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Title:
PNEUMATIC CUTTING DEVICE WITH OSCILLATING BLADE FOR LEATHER CUTTING MACHINES
Document Type and Number:
WIPO Patent Application WO/2020/178729
Kind Code:
A1
Abstract:
The improved pneumatic cutting device (100) comprises an oscillating chamber (1); an oscillating piston (10) having a head (13), predisposed in the oscillating chamber (1), and a rod (14) connected to a cutting blade (L); a pneumatic activating system (P) communicating with the oscillating chamber (1) so as to pneumatically activate the oscillating piston (10) to oscillate in the oscillating chamber (1) and thus cause the cutting blade (L) to oscillate vertically. A first lower cylindrical cavity (162) is present, interiorly of the oscillating chamber (1), and a second upper cylindrical cavity (161), superiorly of the oscillating chamber (1), and the rod (14) comprises a first lower rod part (22), in the first lower cylindrical cavity (162), and a second upper rod part (21), in the second upper cylindrical cavity (161). The pneumatic activating system (P) comprises: a main annular switching chamber (30) and an annular discharge chamber (40), realised in a portion of the walls of the second upper cylindrical cavity (161). The second upper rod part (21) cooperates with the pneumatic activating system (P) for the switching of the oscillation stroke of the oscillating piston (10).

Inventors:
GALLUCCI GIANNI (IT)
Application Number:
IB2020/051789
Publication Date:
September 10, 2020
Filing Date:
March 03, 2020
Export Citation:
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Assignee:
TESEO SPA (IT)
International Classes:
A43D8/02; B23D51/20; B26D1/00; C14B5/00
Domestic Patent References:
WO2018203199A12018-11-08
Attorney, Agent or Firm:
DALL'OLIO, Giancarlo et al. (IT)
Download PDF:
Claims:
CLAIMS

1) An improved pneumatic cutting device (100) having an oscillating blade for leather cutting machines, comprising:

a body (C);

a cutting blade (L) for cutting a leather sheet (V) stretched on a work plane; an oscillating chamber (1), internal of the body (C), comprising an upper end- run wall (11) and a lower end-run wall (12);

an oscillating piston (10), having a head (13) and a rod (14), the oscillating piston (10) being predisposed with the head (13) thereof inserted in the oscillating chamber (1), between the upper end-run wall (11) and the lower end-run wall (12), the rod (14) being connected to the cutting blade (L);

a pneumatic activating system (P) comprising a pneumatic supply source (P1), configured so that a part (1A) of the oscillating chamber (1) comprised between the head (13) of the oscillating piston (10) and the lower end-run wall (12), and a part (1 B) of the oscillating chamber (1) comprised between the head (13) of the oscillating piston (10) and the upper end-run wall (11), are placed in communication alternatingly with the pneumatic supply source (P1) so as to pneumatically activate the head (13) of the oscillating piston (10) to oscillate inside the oscillating chamber (1) between the lower end-run wall (12) and the upper end-run wall (11), and therefore cause the rod (14) and consequently the cutting blade (L) to oscillate vertically between a lower cutting position (L1) of the leather sheet, when the head (13) of the oscillating piston (10) is in abutment against the lower end-run wall (12), and an upper cutting position (L2) of the leather sheet, when the head (13) of the oscillating piston (10) is in abutment against the upper end-run wall (11);

the upper end-run wall (11) being predisposed in the body (C) with respect to the lower end-run wall (12) in such a way that when the cutting blade (L) reaches the upper cutting position (L2) during the vertical oscillation thereof, it remains substantially in contact with, or slightly extracted from, the leather sheet (V) to be cut;

characterised in that:

the body (C) comprises a first lower cylindrical cavity (162), interiorly of the oscillating chamber (1), and a second upper cylindrical cavity (161), superiorly of the oscillating chamber (1);

the rod (14) is realised in such a way as to comprise a first lower rod part (22), comprised between the head (13) of the oscillating piston (10) and the cutting blade (L), arranged in such a way as to be able to slide in the first lower cylindrical cavity (162), and a second upper rod part (21), above the head (13) and arranged in such a way as to be able to slide in the second upper cylindrical cavity (161); the pneumatic activating system (P) comprises:

a main annular switching chamber (30), realised in a portion of the walls of the second upper cylindrical cavity (161);

a main conduit (31) realised in the body (C) so as to place the pneumatic supply source (P1) in communication with the main annular switching chamber (30);

a discharge (SO) comprising an annular discharge chamber (40), realised in a portion of the walls of the second upper cylindrical cavity (161) superiorly of the main annular switching chamber (30), and a discharge conduit (41) realised in the body (C) so as place the annular discharge chamber (40) in communication with the outside of the body (C);

a secondary annular switching chamber (35), realised at the lower end-run wall (12) of the oscillating chamber (10), and in communication with the part (1A) of the oscillating chamber (1) comprised between the head (13) and the lower end-run wall (12);

