System for detecting and compensating the lateral rotation of a shoe last in respect of the predetermined blocking position in an automatic shoe processing machine

The present description concerns a system to automatically detect and compensate the slight rotations to which a shoe-tree may be subjected during the locking operation which precedes the automatic shoe manufacturing step - for instance, a carding operation on the shoe bottom - in respect of the position taken up by said shoe-tree during the initial learning operation on a sample shoe-tree.

It is well known to the skilled in the art that one of the shoe manufacturing steps involves a carding of the shoe bottom in order to suitably roughen its surface and allow to correctly carry out the subsequent step of sticking the sole. For this purpose, the bottom and the vamp of the shoe are mounted onto a support having the desired shape of the shoe being manufactured and called, in this sector, a "shoe-tree".

To carry out the carding operation, the shoe-trees - on which the shoe bottoms and vamps have been previously mounted - are locked in position between the clamps of a carding machine and are then automatically machined by a carding tool, normally a brush with steel bristles. The carding tool follows a very specific path along the bottom and on the vamp, which path has been previously detected on a sample shoe-tree and memorised in a storage area of the carding machine. The detection on the sample shoe-tree is normally carried out by locking said shoe-tree in the normal working position and by passing, over the area to be carded, an appropriate feeler, the movement of which is detected and memorised by the carding machine, so as to be then exactly reproduced in the movement of the carding tool over the different shoe-trees being inserted, time after time, on the machine. An automatic shoe manufacturing machine of this type is for example disclosed in EP-A-655207.

To make sure that the movement of the carding tool reproduces in a fully identical way the machining path which has been detected on the sample shoe-tree, it is obviously necessary for the single shoe-trees, mounted in succession on the carding machine, to be all locked exactly in the same initial position of the sample shoe-tree. This result is fairly easy to obtain and reproduce in the case of the linear positioning of the shoe-tree in respect of a longitudinal axis of the shoe, as well as of an axis perpendicular thereto and to the shoe sole. It is instead more difficult to reproduce an exact position in the case of the angular setting of the shoe-tree in respect of said longitudinal axis of the shoe. It is in fact possible and it besides.frequently happens that, during the locking operation, the shoe-tree takes up a slightly inclined position on either sides - for example, an inclination varying between a few tenths of a degree and some degrees - in respect of the position originally taken up by the sample shoe-tree when detecting the machining path.

In the manufacture of traditional footwear, the aforedescribed phenomenon has given rise to no appreciable drawbacks. In fact, when the sole is of a substantially flat type, the carding concerns merely the bottom part of the shoe, whereby the slight misalignments in the positioning of the sample shoe-tree - determined by a slight lateral rotation of said shoe-tree - are easily and widely compensated. In fact, the carding tool is normally caused to operate on the shoe with a constant pressure, thanks to the use of elastic or hydraulic means; thus, if the bottom surface of the shoe were to undergo a slight rotation along the longitudinal axis of the shoe, in respect of the ideal working plane - that is, if one side of the bottom surface of the shoe were to be higher than the opposite side - such a difference in height would actually be compensated by a shorter or longer stroke of the carding tool, pressed against the shoe by said elastic or hydraulic means, so that it always works substantially in the same conditions.

The same phenomenon has instead quite different consequences when the machining operation on the shoe - whether it be a carding or sticking operation - must concern also the lateral portion of the vamp, as it typically happens in the case of shoes with a box-type sole. In this type of footwear - which has been having an exceptional development in the last years, particularly in the sector of sports footwear - the outer edge of the sole extends in fact upwards, up to covering the vamp to an extent which may vary between a few millimeters and some centimeters. Moreover, said outer edge may have a uniform configuration, and thus a substantially constant height throughout the perimeter of the sole, or else - as it happens more frequently - it can be variously shaped in the different parts of the sole, so as to give to the shoe special aesthetic features, as well as characteristics of stoutness, foot protection, and so on.

The lateral machining operation on this type of soles is thus particularly delicate. Considering for example the carding operation, it is evident that an insufficient carding does not allow a proper sticking of the sole edge, while an excessive carding prejudices the final quality of the shoe which, in this case, would in fact show a remarkable strip of carded vamp above the edge of the shoe sole.

