Assembly line, particularly suited for the production of leather and similar goods

The present invention refers to an assembly line particularly suited for the production of leather and similar goods. More in particular, the present invention refers to an assembly line, particularly suited for the production of leather, imitation - leather, hide, fabric, felt, plastics and similar goods, such as foot-wear, slippers, etc. which allows all the production phases to be completed without unloading and re-loading the product.

Many types of assembly line are known for leather, imitation - leather, fabrics, plastic and similar goods, on which moving trolleys equipped with one or more shelves are anchored by fixed,or releasable coupling devices.

The various components of the goods to be produced are placed on the said shelves at the beginning of the cycle, and are progressively assembled in the successive working stations, aligned along the assembly line.

As an example and in order to further help with the understanding of the present invention, specific reference will be made to the production of foot-wear, in which assembly lines are presently widely used.

In the specific case the foot-wear components are placed on the said shelves, such as for example uppers, moulds, inner soles, soles, heels and so on, which are progressively assembled in the successive working stations, aligned along the assembly line.

In correspondence to each of the said stations the operator assigned takes the components that have to be used from the said shelves, mounts them on the portion of the preformed footwear which arrives from the previous station and at the end of the operation, re-loads the footwear obtained onto the same shelves. The trolley that supports the said shelves is then moved to the successive station for another working phase.

Assembly lines of the above mentioned type, and in particular those for foot-wear have made it possible to overcome considerable problems regarding the rationalisation of the working stages and of the working environments, the productivity of the systems, the quality of the finished product and production economicty, however they are not completely satisfactory, since they do not allow all the treatments foreseen by the process to be performed. Hence, for example, the known assembly lines do not permit the treatments to which the footwear is subjected to be performed at the start of the working phases and after the uppers, the toes, the sides and the heels have been mounted . on moulds and before the phases which include the application of the soles, the heels and so on.

The treatments include humidifications, heating by hot air, seasoning with stretching under vacuum and evacuation of vapours and radiation using infra-red ray heaters, at present these treatments are performed outside the assembly line.

To perform these treatments the footwear is unloaded from the assembly line trolleys and placed inside special ovens, or particularly equipped rooms.

At the end of the treatments, the same footwear is removed from the ovens, or taken out of the said rooms and re-placed on the conveyor belt trolleys.

It is obvious that even if the ovens, or the equipped rooms are normally positioned adjacent to the assembly lines, these loading and unloading operations are lengthy and costly.

A multiple containers device may also be used for the stretching and seasoning phases of leather goods and in particular of footwear.

The said containers, which enter and leave the ovens sequentially, transported by a continuous chain make it possible to substantially reduce the hold-up time of the assembly line trolleys in the treatments station.

However the loading and unloading problem of leather and similar goods from the assembly line remains, these having to be performed manually by an assigned operator.

The purpose of the present invention is that of realising an assembly line which makes it possible to overcome the above mentioned drawbacks.

More in particular, the purpose of the present invention is that of realising an assembly line that makes it possible to perform all the process phases to produce leather, imitation-leather, fabricplastic and similar goods without needing to perform any unloading and re-loading operation. Another purpose is that of realising an assembly line which has an extremely simple structure that permits the use of ovens for the treatments foreseen by the process and that is easy and economic to produce.

These and other aims are achieved by an assembly line including : a number of conveyor trolleys travelling on rails and fitted with automatic coupling and release devices; vertical hanging and yoke type support frames, hinged to the conveyor trolleys and ovens to humidify, to heat, to season, to stretch under vacuum, to evacuate the vapours and to radiate using infrared ray heaters, beneath the assembly line straddling the support frames and in sequential series with the working stations.

The ovens are preferably made up of two opposite and sliding doors which when moved close to one another form a seal with the peripheric structure of the vertical support frame. Each support frame may be fitted with cross-pieces sustaining the footwear support brackets, or of other supporting means.

The conveyor trolleys may be fitted with one, or more shelves, or vertical trays.

To better understand the functional and structural character - istics of the assembly line, subject of the present invention, a detailed description will be provided here with reference to the figures of the attached drawings which represent several exemplificative, but non-limitative preferred embodiments and in which: figure 1 is a perspective view of a particular embodiment of footwear trolleys mounted on the rails of an assembly line;

• figure 2 is a side view of the trolley of figure 1, partially sectioned, aligned with an oven to treat the footwear, arranged straddling the hanging frame;
• figure 3 represents the schematic and plan view, of a partial assembly line, subject of the present invention fitted with trolleys with a yoke type frame, on which the product treatment stations are aligned and figures _'4, 5 and 6 represent the schematic views of other types of embodiment of conveyor trolleys fitted with a hanging yoke type frame.

With reference to the figures, the assembly line, subject of the present invention includes a large number of conveyor trolleys 1 and ovens 33 and 34 to perform the humidification , heating, seasoning, stretching treatments, etc. foreseen by the production process.

