding" or facing and grooving phase;

figures 7a, 7b and 7c show views similar to those of figures 5a, 5b and 5c which represent the phase in which the correct distance between the fixed part and movable part of the protection device is re-established to ensure the safety requirements described above.

With reference to the figures, these illustrate a protection device for a rotating grinding wheel made of abrasive material produced according to the invention.

The protection device comprises a containment structure comprising a fixed portion 11 with respect to the rotation axis of the grinding wheel assembled on the grinding machine and a movable portion 12.

The movable portion 12 is assembled on a pair of scraping guides 13, having a low friction coefficient, positioned on opposite sides with respect to the grinding wheel .

The fixed portion 11 comprises, constrained to it for example by means of hinges 14, a covering and protection element 15 of the containment structure of a grinding wheel 16.

A motor or driving device, for example a pneumatic cylinder 17, a stem 18 with which, at its free end, it is hinged to the movable portion 12, is constrained to the fixed portion 11 of the containment structure. An electromagnetic blocking unit 19 of the movable part 12 with respect to the fixed part 11 is also envisaged.

A blocking element 20, for example mechanical, acts as a safety device, for the movement of the movable portion 12 with respect to the fixed portion 11. This element can, for example, be a stem-block, which comprises a suitable valve which, when fed with pressurized air, pre- vents the cylinder from effecting movements due, for example, to the residual compressed air inside the cylinder .

The motor 17 is also equipped with a sensor 26 suitable for automatically identifying the position of the movable portion 12 corresponding to a new grinding wheel.

It should be pointed out that, in the embodiment proposed, once the covering element 15 has been overturned to close the grinding wheel 16, it is firmly fixed by means of specific knobs 21 which can be substituted by equivalent means in the case of sliding covering elements .

Furthermore, inside the movable portion close to the area in which the operating opening 22 for the grinding wheel 16 is positioned, there is a nozzle 23 for the emission of cooling and lubricating liquid between the grinding wheel 16 and piece under processing.

Finally, the following devices are assembled on the so-called "piece-holder head" or that part of the grinding machine which rotates the piece being processed: a sensor 25 for revealing the diameter of the grinding wheel before the diamonding, a "diamonding" or facing and grooving unit 29 and, finally, a mechanical buffer 24 on which the movable part 12 rests during the automatic positioning cycle of the movable part 12 with respect to the fixed part 11. These elements 25, 24 and 29 are in front of the movable portion 12 and near the operating opening 22 when the grinding wheel -holder trolley positions the grinding wheel itself in correspondence with the piece-holder head.

The functioning of a protection device for a rotating grinding wheel made of abrasive material produced according to the invention is as follows.

It is first of all necessary to open the covering element 15 by overturning it to be able to position a new grinding wheel 16, as shown in figure 3.

In order to do this, the grinding wheel -holder trolley is brought to a "grinding wheel substitution" position, the advance axis X of the grinding wheel is then withdrawn completely, the electromagnetic brake 19 is unblocked, the cylinder 17 is activated by means of the control unit 27 to move the movable portion 12 away from the fixed portion 11 to allow the grinding wheel 16 to be inserted. In this phase the cylinder goes to the run-end. All the above operations, except for the opening of the covering element 15, can be effected sequentially or au- tomatically, once the specific grinding wheel substitution procedure has been activated on the control unit 27.

Once the grinding wheel 16 has been firmly positioned, the covering element 15 is closed and firmly fixed by means of the knobs 21 or another equivalent blocking device.

At this point, by activating the cylinder 17 in recall mode, the movable portion 12 is brought back onto the fixed portion 11 until the sensor 26 identifies the correct starting operative position on the basis of the maximum value of the diameter of the grinding wheel 16 used.

The cylinder 17 is then stopped and the electromagnetic blockage unit 19 is activated (figure 1) .

The operating cycle initiates with the intervention of the grinding wheel 16 for example on a cylinder to be ground (not shown) .

The diameter of the grinding wheel 16 is controlled by control means of the whole grinding machine consisting of a CNC system, schematized in 27, and when there is a wear of 2-3 mm, a warning/alarm is visualized on a display 28 asking the operator to effect a procedure for reestablishing the safety distance between the movable portion 12 and the fixed portion 11 as soon as possible, i.e. at the end of the grinding cycle underway. The regulation of the movable part 12 with respect to the fixed part 11 can, for example, be effected by means of an automatic cycle managed by the control system 27 after requesting the operator; it is composed of the following phases:

a) The grinding machine positions the grinding wheel-holder trolley so that the grinding wheel is in correspondence with the sensor 25 situated onboard the piece-holder head. The advance axis X of the grinding wheel moves the grinding wheel itself towards the sensor. When the sensor is touched by the grinding wheel, the advance movement stops and the control system 27, on the basis of the position of the advance axis X of the grinding wheel and original diameter of the new grinding wheel, calculates the present diameter.

b) At this point, the grinding wheel -holder trolley is positioned so that the grinding wheel is in correspondence with the facing and grooving unit 29 situated onboard the piece-holder head and the facing and grooving is effected automatically. The control system 27 automatically calculates the decrease in the diameter of the grinding wheel in relation to the increase in the advance axis X of the grinding wheel.

c) Finally, the grinding wheel is positioned so as to put the movable part 12 in correspondence with the reference 24 situated onboard the piece-holder head until it touches it. The brake 19 is unblocked and the advance axis X of the grinding wheel advances until the movable part 12 touches the reference 24. At this point, on the basis of the present diameter of the grinding wheel after the facing and grooving and safety distance established between the movable part 12 and fixed part 11, the control system 27 activates the advance axis X of the grinding wheel which "pushes" the movable part 12 which, as it is not braked and the piston 17 is not charged, moves towards the fixed part 11 positioning the movable part 12 at the desired distance from the grinding wheel. The run of the advance axis X of the grinding wheel necessary for effecting this operation is calculated automatically by the control system 27.

Once the movable part 12 has reached the predetermined position, the magnetic blocking unit 19 is activated.

The operating cycle initiates with the intervention of the grinding wheel 16. It can therefore be understood how the correct position of the protection device is imparted giving the operator more protection in the case of explosion of the grinding wheel and preventing the operator from having any contact with fragments made of abrasive material . Furthermore, the safety of always operating at the correct distance between the grinding wheel 16 and containment structure 11, 12, provides greater control on the emission of the cooling liquid onto the grinding wheel 16 and onto the piece, minimizing the jets outside the machine and damaging the operator's health.

Finally, the possibility of effecting all these operations by means of an automatic cycle, considerably increases the comfort of the operator who is no longer ob- liged, each time the movable part 12 is to be moved towards the fixed part 11, to measure the distance between the grinding wheel 16 and movable part 12 and effect manual operations which, as affirmed in the preamble are inconvenient, difficult and dangerous.

The objective indicated in the preamble of the description has therefore been achieved.

The forms of the structure for producing a protection device for a rotating grinding wheel made of abrasive material of the invention, as also the materials and assembly modes, can obviously differ from those shown for purely illustrative and non-limiting purposes in the drawings .

In particular, as already specified, the invention can be indifferently applied to hoods with both a sliding and rotating cover. The protection scope of the invention is therefore delimited by the enclosed claims.