SURFACES".

Technical field

The present invention relates to a vacuum drying machine for tanned skins, with multiple work surfaces. Background art

Vacuum drying machines are known which comprise a plurality of vertically movable superimposed platforms, each of which defines a work surface with its upper face, the skin or skins to be dried being laid thereon.

Except for the lowest one, each platform is provided, on its lower face, with a cover, the perimetral edge of which can be brought into sealing contact against the underlying work surface; the cover and the underlying platform thus provide, when joined together, an evaporation chamber in which the skins being treated are enclosed.

A cover is furthermore provided above all the platforms, and is also vertically movable or fixed to the framework of the machine, and cooperates with the work surface of the uppermost platform.

To dry the skins, the work surfaces are heated by appropriate heating means and a depression is provided inside the evaporation chambers by suitable aspiration means.

In known drying machines, the platforms and the eventual movable cover are usually moved vertically by pairs of hydraulic single-action cylinders, arranged at the uprights of the framework, provided to the sides of the platforms; each cylinder is provided with its liner fixed to the base of the framework and the upper end of its stem is

fixed to a support which projects from the platform supporting it from below.

Such a system for moving the platforms is however no devoid of disadvantages, among which the main one is that in order to achieve the required operating strokes, ver long cylinders must be used, with accordingly extende liners, which entail large dimensions and are difficult t accommodate inside the machine. It is thus sometime impossible to keep the operating positions of the variou platforms at correct heights, and the overall height of th machine reaches very high values.

Such disadvantages have led to the provision of dryin machines wherein the lowermost platform remains fixed, an the level on which the operator acts to remove the drie skins and lay the skins to be dried varies each time; i.e. the work level varies from a minimum height, which matche that of the fixed height of the work surface of th lowermost platform, progressively increasing as platform .are stacked, up to a maximum increase equal to the thicknes of all the platforms arranged stacked in a pack.

However, in order to perform these changes in level, i is necessary to provide the drying machine with a movabl stand for the operator which shifts to the same height a the work surface one is operating at, thus significantl increasing the complexity of the machine and bein detrimental to the practicality of the work of th personnel .

If, instead, it is intended to provide drying machine wherein the plane on which one operates is always at th same height, it is necessary to provide, moreover, th

motion of the lowermost platform, and longer strokes for the motion of the other platforms. The dimensions and the bulk of the cylinders increase accordingly, and since the fixed work height cannot be lower than the level of the upper end of the liner of the highest cylinder, either the work height is increased excessively, and so is the overall height of the machine, or the cylinders must be made to project below the base of the machine.

However, this last solution is also not devoid of disadvantages, among which the most apparent are the need to provide beforehand a number of recesses on the resting surface, suitable for accommodating the projecting portions of the cylinders, and the practical impossibility of subsequently modifying the position of the machine.

Another disadvantage which sometimes occurs in known drying machines is that the hydraulic cylinders support the platforms from below and thus, being subject to the weight of the platforms, operate in compression. For this reason, when the cylinders are completely extended, the stems project by a great length and are coupled to the liner for a limited length, so that they are often subject to bending and, generally to undesired oscillations.

Another disadvantage of known machines is the particular kind of coupling which must be provided between the upper end of the stem and the supports projecting from the platform, in order to ensure adequate resistance and reliability, even with the small size of the coupling surfaces thus obtainable.

DISCLOSURE OF THE INVENTION

The main aim of the present invention is to eliminate

the disadvantages described above in known types of dryin machines with multiple work surfaces, by devising a drying machine wherein the platforms are moved so that beside allowing to keep constant the height of the work surface on which one operates, with the consequent advantage of th elimination of any movable stand or other equivalent accessory, it is possible to contain both the work heigh and the overall height of the machine, without providing downwardly protruding elements. Within the scope of the above described aim, particular object of the invention is to provide a system o movement wherein the coupling between the platforms and the framework of the machine makes the platforms furthermor subject to a self-centering action which makes them automatically assume the most appropriate position, adaptin to any eventual irregularity in the guiding means, and being able to absorb without any disadvantage thermal variations produced e.g., by the variable heat status of the machine

Another important object is to provide a device fo moving the platforms which is provided with a simplified structure, wherein the component elements can be assembled quickly and without requiring constructive complications and is furthermore designed so as to facilitate transport, installation and any subsequent intervention on the machine, such as e.g. maintenance or replacement of components.