Taking into account the above, it is thus evident that, when carrying out a machining operation on shoes with a box-type sole, as described heretofore, an angular displacement of the shoe-tree - even only of a few tenths of a degree - in respect of the theoretical position, involves a corresponding positive displacement of the machining limit of the carded area, and precisely a lifting of said limit on one side of the shoe and a lowering thereof on the other side. This would hence simultaneously produce a fault of excessive carding - and thus visible - on one side of the shoe, and a fault of reduced carding - and thus of insufficient sticking of the sole - on the opposite side of the shoe, thereby giving rise to a high depreciation in the quality of the product.

The object of the present invention is to thus supply an automatic shoe manufacturing machine apt to eliminate the above drawback and prevent faulty machining and, in particular, faulty carding operations, i.e. insufficient or excessive carding, caused by a final positioning of the shoe-tree at the end of the locking operation in the carding machine - in relation to the angular setting in respect of the longitudinal axis - differing from that taken up by the sample shoe-tree used for the initial learning of the machining path.

According to the present invention, said object is reached by means of an automatic shoe manufacturing machine and, in particular, in a carding machine, as claimed in claims 1-6 and the method of claim 7.

Other characteristics and advantages of the system according to the present invention will anyhow be more evident from the following detailed description of a preferred embodiment thereof, given with reference to the accompanying drawings, in which:

• Fig. 1 is a diagrammatic plan view of a carding machine including the system according to the present invention;
• Fig. 2 is a side elevation view of the machine of fig. 1, in a rest position; and
• Fig. 3 is a view similar to that of fig. 2, with the carding tool in operation.

The carding machine illustrated on the drawings consists of a guide arm 1, onto which an oscillating arm 2 is hinged in A. On the free end of said arm 2 there is finally fixed a carding tool 3, normally a brush with metal bristles, and the respective driving motor M. The arm 1 is then connected, in known manner, to control and driving means (not shown) which allow to automatically shift the tool 3 according to a desired working path, along a shoe-tree F which is locked in position under the carding tool 3 and on which there are mounted the bottom and the vamp of a shoe being manufactured.

When starting to manufacture a new series of shoes of the same type, a sample shoe-tree is first of all locked in position on the shoe manufacturing machine, and a learning operation is carried out on said sample shoe-tree to learn the machining path which the tool 3 will have to perform over the whole series of shoe-trees F of the same type. However, when said shoe-trees F - mounted in succession - are locked in position in the carding machine, it easily happens - as already mentioned in the introductory part of the present description - that the angular setting of the shoe-tree F in respect of the longitudinal axis Y of the shoe, once said shoe-tree has been locked in position, is rotated by an angle α (fig. 3) in respect of the initial position taken up by the sample shoe-tree during the learning step.

According to the present invention, an encoder 4, coaxial to the hinge A, is set between the arm 1 and the arm 2 and is fixedly connected to one of said arms, so as to be apt to detect the respective angular displacements thereof, then transmitting the data concerning such displacements to the above control means. By processing this new data and comparing them to those previously detected during the learning step on the sample shoe-tree, the system is thus apt to detect the lateral rotation actually undegone by each single shoe-tree F being manufactured, in respect of the position taken up by the sample shoe-tree, and is apt to accordingly modify the machining path of the carding tool 3 in the subsequent working steps, that is, in particular, in the steps which concern the lateral surface of the vamp.

In fact, according to an important characteristic of the present invention, by associating the encoder 4 to the arms 1 and 2 carrying the carding tool 3, it is possible to detect the final angular setting of the shoe-tree F just during the carding operation on the shoe bottom, thereby avoiding to dedicate a specific working step to this detection operation.

It is however evident that if, for any special models of footwear, one should wish to carry out also the bottom carding step according to a "modified" working path, this working step can be preceded by a step exclusively meant to detect the lateral rotation of the shoe-tree, by using a device fully similar to that described heretofore in which the carding tool has been replaced by a common feeler. This last device can also be of the retractable or foldable type and it can be permanently associated to the carding tool, so that it may be possible to use one or the other, according to uses or preferences, with a simple and practical operation.

In the previous description reference has mainly been made to the carding operation on the shoe bottom as a basic shoe manufacturing step, during which it is preferably convenient to detect the lateral rotation of said shoe. This is due, on one hand, to the fact that said operation is normally the first automatic operation carried out on the shoe and, on the other hand, to the fact that - as said above - said operation can normally be carried out correctly also in the presence of a small angular rotation.

The present invention has been described with reference to a particular embodiment thereof, but it is evident that its protection scope is not limited to said embodiment, but extends to any possible variants within reach of a person skilled in the art, provided that they fall within the definitions of the invention given in the accompanying claims.