-prier art information The dry milling drums are a special category of drums used in leather treating. They are applied to the so-called operations of dry-treating. by which. after the tanning phase, leather is conferred peculiar features. such as softness, brightness. and water-repellence, and the efficience of particular treatments such as colouring is enhanced.

As well known, these drums differ from the drums used in wet treatments substantially by the fact that they are provided with special equipments and devices, such as those for conditioning recirculation air. Moreover, their internal surface is of perfectly smoothed steel. in order to avoid anv damage of the leather and. furthermore. it is possible to control the rotation speed in a more carefulls wav.

As it is for the drums for wet treatment even in these drums it is possible to put gradually special substances and chemicals during specific processings, by means of the central bearing shaft, which is axialls hollow as it is in the drums for wet treatment. In particular. along the shaft's axle, onto one of the drum's bottoms. there is a nozle for spraying substances and chemicals which are put into the drum through the hollow shaft together with the recirculation air.

It has to be noted that, thanks to the progress of sector chemistry, the use of special substances and chemicals tor dry-treating leather is becoming more and more widespread in order to gain considerable benefits on the point of view both qualitative and economic-producii-e of the different treatment processin£s to be done.

SUMMARY OF THE INVENTION One object of the present invention is to protide a drum for drv-treating leather by which a uniform distribution of the chemicals used in the process may be obtained.

Another object is a drum for dry-treating with a high operating flexibilit.

A further aim is a fulling-drum with a greater load capacit than traditional drums, external size being equal.

The above-mentioned objects are achieved by means of a drum for dry- treating leather containing devices for spraying substances and chemicals during different treating processes, said devices being placed onto the inside cylindrical surface of the drum and being controllable during definite angular sectors of the drum's rotation cycle. Different substances and chemicals can be adduced into the sprayings by means of separate adduction pipes.

The sprayings are placed onto the dnim's median cross-section plane and. in a preferred arrangement, they are inside the longitudinal blades which are usually contained in these drums, at a uniform distance onto their internal cylindrical surface.

The substances and chemicals used in a single working process are drawn from one or more drum's external tanks which are connected to the above- mentioned adduction pipes by means of a rotating collector coaxial to the drum's hollow shaft of rotation. said collector being further provided with a series of internal ducts.

The spraying-or injection-devices are controlled by eicctrovalves driven by position sensors detecting the specific intervention angles during the drum's rotation.

This drum can be loaded with a greater quantity of leather than traditional ones. thanks to the sprayings'peripherical placement onto the internal cylindrical surface and to the possibility of injecting substances and chemicals into the drum only during definite angular sectors in the course of the rotation. The limitation of traditional drums is due to the fact that their spray zone is on the central revolving axle of the drum, and therefore the upper level of the leather contained must be lower than the horizontal centre plane, whereas, in the drum of this invention, spraying is possible even in the course of the rotation, when the sprayings are on the upper part of the drum.

It should be noticed that. in this case. each spraying cone is uniformly distributed onto all the upper surface of the leather contained in the drum, whereas this is not possible in traditional drums.

Moreover. a high degree of flexibiliy is obtained thanks to the fact that the spraying or injection devices can be connected both separately to the revolving collector of the chemicals by means of their adduction pipe and to all products, simultaneously, by means of separate adduction pipes : so for example, in the course of a revolving turn, it is possible to inject different substances by different nozzles and, furthermore. it is possible to substitute the products very quickly, for instance between two separate treatments or during one single treatment.

BRIEF DESCRIPTION OF THE 3ROWINGS Further characteristics and advantages of the present invention will be evident in the description of a preferred embodiment of the same. shown in the following with reference to the accompanying drawings, in which : -figure 1 is a frontal view. in partial section, of a milling drum according to the present invention : -figure 2 is a side-Rtie of the drum of fig. l, where portions in partial section are highlighted : -figure 3 is a further side-view of the drum, but referred to a part of the side opposite the fig. 2 one; -figure 4 is a detailed view of a portion of the drum comprising a specific device of the drum ; -figure 5 is a top-view of the portion of fig. 4 -figure 6 is a view, in section, obtained through the section line VI-VI of fig.4; -figure 7 is a view in section of a detailed portion of the drum of figure 1, this section being the result of section planes traced through the drum's central axis.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to figures 1 and 2. 10 indicates a drum for dry-treating leather. or milling drum.