Not least object is to provide the drying machine with a system for moving the platforms which can be easil obtained starting from component elements commonly available on the market and which is furthermore competitive from an economic standpoint.

The aim described above, as well as the objects mentioned and others which will become apparent hereinafter, are achieved by a vacuum drying machine with multiple work surfaces for tanned skins, according to the invention, comprising a fixed framework with at least two substantially vertical uprights extending to the side of a plurality of vertically movable stacked platforms, each of which upwardly defines a work surface, and is provided below with a cover for the underlying platform, characterized in that at least one of said platforms is coupled to the movable liners of at least two linear double-action cylinders, each being located at one of said uprights the upper ends of the stems thereof being connected to the top of the matching upright. BRIEF DESCRIPTION OF THE DRAWINGS Further characteristics and advantages of the invention will become apparent from the description of four preferred, but not exclusive, embodiments, illustrated only by way of non-limitative example in the accompanying drawings, where:

Fig. 1 is a perspective view of a vacuum drying machine wi h multiple work surfaces;

Fig. 2 is a schematic front view of a partially cutou lateral portion of a first embodiment of a drying machine according to the invention, illustrated with the platforms spaced apart; Fig. 3 is a view similar to the one of Fig. 2, which illustrates the opposite lateral portion with the platforms stacked in a pack;

Fig. 4 is a transverse cross section view, performe along the line IV-1V of Fig. 2, illustrating the guiding means and the electric safety device which control th

motion of the platforms;

Fig. 5 is a perspective view of a detail illustratin the coupling of the platforms to the respective liners;

Fig. 6 is a vertical cross section view along the axi of a linear cylinder related to the coupling illustrated i Figure 5;

Fig. 7 is a diagram of a part of the hydraulic syste which controls a pair of cylinders associated to a sam platform; Fig. 8 is a detail of a perspective view illustratin the embodiment of the uprights, which can be disassembled;

Fig. 9 is a schematic lateral view, partly in cros section, of a second embodiment of a drying machin according to the invention, with two platforms and with movable upper cover, illustrated respectively with th platforms and the cover spaced apart and stacked in a pack;

Fig 10 is a schematic, partial cross section view of lateral portion of a third embodiment of a drying machin according to the invention; Fig. 11 is a view, similar to the previous one illustrating a fourth embodiment of a machine according t the invention.

WAYS OF CARRYING OUT THE INVENTION

With reference to the figures, a vacuum drying machin with multiple work surfaces for tanned skins, generall indicated with the reference numeral 1, comprises a framework which is provided laterally with a pair o vertical uprights 3, between which a plurality of platforms 4 extends, which platforms are stacked and arranged i horizontal planes, which are vertically movable, both

independently and in mutual cooperation.

Each platform 4 defines, with its upper face 5, a work surface on which the skin or skins to be dried are laid.

With the exception of the lowermost platform, which is indicated by the reference numeral 4a, the remaining platforms 4 are provided, applied to the lower face, with a cover 6, or with another equivalent element, provided with circumferential borders 7 capable of sealingly coupling to the work platform 5 of the underlying platform, defining a sealed evaporation chamber which operates in depression, wherein the skin or skins, which are being dried, are enclosed.

An upper cover 8, suitable for cooperating with the work surface of the upper platform, indicated with the reference numeral 4b, is provide above all the platforms 4 and can be fixed, as in the example illustrated in Figures 1 to 3, supported by an upper framework 9 which connects the two uprights 3 to each other, or also vertically movable to follow the movements of the underlying platform 4b, as illustrated in Figure 9 related to a two-platform drying machine, indicated with the reference numeral 1a.

Each platform 4 is provided with means for heating the skins laid on the work surface 5 and is associated to a circuit for the condensing of the vapors released by the skins; aspirating means are furthermore provided, such as, e.g., a vacuum pump for each platform 4 or a single pump for all the platforms, which means generate a depression within the evaporation chambers so as to facilitate and accelerate the drying of the skins contained therein. I ⁿ order to provide a preset working cycle during which

each cover, 6 or 8, remains engaged for a preset perio against the underlying work surface 5, moving away therefro when the drying action is complete to allow the extractio of the dried skins and the insertion of new skins to b processed, so that the work surface affected by the ski replacement operation is always positioned at the sam height, all the platforms 4, including the lowermost one 4a and eventually also the upper cover 8 (see Fig. 9), ar vertically movable, operated by a vertical movement device. According to the present invention, said vertica movement device comprises pairs of double-action linea cylinders, such as the double-action hydraulic cylinders 10 which are arranged at the two uprights 3 and are provide with the upper end 11 of their stems 12 suitably coupled b spherical joints 13 to the top 14 of the respective uprigh 3.