an annular air passage hole (38), realised at the upper end-run wall (11) so as to place in communication the part (1 B) of the oscillating chamber (1) comprised between the head (13) and the upper end-run wall (11) in communication with the second upper cylindrical cavity (161); wherein the second upper rod part (21) is conformed so as to comprise two annular projections (211 , 212), an upper annular projection (211) and a lower annular projection (212), and an annular recess (201) between the upper annular projection (211) and the lower annular projection (212), the upper annular projection (211) and the lower annular projection (212) being in sliding contact with the walls of the second upper cylindrical cavity (161);

and with the rod (14) further comprising:

a first internal conduit (24), internally of the second upper rod part (21) and having an initial upper part between the upper annular projection (211) and the lower annular projection (212), and a length that is such as to cross the head (13) of the oscillating piston (10) and to have a final lower part in an upper portion of the first lower rod part (22) below the head (13);

a first through-hole (25), realised between the upper annular projection (211) and the lower annular projection (212) of the second upper rod part (21), in order to place the first internal conduit (24) in communication with the outside of the second upper rod part (21);

a second through-hole (26), realised in the final lower part of the first internal conduit (24) below the head (13) of the oscillating piston (10), so as to place the first internal conduit (24) in communication with the outside of the first lower rod part (22);

a second internal conduit (27), realised in the second upper rod part (21); a third through-hole (28) realised inferiorly of the lower annular projection (212) of the second upper rod part (21), in order to place the second internal conduit (27) in communication with the outside of the second upper rod part (21);

a fourth through-hole (29) realised superiorly of the upper annular projection (211) of the second upper rod part (21), in order to place the second internal conduit (27) in communication with the outside of the second upper rod part (21);

the main annular switching chamber (30) and the annular discharge chamber (40) being mutually arranged, the annular recess (201) of the second upper rod part (21) having dimensions such that, the first through-hole (25) being positioned with respect to the annular recess (201) and the third through-hole (28) being positioned with respect to the lower annular projection (212) and the second through-hole (26) being positioned with respect to the head (13), so that, with the alternating sliding of the second upper rod part (21) in the second upper cylindrical cavity (161):

when the annular recess (201) of the second upper rod part (21) is positioned at the main annular switching chamber (30), the upper annular projection (211) is interposed between the main annular switching chamber (30) and the annular discharge chamber (40), the first through-hole (25) is in communication with the main annular switching chamber (30), the second through-hole (26) is in communication with the secondary annular switching chamber (35) and the fourth through-hole (29) is in communication with the annular discharge chamber (40), so that the main conduit (31) is in communication, via the main annular switching chamber (30), the first through- hole (25), the first internal conduit (24) and the second through-hole (26), with the secondary annular switching chamber (35), and therefore the pneumatic supply source (P1) is in communication with the part (1A) of the oscillating chamber (1) comprised between the head (13) of the oscillating piston (10) and the lower end-run wall (12), while the part (1 B) of the oscillating chamber (1), comprised between the head (13) of the oscillating piston (10) and the upper end-run wall (11), is in communication with the annular discharge chamber (40), and therefore with outside, through the annular air passage hole (38), the third through-hole (28), the second internal conduit (26) and the fourth through-hole (29), so that the oscillating piston (10) can be pneumatically pushed upwards;

and when the annular recess (201) of the second upper rod part (21) is positioned at the first annular discharge chamber (40), the lower annular projection (212) is interposed between the annular discharge chamber (40) and the main annular switching chamber (30), the main annular switching chamber (30) is in communication with the annular air passage hole (38), the first through-hole (25) is in communication with the annular discharge chamber (40), so that the main conduit (31) is in communication, via the main annular switching chamber (30), with the annular air passage hole (38), and therefore the pneumatic supply source (P1) is in communication with the part (1 B) of the oscillating chamber (1) comprised between the head (13) of the oscillating piston (10) and the upper end-run wall (11), while the part (1A) of the oscillating chamber (1), comprised between the head (13) of the oscillating piston (10) and the lower end-run wall (12), is in communication with the annular discharge chamber (40), and therefore with outside, through the second through-hole (26), the first internal conduit (24) and the first through- hole (25), so that the oscillating piston (10) can be pneumatically pushed downwards.

2) The improved pneumatic cutting device (100) of claim 1 , wherein the second upper cylindrical cavity (161) has a greater height than the height of the second upper rod part (21), so that, during the alternating sliding of the second upper rod part (21) in the second upper cylindrical cavity (161), when the head (13) of the oscillating piston (10) is in abutment against the upper end-run wall (11), the upper end of the second upper rod part (21) remains distant from the upper end of the second upper cylindrical cavity (161) so as to define between them a thrust chamber (33), and wherein the fourth through- hole (29) is realised in a portion of the second upper rod part (21) above the upper annular projection (211) so that, when the annular recess (201) of the second upper rod part (21) is positioned at the annular discharge chamber (40), the lower annular projection (212) being interposed between the annular discharge chamber (40) and the main annular switching chamber (30) and the third through-hole (28) at the main annular switching chamber (30), the upper annular projection (211) is located above the annular discharge chamber (40) and the fourth through-hole (29) is located at the thrust chamber (33), so that the thrust chamber (33) is in communication, through the fourth through-hole (29), the second internal conduit (27) and the third through-hole (28) and the main annular switching chamber (30), with the pneumatic supply source (P1) so that a part of pneumatic supply can be directed into the thrust chamber (33) in order to provide a further downward pneumatic thrust of the oscillating piston (10).