Each conveyor trolley 1 has a supporting structure 2 to which the front shelves, or supporting trays 3 and 4 of a known type are fixed.

The upper 5 and lower 6 wheels, which run along the rails 7 of the assembly line are applied on the structure 2.

The various drawing, release and coupling devices of the trolleys are not illustrated and described here since they are of a known type and do not concern the present invention. The trays 3 and 4, fixed to the structure 2, may have a single support surface 8, or may be divided into compartments 9 via separators 10.

The upper ends 13 of the up-rights 23 are pivoted to the side edges 12 of the upper tray 3 and to a yoke type support frame 14.

Whereas, pins 16 are fixed in correspondence to the side edges 15 of the lower tray 4 inserted in the transversal slits 17 made on the said ends 13.

Therefore, the frame 14 may rotate about its upper fulcrums 18 and oscillate for an amplitude permitted by the length of the slits 17.

Figures 1 and 2 represent trolleys 1 specifically equipped for the production of footwear 21.

Cross-pieces 19 are fixed in the central part of the frame 14 sustaining the support brackets 20 for the footwear 21. The ovens 33 and 34 for the humidifying, the heating by hot air, the seasoning, the stretching, the evacuation of the vapours and the radiation treatments using infrared ray heaters consist of two sliding half-shells 26 and 27 to enable them to be moved towards and away from one another.

The parallelogram made by the cross-pieces 22 and by the up-rights 23 making up the external structure of the vertical hanging support frame 14, forms a peripheric seal ledge for the doors 24 and 25 of the two half-shells 26 and 27. To achieve the said ledges the above mentioned parallelogram is made using profiles having at least the two side surfaces 28 and 29 in parallel with another and parallel to the surfaces 31 and 32 of the doors 24 and 25.

As can be noted from figure 2, the half-shells 26 and 27, forming the ovens, are mounted beneath the assembly line and straddle the vertical hanging frame 14 so that its external structure, formed by the cross-pieces 22 and by the up-rights 23 are perfectly aligned with the doors 24 and 25.

Again with particular reference to the use of the assembly line, subject of the present invention, for the production of footwear, at the beginning of the working phases the uppers are preferably subjected to an initial humidifying, softening and possible radiation treatment using infra-red ray heaters to revive the toe piece, to facilitate the successive assembly phases on the moulds.

To do this, the uppers and the relative moulds are positioned on the brackets 20 of the hanging frame 14, at the beginning of the working cycle, while the other components of the footwear are pre-arranged in an orderly way on the trays 3 and 4.

A humidification oven is pre-arranged aligned with the successive working station consisting of two half-shells 26 and 27 fitted with doors 24 and 25 which when moved close together form a seal along the parallel side surfaces 28 and 29 of the frame 14. The half-shells 26 and 27 are moved towards one another by means of hydraulic, or pneumatic pistons of a known type ( not illustrated in the figure ) when the structure of the hanging frame 14 is perfectly aligned with the doors 24 and 25, until the surfaces 31 and 32 of the doors come into contact with those 28 and 29 of the frame 14.

During the translation, the half-shells 26 and 27 travel on transversal guides 30 moved by the hydraulic, or pneumatic cylinders.

At this point the oven closes entrapping the hanging frame 14 containing the uppers 21 to be treated.

The oven seal is ensured by means of rubber gaskets 35, or other suitable material, applied to the edges and over the surfaces 31 and 32 of the doors 24 and 25. During the oven treatments of the uppers 21, the other parts of the footwear which must be assembled in the successive working phases, as for example, reinforcements, inner-soles, soles, heels and similar parts, normally remain in the trays 3 and 4 which hence remain outside and above the ovens.

At the end of the treatment the half-shells 26 and 27 retract to their open position freeing the frame 14 from the grip of the doors 24 and 25.

At this point the entire trolley 1 may be transferred to the successive working station.

In the station downstream of the one corresponding to the above mentioned treatment the operator finds all the uppers and the relative moulds 21 still inserted in the brackets 20 of the frame 14 and all the parts to be assembled on the upper trays 3 and 4.

Continuation of the operations occurs in this way without any loss of time.

The trolley 1 advances and passes the successive stations where the parts of the footwear are progressively assembled until complete assembly is achieved in the station up-stream of the one where the ovens for the successive heat treatments are installed.

At the end of the assembly operation of the footwear the operator, instead of loading the footwear into ovens outside the assembly line, or of placing them on one of the trays 3 and 4 for transfer to the successive station, pre-arranges them inside the brackets 20.

The trolleys 1 loaded in this way with the footwear to be treated placed inside the brackets 20 and the remainder of the parts still to be assembled distributed in an orderly way on the trays3 and 4, pass on to the successive station where the ovens 33 and 34 are located.

On reaching this station the frames 14 are once again aligned with the doors 24 and 25 of another oven.

For the sake of clarity a schematic plan view is illustrated in figure 3 detailing a section of the assembly line during this phase.