The liners 15 of the cylinders 10 thus hang from th respective stem 12 and are vertically movable.

The platforms 4, with the exception of the lowermos platform 4a, have their shorter sides 16 connected to th liners 15 of the various pairs of cylinders 10. It should b noted, in any case that while the upper platform 4b, or th upper cover 8 if movable, couples to the liners 15 proximat to the upper edge thereof, the underlying platforms 4 ar connected to the liners 5 in regions at increasing distance from the matching upper edges; in practice, the distanc from the upper edge of the liners 15 to the coupling regio of the platforms 4 increases for the progressivel underlying platforms by a value equal to the thickness o said platforms, so that when the cylinders 10 are completel

extended, as illustrated in Fig. 3A, all the platforms are consequently stacked in a pack, while, vice versa, when the cylinders 10 are completely retracted, all the platforms are joined to each other and to the upper cover 8. Appropriately, the cylinders 10 are aligned along the longitudinal axis of the platforms 4 and the upper platform 4b is connected to the innermost pair of hydraulic cylinders 10, the underlying planes 4 being progressively coupled to the progressively outer pairs of cylinders 10. More in detail, two parallel arms 17, arranged symmetrically with respect to the longitudinal axis, extend from the shorter sides 16 of the platforms 4, operated by the double-action cylinders 10, and reach the respective cylinder 10 and are coupled, e.g. by means of bolts 18 to the lateral portions 19 of an horizontal plate 20 which is rigidly coupled to the liner 15.

As is better illustrated in Figures 5 and 6, the plates 20 are removably fixed to the liner 15, since each plate 20 is provided with a central hole which, being traversed by the respective liner 15, is provided with a lower lateral region 21 which is larger in diameter and couples with an arrestor abutment rigidly coupled to the liner 15; said arrestor abutment is suitably composed of the circumferential ly protruding crown of a ring 22 which can be split, e.g., into two half-rings, and is accommodated in a atchingly shaped annular groove 23 provided on the outer surface 24 of the liner 15.

The sliding of the plate 20 along the liner 15 is suitably prevented by a drilled plate 25 which, on the opposite side with respect to the plate 20, engages against

the ring 22 and is coupled to the same plate 20 b appropriate securing means, such as screws 26.

As illustrated in Figure 7, which schematicall illustrates a part of the hydraulic circuit preferably used, each pair of double-action cylinders 10, coupled to the sam platform 4 or 4b or to the upper cover 8 if said cover is also vertically movable (see Fig. 9), is operated in synchronized manner by means of a separate volumetric pump 27, e.g. of the piston type and preferably with a variabl flow rate, with full zero setting, mechanically coupled to an electric motor 28.

An hydraulic safety device 29 is suitably inserted on the hydraulic circuit which connects the pump 27 to the respective cylinders 10, and comprises: a reducing valve which reduces the pressure of the hydraulic liquid between the primary circuit, where e.g. approximately 130 bar ma occur, and the secondary circuit, where again approximately the pressure may be around 20 bar; a safety valve; a sequence valve which, hydraulical ly driven by the secondary circuit, activates the primary circuit only when th pressure of the secondary circuit reaches the required value and conversely inhibits the motion of the platforms 4 if th pressure in the secondary is not at the optimum value, e.g. due to tampering or to a malfunction of the reducing valve. An electric valve 30 is furthermore provided on the hydraulic circuit, and controls the automatic operation of the machine, and so is an adjustment valve 31 which, by allowing to modify the flow rate of hydraulic fluid, allows to adjust the speed of descent of the platforms 4. In the circuit of Fig. 7 it is moreover possible to

identify the safety blocks 32, and the aspiration filter 33 and discharge filter 34 arranged at the tank 35 of the hydraulic liquid.

It should be furthermore noted that, during the ascent of a platform 4, the secondary circuit sends in any case into the upper chamber of the related cylinders 10 a low- pressure flow of the hydraulic liquid, so as to always keep said upper chamber filled, even if the platform moves, e.g. in the conditions of depression vacuum, when raised due to the ascent of the underlying platforms 4.