3) The improved pneumatic cutting device (100) of any one of the preceding claims, wherein the lower rod part (22) has a smaller diameter than the diameter of the upper rod part (21).

4) The improved pneumatic cutting device (100) of any one of the preceding claims, wherein the portion of the upper rod part (21) between the lower annular projection (212) and the head (13) of the oscillating piston (10) has a smaller diameter than the diameter of the second upper cylindrical cavity (161) so as to identify between them an annular air passage channel (39) in order to facilitate the passage of the flow of pneumatic supply from the main annular switching chamber (30) to the annular air passage hole (38) when, with the sliding of the second upper rod part (21) in the second upper cylindrical cavity (161), the annular recess (201) of the second upper rod part (21) is positioned at the annular discharge chamber (40), the lower annular projection (212) being interposed between the annular discharge chamber (40) and the main annular switching chamber (30), and the head (13) of the oscillating piston (10) is in abutment against the upper end-run wall (11).

Description:
PNEUMATIC CUTTING DEVICE WITH OSCILLATING BLADE FOR LEATHER CUTTING MACHINES

FIELD OF THE INVENTION

The present invention relates to the technical sector concerning cutting machines for cutting sheet materials, such as skins, leather sheets, hides, synthetic leather, etc.

In particular, the present invention relates to a cutting device having an improved pneumatically-powered oscillating blade destined to be mounted on the cutting machines.

DESCRIPTION OF THE PRIOR ART

As is known, cutting machines comprise: a work plane, where the materials to be cut are laid out, such as for example leather sheets, synthetic skins and the like; a frame, mounted above the work plane; and a cutting device mounted on the frame and inferiorly provided with a cutting blade.

Movement means are also comprised, which are borne by the frame and mobile with respect thereto, so as to move the cutting device according to the three Cartesian axes above the work plane.

In this way, the cutting blade can be positioned above the leather sheets, be lowered to score the skin and be moved according to a given cutting pathway so as to cut the skins on the basis of prefixed and/or desired profiles.

The cutting devices used for this purpose are predisposed so that the cutting blade can be made to oscillate vertically during the cutting of the leather sheets, from a lower cutting position to an upper cutting position, while always remaining within the thickness of the material to be scored/cut.

For this purpose, at present pneumatically-powered cutting devices are particularly used to cause the cutting blade to perform the requested oscillation needed to carry out the cut.

Pneumatically-powered cutting devices are known, made in such a way as to comprise: an oscillating chamber, having an upper end-run wall and a lower end-run wall; an oscillating piston, comprising a head, arranged in the oscillating chamber, and a rod which is connected on one side to the head, and on the other to the cutting blade; and a pneumatic activating system communicating with the oscillating chamber in order to cause the piston head to oscillate in the oscillating chamber, between the upper end-run wall and the lower end-run wall, and therefore the rod to cause the cutting blade to oscillate vertically.

In these known cutting devices, the pneumatic activating system is configured in such a way that the part of the oscillating chamber comprised between the piston head and the upper end-run wall, and the part of the oscillating chamber comprised between the piston head and the lower end-run wall, are made alternatingly communicating with a pneumatic supply and with at least a discharge so as to make the oscillation of the piston head possible inside the oscillating chamber.

In this regard, in these known cutting devices, the oscillating chamber comprises two openings and the pneumatic activating system comprises conduits, which substantially have a same transversal section and which are respectively in communication with the openings and with the respective external shutters or other external valve organs activatable to open or close so as to make each of the two openings of the oscillating chamber, via the conduits, alternatingly in communication with the pneumatic supply and the discharge.

In this type of known pneumatic cutting devices, the switching of the oscillation of the piston takes place by means of use of appropriate external valve organs or external shutters.

This means that the switching of the piston stroke can take place with a certain delay with respect to the opening/closing of the switching member, a circumstance that can cause the entity of the oscillation stroke of the piston to be not always constant, i.e. sometimes shorter and sometimes longer than the desired run.

This circumstance can have a negative effect on the effectiveness of the cut. The Applicant has obviated the above-described drawbacks by providing a special pneumatic cutting device with an oscillating blade, as described in International Patent Application WO2018/203199.

The pneumatic cutting device (90) described in the above patent application comprises a body (C) and a cutting blade (L) for cutting a leather sheet stretched on a work plane.

The pneumatic cutting device (90) in this regard is mountable on cutting machines, for example numerically controlled.

The device is predisposed in such a way as to pneumatically activate the cutting blade (L) in order that it can oscillate vertically so as to score and cut the leather sheet.