The milling drum (10) comprises a main cylindrical body (11) supporte by the base-plate (12) and rotated b, a motor-reduction unit (13) connected to the drum's external surface (11) onto one of the drum's bottoms (15) by belts (l4X. A fan (23) for recirculating the air inside the drum is next to the motor (13). The outlet of the fan is connected. through a pipe (16). to the hollow shaft (17). shown in fig.7, and through said hollow shaft the air flows inside the drum (11), being diffused by a spreader (18). The air goes out of the drum througli the other part of the hollow shaft, which is onto the drum's opposite circular surface (19); from this point the air is piped, by a tube (20), to an external filter (21) from where it tlows into the fan (23) through another pipe (22). in which the air temperature is checked and properly regulated, according to a known technique, by an usual heat exchanger schematicallv shown in figure 1.

On the lower part of the figure we can see a belt conveyor (24) ; this is generally used in these types of drums for loading and unloading leather throuh a horizontal sliding door (25). Usually, during the phase of loading, one end of the belt conveyor (24) is lifted as much as to reach the door, whereas during the phase of unloading, the conveyor collects the leather coming out from the drum. bv gravity. during the drum's rotation with its door open.

A tank (26) containing substances and chemicals to be injected into the drum (11) during the processing is ex-sternal the base plate (12). A pipe (28) is kept under pressure by a pump (27) integral with the above-mentioned tank (26) ; said pipe (28) is the adduction pipe ot the revolving collector (29). which is provided with a series of eight inlets, as it is shown in figure 1 and, more clearly, in figure 7, Exactly, in this embodiment of the invention, four inlets (30, 31, 32, 33) are used for substances or chemicals. two of them 34. 33) for pneumatic actioning the door's opening and closing. one inlet (36) for nebulizating the substances, and other inlet (37) for controlling the spraying or injection devices described in the following.

It should be noticed that only one inlet (30) is shown in figure 7 and only the axis of the other inlets are represented. sho «-ing their position in longitudinal direction.

As regard the inlets assigne to the chemical products. it has to be specified that in figures 1 and 2, only one (30) of the inlets is connected to a feeding tank (26). whereas, in practice, more than one inlets can be connected to more than one tanks, anf this. for instance, in order to simultaneously use, in the course of only one processing, different substances and products such as water, waxes, silicones or anything else.

Each of the above-mentioned inlets (30, 31, 32, 33) is indeed connected to the spraying or injecting devices (40) peripherally distributed inside the drum (11). Connection is provided by the revolving collector (29), constantly connecting, during the drum's rotation, every single input pipe, analogous to pipe 28, to every single exit pipe (41), according to the fig. 7 scheme. This figure shows that the collector (29) comprises a stator (42), to which several pipes (28) are connected, and a rotor (43) fixed, by screw means (38). with the hollow shaft (17), from which exit pipes (41) branch off. Each one of these pipes is communicating with a rispective duct (44). inserted into the hollow shaft (17), said duct (44) being. in its turn. communicating to a rispective duct (45) inserted into the rotor (43). Each one of these ducts (45) is communicating to a circular cavity (46), traced in the stator (42) in correspondence to each inlet (30-... 37). The circular canities are insulated bv means of rubber rings (47).

The pipes (41) branching off from the hollow shaft (17) are radially placed onto the circular surface (15) of the drum (11), as shown in fig. 2. and. more exactly. in the compartments traced into the drum's sunburst frame (48). these compartments being usually closed by a covering plate (49) shown in fig. 7 but that does not appear in figure 2 for drawing simplicity.

As we can see in figure 2. one of said pipes (4 which corresponds to the 37 inlet conveying the air for controlling the spraying devices (40). is connected, by four electrovalves (50), to four pipes (51) ordering the opening of the valve needles of each spraying or injection device (40).