Besides the hydraulic safety device 29 already described, the hydraulic circuit is furthermore provided with an electric safety device, composed of a pressure switch on the secondary circuit, which blocks the motion of the platforms 4 if for any reason the hydraulic driving pressure in said secondary circuit should be lost; the electric safety device thus performs electrically the same function also performed by the safety valv.e.

As already mentioned, the lowermost platform 4a is not operated by the double-action cylinders 10 but is instead suitably supported and shifted, in the embodiments illustrated, by a pair of single-action cylinders 36 which, arranged below it, are provided with fixed liners 37 arranged as a base 38 for the framework 2, from which liners movable stems 39 extend and engage with the lateral regions 40 of the lowermost platform 4a.

The vertical motion of the platforms 4 may be guided by suitable guiding means provided on the framework 2, so that the platforms 4 move vertically and keep exactly parallel to themselves.

In the embodiments illustrated, and as pointed out in Figure 4, said guiding means comprise a pair of transverse shafts 41, mounted freely rotatable on the shorter sides 16 of all the platforms 4 and eventually also of the upper cover 8, if movable; the transverse shafts 41 are provided at each end with a pinion 42 which engages with a complementary front set of teeth 43 of a double vertical rack 44 fixed to the uprights 3.

The guiding means furthermore comprise a pair of longitudinal shafts 45, mounted freely rotatable on the longer sides 46 of all the platforms 4 and eventually of the upper cover 8; the longitudinal shafts 45 are also provided with toothed end wheels 47 which engage in the complementary lateral teeth 48 of the double rack 44. The motion of the platforms 4 is furthermore controlled by a safety device which is preferably composed of bars 49 which, supported in an electrically insulated manner by the related supports 50 extend parallel to the lateral teeth 48 at such a distance as to allow the exact passage of the toothed wheels 47.

When, for any reason, a platform 4 or the movable cover 8 tend to arrange themselves on a non-horizontal plane, one of its toothed wheels 47 touches the bar 49, closing an electric contact which causes the halting of all the movements of the machine.

Mechanical safety devices are furthermore provided on the uprights 3, which devices, as illustrated in Figure 8, are composed of pairs of bolts 51, arranged diagonally on the opposite sides of the two uprights 3, which are capable of supporting the entire weight of all the platforms 4 and

of the eventual movable cover 8; the bolts 51 are operate by actuators 52, e.g. hydraulic or pneumatic, whic alternately cause the reentry of said bolts 51, to allow th passage of the movable elements, and subsequently make th 5 bolts 51 protrude from the uprights 3 until they projec below the platforms 4, to block their descent in case o sudden severe breakdown.

From what has been described, the operation of th supply system of the platforms 4 is evident and can b ° summarized as follows.

The pairs of double-action hydraulic cylinders 10 ar suspended from the top 14 of the uprights 3 and support an move the related platforms 4, 4b and, eventually, the uppe cover 8 connected thereto. 5 In particular, when the hydraulic circuit sends, vi its primary circuit, 'hydraulic liquid into the uppe chambers of the cylinders 10, the liners 15 rise and rais the platform; the weight of the elements supported wil .conversely make the liners 15 descend when the pressure i 0 the primary circuit ceases, thus making the platforms, an the eventual upper movable cover 8, descend at a rate prese by means of the adjustment valve 31.

The platforms 4 can thus move separately and space apart, or keeping one or more covers 6 in contact with th 5 respective work surface 5, so as to keep operative th evaporation chamber provided thereby.

The operation of the system may be controlled eithe manually, or in a semiautomatic or automatic manner, e.g with preset work cycles; validation switches can b 0 furthermore provided which follow the execution of all th

various phases of the work cycles, requiring, to start a n type of work at the end of the preceding one the operatio on the part of the operator, of a suitable control mean such as, e.g., a pedal, a pushbutton or the like. The coupling of the platforms 4 to intermediate regio of the liners 15, with the stems 12 suspended from the t 14 of the uprights 3, allows to provide long strokes f said platforms, since it is possible to bring the wo surfaces 5 to a limited height from the ground, so as to able to arrange the work surface affected by the replacemen or the loading of the skins always at the same level. Th occurs without the need to increase the overall height the machine 1 or to make use of upwardly or downward protruding pistons. The coupling of the stems 12 by means of the spheric joints 13 allows a certain freedom of motion to t platforms 4 which, being subjected to the action exerted their own weight, have self-centering characteristics whi make them arrange spontaneously in the most appropria position, and furthermore allows them to adapt to eventua imperfections of the guiding means and not to be affected differential deformations due to different therma expansions of the various parts of the machine.