Figures from 1A to 1C illustrate, in frontal views, the pneumatic cutting device (90), with the cutting blade (L) represented in different operating configurations attainable during oscillation thereof, respectively a lower cutting position (L1) (see figure 1A), an intermediate cutting position (LM) (see figure 1 B) and an upper cutting position (L2) (see figure 1C).

The cutting device (90) is provided, internally of the body (C), with an oscillating chamber (1), with an upper end-run wall (11) and a lower end-run wall (12), and an oscillating piston (10), having a head (13) and a rod (14).

The oscillating piston (10) is predisposed with the head (13) thereof inserted in the oscillating chamber (1), between the upper end-run wall (11) and the lower end-run wall (12), the rod (14) being connected to the cutting blade (L).

When the head (13) of the oscillating piston (10) is in abutment against the lower end-run wall (12) of the oscillating chamber (1), the cutting blade (L) is in the lower cutting position (L1), while when the head (13) of the oscillating piston (10) is in abutment against the upper end-run wall (11) of the oscillating chamber (1), the cutting blade (L) is in the upper cutting position (L2).

The upper end-run wall (11) is predisposed in the body (C) at a distance with respect to the lower end-run wall (12) so that, when the head (13) of the oscillating piston (10) is in abutment against the upper end-run wall (11), the cutting blade (L) reaches an upper cutting position (L2) such that it remains constantly in contact with the leather sheet to be cut, or slightly extracted with the aim of guaranteeing continuity to the cutting operation.

The distance between the upper end-run wall (11) and the lower end-run wall (12) thus determines the entity of the oscillation stroke that the cutting blade (L) can make.

For the pneumatic activating of the oscillation of the head (13) of the oscillating piston (10) in the relative oscillating chamber (1), and thus for the vertical oscillation of the cutting blade (L), the pneumatic cutting device (90) is provided with a relative pneumatic activating system (P) communicating with the oscillating chamber (1).

The pneumatic cutting device (90) realised according to what is described in this patent application belonging to the Applicant is able to carry out the switching of the run of the oscillating piston (10) automatically, i.e. without the presence of external valve organs and/or switching organs, this is due to the following characteristics: the particular conformation of the rod (14) of the piston (10), the special conformation of the head (13) of the piston (10) and the special conformation of the pneumatic supply system (P).

These particular characteristics are illustrated in detail in figures from 2A to 2C which represent the views along section lines l-l, ll-ll and Ill-Ill of figures 1A, 1 B, 1C.

The pneumatic activating system (P) comprises a pneumatic supply source (for example compressed air), denoted schematically by arrow (P1), an upper discharge (S1) and a lower discharge (S2).

The body (C) is made in such a way as to comprise a cylindrical cavity (16) and the rod (14) of the oscillating piston (10) is predisposed so as to be slidable alternatingly in the cylindrical cavity (16).

Further, the rod (14) of the oscillating piston (10) is conformed in such a way as to have, in a relative sliding part in the cylindrical cavity (16) below the oscillating chamber (1), and thus in a lower position than the head (13): two annular portions (141 , 142): an upper annular portion (141) and a lower annular portion (142), which are in sliding contact with the walls of the cylindrical cavity (16);

an annular recess (140), comprised between the two annular portions (141 , 142);

and an internal conduit (17).

The rod (14) is further provided with through-holes (18) which are predisposed along the rod (14) in a position below the lower annular portion (142) and such as to place the internal conduit (17) in contact with the outside of the rod (14).

The head (13) of the oscillating piston (10) is provided in turn with at least a hole (130) predisposed so as to place the internal conduit (17) of the rod (14) in communication with the part (1 B) of the oscillating chamber (1) comprised between the head (13) of the oscillating piston (10) and the upper end-run wall (11) of the oscillating chamber (1).

The pneumatic activating system (P) is predisposed and configured in the following way.

It comprises:

a switching chamber (8) of the oscillation of the oscillating piston (10) which comprises an upper annular chamber (8A) and a lower annular chamber (8B) realised in a portion of the walls of the cylindrical cavity (16) in a position below the oscillating chamber (1) at the oscillation zone of the two annular portions (141 , 142) of the rod (14);

a main conduit (81) which is realised and predisposed in the body (C) so as to be in communication, on one side, with the pneumatic supply source (P1) and, on the other side, with a part of the lower annular chamber (8B) of the switching chamber (8);

a secondary conduit (82) realised and predisposed in the body (C) so as to place the upper annular chamber (8A) of the switching chamber (8) in communication with the oscillating chamber (1) via a passage hole (83) realised in the lower end-run wall (12) of the oscillating chamber (1). The upper discharge (S1) is made in a portion of the walls of the cylindrical cavity (16) above the upper annular chamber (8A) of the switching chamber (8), and communicating with the outside via a first discharge conduit (92) also realised and predisposed in the body (C).

In turn, the lower discharge (S2) is made in a portion of the walls of the cylindrical cavity (16) below the lower annular chamber (8B) of the switching chamber (8), and communicates with the outside via a second discharge conduit (94) realised and predisposed in the body (C).