Two ovens 33 and 34 placed next to one another during the working phase, i.e. closed, are illustrated on the said sections of the assembly line.

Two trolleys 1 are arranged in correspondence to each oven. This arrangement and construction of the ovens makes it possible to half the execution times of the treatment.

The two separate ovens33 and 34 are pre-arranged to perform the humidification and the hot air heating and the seasoning, the stretching under vacuum and radiation using infra-red ray heater treatments respectively. These ovens are not described in detail since they form a part of the technical note.

The automatic introduction of the footwear to be treated inside the said ovens, the seal forming closure of the doors 24 and 25 are entirely similar to those already described for the humidification treatment.

The carding and adhesive spreading phases are performed in the footwear production cycle in succession to the above mentioned treatments.

The rest phase then follows, presently requiring approximately twenty minutes, during which the solvents in the adhesives are completely evacuated, before re-activating the said adhesives and carrying out the application phases of the soles, the heels and of the other possible components. The time required for the 'said rest phase, represents another forced hold-up point of the assembly line process and results in forced speed limits or the engagement of a long section of the assembly line. According to the present invention, this period of time may be significantly decreased by the use of trolleys 1 with a vertical hanging frame 14 and of another opposite half-shell type oven 26 and 27, positioned down-stream of the above mentioned adhesive spreading phase. The footwear 21 with adhesive covered bases and the corresponding soles, also spread with adhesive are placed on the brackets 20 of the support 14 and transferred inside an oven entirely similar to the one described previously.

This oven is equipped with heating means and means of forced suction under vacuum which permit a rapid and total evacuation of the solvents present in the adhesives, significantly reducing the time necessary for this phase. In particular conditions and with the use of several types of adhesives heating of the environment to evacuate the solvents makes it possible to re-activate the adhesive, necessary to make the relative parts adhere to one another in the phase successive to the exit from the oven.

Whereas, in other conditions and however thanks to the structure of the hanging support 14, re-activation of the adhesives is performed outside the above mentioned evacuation oven, but however in sequence on the assembly line without having to unload and re-load the parts spread with adhesive into external ovens, as is the case at present. The heat sources, as for example halogen lamps, necessary to reactivate the adhesives spread over the bottoms, or over the soles, may be conveniently positioned inside the oven close to the surfaces of the soles and/or of the footwear bottoms thanks to the free surrounding space permitted by the structure of the frames 14.

One arrangement example of the heat sources 40 inside an oven to reactivate the adhesives is represented in figure 4.

In the solution illustrated and described, with particular reference to figures 1 and 2, the hanging frame 14 has a fulcrum at the side edges 12 of the upper tray 3 and is pre-arranged to permit its guided oscillation and limited by the pins 16, bound on the side edges 15 of the lower tray 4 and inserted in the slits 17.

It is to be understood that the said solution is preferred in order to guarantee secure matching and a perfect seal between the parallel surfaces 28 and 29 of the hanging frame 14 and those 31 and 32 of the doors 24 and 25 when the half-shells 26 and 27 are moved together.

However, the possibility that the frame 14 may be bound vertically beneath the trays 3 and 4, in another way, independently from them is not excluded.

For example, by means of brackets directly bound to the supporting structure 2, as represented in figure 4. Furthermore, the trolley 1 fitted with a vertical yoke type frame 14, may be equipped with only one, or more than two trays of the type 3 and 4 in its upper part depending on the working requirements, or may be without, as represented in figures 5 and 6.

The structure described and illustrated above has proved to be the most rational and the most economic, in particular for application to footwear assembly lines.

In addition, its structure is such as to permit embodiment, even in pre-existing trolleys.

Other embodiment forms of trolleys with a yoke type frame 14 are represented in figures 4, 5 and 6 applicable to other types of drawing chains, or for other types of use.

In particular, inside the frame 14, instead of the brackets, 20 different over-lying trays 41 may be applied ( see figures 5 and 6).

Another solution may include only the cross-pieces 19 or however other support means which however are contained within the profile of the frame 14.

Another possible embodiment, particularly suitable for the treatment of many pieces, may foresee the frame support 14 with more than one drawing trolley; the fundamental concept remaining that the profile of the hanging frame must always form the ledge for the closing doors of the half-shells 26 and 27 making up the said ovens.

The hanging yoke type frame 14, though being preferably maae up of a peripheric profile having a parallelogram shape to exploit the space enclosed by it in the best and most rational way, may be realised in accordance with any other shape, for example, circular, elliptic, trapezoidal, and so on. In any case, it is essential that its side surfaces 28 and 29 are substantially parallel and have a peripheric profile equal to that of the doors 24 and 25 of the half-shells 26 and 27 of each oven.

While the present invention has been illustrated and described in several of its preferred embodiments it is obvious to experts of the field that various changes to the form and to particulars may be made without be so doing leaving its protective context.