Another important advantage featured by the dryin machine described lies in that it is possible to provide t two uprights 3 so that they might be disassembled, by mea of a removable connection 53, by providing, e.g. illustrated in Figure 8, approximately halfway along th height of the uprights 3, two flanges 54 joined by bolts and coupled, at the racks 44, by centering pins 56.

This moreover allows, after the complete assembly an testing of the machine 1 at the manufacturer's works, t have all the platforms 4 descend in a stack, together wit the upper lid 8, after having uncoupled it from th framework 9 making it rest on the uppermost platform 4b, an to disconnect all the upper ends 11 of the stems 12 fro the spherical joints 13 since the entire assembly i supported by the lowermost platform 4a.

The possibility is thus evident of separating the uppe part 57 and the uprights 3 and of transporting more easil the components thus disassembled, which have a much smalle height than the entire machine; during the installation o the machine, it will be easy to proceed with the revers operations to quickly assemble the complex.

Remarkable and evident advantages are thus obtaine with respect to the transport, at the same time solving th problems which arise when the machine 1 is to be move through passages, such as e.g. main doors of tanneries .inner low trusses which are lower than the overall height o the machine 1 when assembled.

It should be furthermore noted that the possibility o moving vertically the lowermost platform 4a facilitates th access to the lower face of the platform 4a itself and t the inner components of the framework 2, thus simplifyin 5 many interventions, such as e.g. replacement or maintenanc in general, which have to be performed on the machine 1.

The coupling of the platforms 4 to the liners 15 though it offers the greatest assurances of reliability an safety, is structurally very simple, easy to assemble an ° disassemble, and does not feature any particula

difficulties in embodiment, as it merely requires th preparation on the liners 15 of the annular grooves 23 which can be easily obtained, e.g., with a turnin operation. Moreover, the system of movement which is the object o the invention uses elements, such as the linear double action cylinders 10 or the spherical joints 13, which ar available on the market, thus avoiding the design and th production of specific particular elements, with consequen benefits from the economical point of view.

The invention thus conceived is susceptible to numerou modifications and variations, all of which are within th scope of the inventive concept.

Thus, as an example, according to a third embodiment illustrated in Fig. 10, the linear double-action cylinder are composed of hydraulic cylinders 58 with a through ste 59. Their stem 59 extends for the entire length of th uprights 3 and is fixed, appropriately by means of pairs o spherical joints 13a, respectively to the top 14 and to th base 60 of the uprights 3.

Also in this third embodiment, the liners 61 of th cylinders 58 are vertically movable and are coupled, similarly to what has been illustrated in Figures 5 and 6 to the smaller sides 16 of the platforms 4. According to a fourth embodiment, illustrated in Figur 11, stemless linear double-action cylinders 62 are instea provided, which comprise a tubular element 63 inside which cylindrical piston is slideable and defines two inner seale chambers and is rigidly connected to a bracket 64 whic projects out of the tubular element 63, through a sealin

device composed of two steel bands or of another suitable apparatus which allows the sealing thereof.

According to the invention, the stemless cylinders 62 are arranged within the uprights 3 fixed both at the top 14 and to the bottom 60, and their bracket 64 is connected to the shorter side 16 of the platforms 4.

Similarly to what has been illustrated in Figure 9, also in these embodiments the upper cover 8 may be eventually vertically movable, so as to be able to follow the movements of the upper platform 4b, it too being operated, e.g., by a matching pair of linear cylinders according to the invention, or by known kinds of moving devices.

The lower platform 4a may also be operated by a pair of double-action linear cylinders, according to the invention, or also, according to a further different embodiment, it may be suspended to cables which, wound on return pulleys placed e.g. at the top 14 of the uprights 3, are connected t ■counterweights. The device which move.s the lowermost platform 4a, i this .last case, will be provided so that the lowermost platform 4a is raised by the counterweights up to the commo work height, while its descent occurs by virtue of the thrust produced by the descent of the overlying platforms. Furthermore, all the details, which may be replaced b other technically equivalent elements, and in practice th materials employed, so long as compatible with the contingent use, as well as the dimensions, may be an according to the requirements and to the state of the art.