Further, the annular recess (140) of the rod (14) has dimensions so that, and the holes (18) of the rod (14) are positioned below the lower annular portion (142) and with respect to the annular recess (140) in such a way that, with the alternating sliding of the rod (14) in the cylindrical cavity (16) the following conditions occur:

when the annular recess (140) of the rod (14) is positioned at the switching chamber (8) so as to place the lower annular chamber (8B) and the upper annular chamber (8A) in communication, the holes (18) of the rod (14) are positioned at the lower discharge (S2) (see figure 2A), so that the main conduit (81) is in communication, via the lower annular chamber (8B), the annular recess (140) and the upper annular chamber (8A), with the secondary conduit (82) and therefore the pneumatic supply source (P1) is in communication with the part (1A) of the oscillating chamber (1) comprised between the head (13) of the oscillating piston (10) and the lower end-run wall (12) (see the arrows with the continuous line, again in figure 2A), while the part (1 B) of the oscillating chamber (1), comprised between the head (13) of the oscillating piston (10) and the upper end-run wall (11), is in communication with the lower discharge (S2), and then via the second discharge conduit (94) with the outside, through the hole (130) of the head (13) of the piston (10), the internal conduit (17) of the rod (14) and the holes (18) of the rod (14) (see the arrows with the broken line in figure 2A), so that the oscillating piston (10) can be pneumatically pushed upwards;

and when the annular recess (140) of the second upper rod part (14) is positioned at both the upper discharge (S1) and in the upper annular chamber (8A) of the switching chamber (8) communicating with the secondary conduit (82), the holes (18) of the rod (14) are at the lower annular chamber (8B) of the switching chamber (8) and are therefore in communication with the main conduit (81) (see figure 2C), so that the pneumatic supply source (P1), via the main conduit (81), the holes (18) of the rod (14), the internal conduit (17) of the rod (14) and the hole (130) present in the head (13) of the oscillating piston (10) is in communication with the part (1 B) of the oscillating chamber (1), comprised between the upper end-run wall (11) and the head (13) of the oscillating piston (10) (see the arrows with the continuous line, again in figure 2C), while the part (1A) of the oscillating chamber (1), comprised between the head (13) of the oscillating piston (10) and the lower end-run wall (12), is in communication with the upper discharge (S1) via the secondary conduit (82), the upper annular chamber (8A) of the switching chamber (8) and the annular recess (140), and then via the first discharge conduit (92) with the outside (see the arrows with the broken line in figure 2C), so that the oscillating piston (10) can be pneumatically pushed downwards.

Figure 2B illustrates instead the situation in an intermediate position of the rod (14) of the oscillating piston (10) with respect to the end positions illustrated in figures 2A and 2C, con figure 2A illustrating the head (13) of the oscillating piston (10) in abutment against the lower end-run wall (12), while figure 2C illustrates the head (13) of the oscillating piston (10) in abutment against the upper end-run wall (11).

Owing to the special characteristics as set out in the foregoing, in the pneumatic cutting device (90) described in the above-mentioned patent application belonging to the Applicant, the switching of the oscillation of the piston is activated and determined by the piston, according to the position of the relative rod with respect to the cylindrical cavity of the body, and in particular of the relative annular recess with respect to the switching chamber and the two discharges.

This has enabled obviating the drawbacks mentioned in the foregoing in pneumatic cutting devices which include the use of external valve organs or external shutters for commanding the switching of the oscillation of the piston.

The pneumatic cutting device has been found to be very effective for carrying out the cutting of materials in sheet form having a quite slim thickness, with the oscillation stroke of the piston therefore being substantially short, about 1.3 - 1.5 mm.

In the case of cutting operations to be carried out on sheet materials having greater thickness, the pneumatic cutting device will have to be designed and realised in such a way as to enable the piston, i.e. the head oscillating internally of the oscillating chamber, to carry out longer stroke runs.

Consequently, as well as increasing the distance between the lower end-run wall and the upper end-run wall, it is also necessary to increase the length of the rod, the length of the main conduit and of the auxiliary conduit of the pneumatic supply system, as well as repositioning the upper annular chamber and the lower annular chamber of the switching chamber in the device body.

Further, in the case of cutting operations to be carried out on hard sheet materials, such as leather, or very thick, such as cardboard for example, the part of the rod that is beneath the oscillating chamber, and on which the annular recess and the two annular portions are realised, is the one that will be subject to the greatest stresses, and thus the one subjected to the greatest transversal flexions.

The onset of transversal flexions on the part of the rod that comprises the annular recess and the two annular portions can lead to the risk of snagging of the annular portions during the passage thereof at the upper annular chamber and the lower annular chamber of the switching chamber.

Attempts to obviate these issues have been carried out, by increasing the relative length of the rod and also the diameter, or thickness, beyond the length of the rod, so as to stiffen the part of the rod in which the two annular portions and the annular recess are realised, which are responsible for the switching of the oscillation of the piston when they pass at the lower annular chamber and the upper annular chamber of the switching chamber. However, this has led to an increase in the overall mass of the piston and thus a reduction of the accelerations which can be reached, since the air injected into the switching chamber has to accelerate a greater mass, with a consequent reduction in cutting productivity.