In fact. in this embodiment, we see that four devices are used for injecting the products into the drum and the, are placed into four of the eight longitudinal blades (52) that these drums are usually equipped with.

Further, we can see that the spraying devices (40) are mostly placed inside the blades (52), at the centre of their length.

Referring to figures 4, 5, and 6, it can be observed that each spraying (40) is connected to three pipes (60, 61. 62), whose use is the following : -pipe 60 adduces air for controlling the injector opening : -pipe 61 adduces air for nebulizating the products or the substances to be injected into the drum : -pipe 62 adduces substances and chemicals.

The last one (62) can be directly connected to one of the pipes (41) associated to the four inlets (30. 31. 32. 33) of the distributor (29). or it can be connected to a collector (63) of said pipes (41), as it is shown in figure 5. In the second case, it is possible to have a mix of products and substances into the pipe (62) by connecting more than one tanks (26) to the rotating distributor (29), collector (63) being provided with unidirectional valves that avoid any flowing of the product from a pipe (41) into the other ones.

The connection scheme of figure 5 is also useful when, for instance during experimental testing, a chemical has to be substituted with another one in a ver brief time : in that case, since there are more than one separate pipes, there is no need to completely discharge the pipe of the previously adduced product, but it is sufficient to disconnect or empty the previously used tank and connect the same filled with the new product, or another one, to a different pipe (28).

As it is shown in figure 6, the injector (40) is fixed inside the blade (52), by means of a square section tubular (53) whose size is the same as the blade's internal width and whose height is the same as the blade's : in said tubular is inserted a profiled bar (54) provided with a vertical shaped slot (5 5) where an appendix (56) integral with the injector body (40) is inserted. The above appendix (56) is provided with a pin (57), for properly fixing the injector (40) to the tubular (53) and. so, to the blade (52) where the tubular is inserted in.

It has to be noted that a plate (58) and a handle (59) are fixed to the tubular (53), for inserting or extracting the whole spraying group from the blade (52). The plate (58) is provided with a central hole through which, by means of a rod (70), it is possible to reach a ring nut (71) regulating the valve needle opening and, consequently, the spraying flow rate. A regulating knob (72), integral with said rod (70), is reachable from the outside after preliminary removal of a closing panel (80).

Figure 4 shows also a further regulating knob (73) used for varying the magnitude of the spraying cone.

Figure 3 shows the proximity sensors (74) used for driving the eicctrovalves(50)that, as already explained, are employed to control the spraying devices (40). These sensors are placed outside the circular surface (19) of the drum (11). at the same angular position of the blades in which the spraying devices to drive are inserted.

An electric rotating connector (75). used to transmit the supply voltage to the electrovalves (50), is shown in the same figure 3.

The operating of the propose milling drum is evident from the above.

However, it is useful to put into evidence that the described structural features confer the drum a high flexibility of use, which is highly innovative if compared with known milling drums.

By using a normal electronic control unit, the driving of electrovalves (50) can be separately or simultaneously varied in order to spray only some specific products at specific phases of the process or a mix of products in other phases of the procedure ; in both cases, however, the spraying phase ot'every spraying device (40) can be timed according to the signals emitted be the correspondent position sensor (74).

Obviously, these sprayings may consist in devices by which substances and chemicals can be nebulized by means of compressed air, as described above. or, more simple. the may consist in traditional nozzles. Moreover, there can be a greater or a lesser number of devices than those above described and, obviously, they can be placed onto different transverse planes of the drum. circular surfaces included. but al ays perimetrically.

It is clear that, as regards the air recirculation, since the drum can be loaded with a quantity of leather exceeding the horizontal median plane a surface with a series of holes, analogous to the diffuser's surface (18). is provided in proximity of the exit hollow shaft.

It's clear also that the spraying or injecting devices (40) can be independent from the blades (52) and be directly connected to the drum's internal cylindrical surface, this being provided with protections in order to avoid any damage ot leather.

These and other modifications may be carried out, always within the limits of the invention as defined in the appended claims.