Further, in order to seek to obtain acceptable accelerations in cases of increase in the thickness of the rod, and thus a greater mass of the piston which is to be set in oscillation, an attempt was made to increase the quantity of injectable air using the pneumatic supply system, by increasing the volume of the upper annular chamber and the lower annular chamber of the switching chamber.

This, however, led to constructional issues concerning the realisation of the device body as well as the cylindrical cavity.

SUMMARY OF THE INVENTION

An aim of the present invention is therefore to disclose a new improved pneumatic cutting device having an oscillating blade for leather cutting machines able to obviate the above-specified drawbacks.

In particular, an aim of the present invention is to provide a novel improved pneumatic cutting device able to carry out the cutting operations also on materials having considerable thickness and hardness while at the same time guaranteeing high oscillation velocity of the cutting blade and preventing the onset of vibrations or flexional stresses on the piston rod.

Further, another aim of the present invention is to provide a novel improved pneumatic cutting device able to provide an excellent thrust downwards on the rod stroke, and thus on the cutting blade, even in cases where the material to be cut is thick or hard, and without requiring an increase in the air flow rate of to be injected into the pneumatic supply system.

Lastly, another aim of the present invention is to provide a novel improved pneumatic cutting device having a more functional and less complex overall structure, and which thus enables a simplification at production level.

The above-cited aims are attained with an improved pneumatic cutting device having an oscillating blade for leather cutting machines according to the contents of claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristics of the improved pneumatic cutting device with an oscillating blade for leather cutting machines of the invention are described in the following with reference to the accompanying tables of drawings, in which:

- figures from 1A to 1C illustrate, in respective frontal views, the pneumatic cutting device described in the above-mentioned patent application cited and filed by the same Applicant, with the cutting blade represented in three different operating positions, respectively a lower cutting position (L1) in figure 1A, an intermediate cutting position (LM) in figure 1 B, and an upper cutting position (L2) in figure 1C;

- figure 2A illustrates, in larger scale, the view along section plane l-l of figure 1A; figure 2B illustrates, in larger scale, the view along section plane ll-ll of figure 1 B; and lastly figure 2C illustrates, in larger scale, the view along section plane Ill-Ill of figure 1C;

- figures from 3A to 3C illustrate, in respective frontal views, the improved pneumatic cutting device of the present invention, illustrated with the cutting blade represented in three different operating positions, respectively a lower cutting position (L1) in figure 3A, an intermediate cutting position (LM) in figure 3B, and an upper cutting position (L2) in figure 3C;

- figure 4A illustrates, in larger scale, the view along section plane IV-IV of figure 3A, figure 4B illustrates, in larger scale, the view along section plane V- V of figure 3B, and lastly figure 4C illustrates, in larger scale, the view along section plane VI-VI of figure 3C.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the appended tables of drawings, reference numeral (100) denotes the improved pneumatic cutting device with an oscillating blade for leather cutting machines of the present invention, in its entirety.

The improved pneumatic cutting device (100) comprises some of the same characteristics as the pneumatic cutting device of the above-mentioned and described patent application belonging to the same Applicant, in particular concerning the usual general characteristics present in pneumatic cutting devices.

Therefore, in the following description, the parts of the improved pneumatic cutting device (100) of the present invention that correspond to those described in the foregoing for the cutting device of the mentioned patent application will be indicated using the same references.

The improved pneumatic cutting device (100) therefore comprises a body (C), a cutting blade (L) for cutting a leather sheet stretched on a work plane (leather sheet and work plane not illustrated).

The improved pneumatic cutting device (100) in this regard is predisposed and configured so as to be mountable on cutting machines, for example numerically controlled.

The device is predisposed in such a way as to pneumatically activate the cutting blade (L) in order that it can oscillate vertically so as to score and cut the leather sheet.

Figures from 3A to 3C illustrate, in frontal views, the improved pneumatic cutting device (100), with the cutting blade (L) represented in different operating configurations attainable during oscillation thereof, respectively a lower cutting position (L1) (figure 3A), in which the cutting blade (L) crosses the whole thickness of the leather, an intermediate cutting position (LM) (figure 3B) in which the cutting blade (L) is internal of the thickness of the leather sheet, and an upper cutting position (L2) (figure 3C), in which the cutting blade (L) is substantially at the top of the leather sheet or slightly extracted from the leather.

The improved pneumatic cutting device (100) is also provided, internally of the body (C), with an oscillating chamber (1), with an upper end-run wall (11) and a lower end-run wall (12), and an oscillating piston (10).

The oscillating piston (10) comprises a head (13) and a rod (14), the oscillating piston (10) is predisposed with respect to the body (C) so that the head (13) thereof is inserted in the oscillating chamber (1), between the upper end-run wall (11) and the lower end-run wall (12), the rod (14) being connected to the cutting blade (L).

When the head (13) of the oscillating piston (10) is in abutment against the lower end-run wall (12) of the oscillating chamber (1), i.e. the cutting blade (L) is in the lower cutting position (L1), (see figure 4A), while when the head (13) of the oscillating piston (10) is in abutment against the upper end-run wall (11) of the oscillating chamber (1), the cutting blade (L) is in the upper cutting position (L2) (see figure 4C).

The upper end-run wall (11) is predisposed in the body (C) at a distance with respect to the lower end-run wall (12) so that, when the head (13) of the oscillating piston (10) is in abutment against the upper end-run wall (11), the cutting blade (L) reaches an upper cutting position (L2) such that it remains constantly in contact with the leather sheet to be cut, or slightly extracted with the aim of guaranteeing continuity to the cutting operation.

For the oscillation of the head (13) in the oscillating chamber (1), the cutting device (100) comprises a pneumatic activating system (P) comprising a pneumatic supply source (P1) (schematically illustrated by a continuous arrow line).

The pneumatic activating system (P) is configured so that a part (1A) of the oscillating chamber (1) comprised between the head (13) of the oscillating piston (10) and the lower end-run wall (12), and a part (1 B) of the oscillating chamber (1) comprised between the head (13) of the oscillating piston (10) and the upper end-run wall (11), are placed in communication alternatively with the pneumatic supply source (P1).

In this way, the head (13) is activated pneumatically to oscillate in the oscillating chamber (1) between the lower end-run wall (12) and the upper end-run wall (11), and therefore the rod (14), and consequently the cutting blade (L), are made to oscillate vertically between the lower cutting position (L1) of the leather sheet, when the head (13) of the oscillating piston (10) is in abutment against the lower end-run wall (12), and the upper cutting position (L2) of the leather sheet, when the head (13) of the oscillating piston (10) is in abutment against the upper end-run wall (11).

The special characteristics of the improved pneumatic cutting device of the present invention relate to the particular conformation of the rod and consequently also the particular conformation and configuration of the pneumatic activating system (P) responsible for the oscillation of the head (13) of the piston (10) in the oscillating chamber (1), and therefore responsible also for the vertical oscillation of the cutting blade (L), as described in detail in the following.

The body (C) is made in such a way as to comprise a first lower cylindrical cavity (162), inferiorly of the oscillating chamber (1), and a second upper cylindrical cavity (161), arranged superiorly of the oscillating chamber (1).

The rod (14) is realised in such a way as to comprise a first lower rod part (22), comprised between the head (13) of the oscillating piston (10) and the cutting blade (L), and arranged in such a way as to be able to slide in the first lower cylindrical cavity (162), and a second upper rod part (21), above the head (13) and arranged in such a way as to be able to slide in the second upper cylindrical cavity (161);

The pneumatic activating system (P) is conformed in such a way as to comprise:

a main annular switching chamber (30), realised in a portion of the walls of the second upper cylindrical cavity (161);

a main conduit (31) realised in the body (C) so as to place the pneumatic supply source (P1) in communication with the main annular switching chamber (30);

a discharge (SO) comprising an annular discharge chamber (40), realised in a portion of the walls of the second upper cylindrical cavity (161) superiorly of the main annular switching chamber (30), and a discharge conduit (41) realised in the body (C) so as place the annular discharge chamber (40) in communication with the outside of the body (C);

a secondary annular switching chamber (35), realised at the lower end-run wall (12) of the oscillating chamber (10), and in communication with the part (1A) of the oscillating chamber (1) comprised between the head (13) and the lower end-run wall (12);

an annular air passage hole (38), realised at the upper end-run wall (11) of the oscillating chamber (1) so as to place in communication the part (1 B) of the oscillating chamber (1) comprised between the head (13) and the upper end- run wall (11) in communication with the second upper cylindrical cavity (161).

In particular, the cutting device (100) of the invention is such that the second upper rod part (21) is conformed so as to comprise two annular projections (211 , 212), i.e. an upper annular projection (211) and a lower annular projection (212), and an annular recess (201) between the upper annular projection (211) and the lower annular projection (212), the upper annular projection (211) and the lower annular projection (212) being in sliding contact with the walls of the second upper cylindrical cavity (161).

The cutting device (100) of the invention is made in such a way that the rod (14) further has the special conformation as described in the following.

The rod (14) is made in such a way as to comprise:

a first internal conduit (24), internally of the second upper rod part (21) and having an initial upper part between the upper annular projection (211) and the lower annular projection (212), and a length that is such as to cross the head (13) of the oscillating piston (10) and to have a final lower part in an upper portion of the first lower rod part (22) below the head (13);

a first through-hole (25), realised between the upper annular projection (211) and the lower annular projection (212) of the second upper rod part (21), i.e. at a part of the annular recess (201), in order to place the first internal conduit (24) in communication with the outside of the second upper rod part (21); a second through-hole (26), realised in the final lower part of the first internal conduit (24) below the head (13) of the oscillating piston (10), so as to place the first internal conduit (24) in communication with the outside of the first lower rod part (22);

a second internal conduit (27), realised in the second upper rod part (21); a third through-hole (28) realised superiorly of the lower annular projection (212) of the second upper rod part (21), in a position such as to place the second internal conduit (27) in communication with the outside of the second upper rod part (21);

a fourth through-hole (29) realised superiorly of the upper annular projection

(211) of the second upper rod part (21), in a position such as to place the second internal conduit (27) in communication with the outside of the second upper rod part (21).

Other special aspects of the cutting device (100) of the invention consist in the fact that: the main annular switching chamber (30) and the annular discharge chamber (40) being mutually arranged, the annular recess (201) of the second upper rod part (21) having dimensions such that, the first through-hole (25) being positioned with respect to the annular recess (201) and the third through-hole (28) being positioned with respect to the lower annular projection

(212) and the second through-hole (26) being positioned with respect to the head (13), so that, with the alternating sliding of the second upper rod part (21) in the second upper cylindrical cavity (161).

When the annular recess (201) of the second upper rod part (21) is positioned at the main annular switching chamber (30), the upper annular projection (211) is interposed between the main annular switching chamber (30) and the annular discharge chamber (40), the first through-hole (25) is in communication with the main annular switching chamber (30), the second through-hole (26) is in communication with the secondary annular switching chamber (35) and the fourth through-hole (29) is in communication with the annular discharge chamber (40), (see figure 4A), so that the main conduit (31) is in communication, via the main annular switching chamber (30), the first through-hole (25), the first internal conduit (24) and the second through-hole (26), with the secondary annular switching chamber (35), and therefore the pneumatic supply source (P1) is in communication with the part (1A) of the oscillating chamber (1) comprised between the head (13) of the oscillating piston (10) and the lower end-run wall (12) (see the arrows with the continuous line, again in figure 4A), while the part (1 B) of the oscillating chamber (1), comprised between the head (13) of the oscillating piston (10) and the upper end-run wall (11), is in communication with the annular discharge chamber (40), and therefore with outside, through the annular air passage hole (38), the third through-hole (28), the second internal conduit (26) and the fourth through-hole (29) (see the arrows with the broken line in figure 4A), so that the oscillating piston (10) can be pneumatically pushed upwards; and when the annular recess (201) of the second upper rod part (21) is positioned at the first annular discharge chamber (40), the lower annular projection (212) is interposed between the annular discharge chamber (40) and the main annular switching chamber (30), the main annular switching chamber (30) is in communication with the annular air passage hole (38), the first through-hole (25) is in communication with the annular discharge chamber (40) (see figure 4C ), so that the main conduit (31) is in communication, via the main annular switching chamber (30), with the annular air passage hole (38), and therefore the pneumatic supply source (P1) is in communication with the part (1 B) of the oscillating chamber (1) comprised between the head (13) of the oscillating piston (10) and the upper end-run wall (11) (see the arrows with the continuous line, again in figure 4C ), while the part (1A) of the oscillating chamber (1), comprised between the head (13) of the oscillating piston (10) and the lower end-run wall (12), is in communication with the annular discharge chamber (40), and therefore with outside, through the second through-hole (26), the first internal conduit (24) and the first through-hole (25) (see the arrows with the broken line, again in figure 4C ), so that the oscillating piston (10) can be pneumatically pushed downwards.

Figure 4B illustrates instead the situation in an intermediate position of the oscillating piston (10) with respect to the end positions illustrated in figures 4A and 4C, with figure 4A, which, as described herein above, illustrates the head (13) of the oscillating piston (10) in abutment against the lower end-run wall (12), while figure 4C, which, as described herein above, illustrates the head

(13) of the oscillating piston (10) in abutment against the upper end-run wall (11).

In the position of figure 4B, the main annular switching chamber (30) is closed by the lower annular projection (212) of the second upper rod part (21), while the annular discharge chamber (40) is closed by the upper annular projection (211) of the second upper rod part (21).

Consequently the oscillating piston (10) can continue in the upwards run thereof, if starting from the configuration illustrated in figure 4A, or can continue in the downwards run, if starting from the configuration illustrated in figure 4C.

Owing to the combination of the special characteristics as defined in the foregoing, in particular the special conformation of the rod (14), which comprises a first lower rod part (22), below the head (13), and a second upper rod part (21), above the head (13), and also due to the special conformation of the pneumatic activating system (P), which are correlated to the particular conformation of second upper rod part (21), the improved pneumatic cutting device (100) of the present invention enabling the following advantages to be obtained.

The features for the functions of switching the oscillating piston stroke are all realised in the second upper rod part (21), i.e. above the head (13) of the oscillating piston (10) and thus above the oscillating chamber (1), and all the parts of the pneumatic activating system (P) responsible for the switching of the piston stroke are correspondingly realised above the head (13) of the oscillating piston (10), i.e. at the second upper cylindrical cavity (161) of the body (C).

This enables having the first lower rod part (22) between the head (13) and the cutting blade (L), with no machining, i.e. without the need for recesses and projections, as instead occurred in the cutting device of the prior art described in the foreword and illustrated in figures from 1 A to 1C, and from 2A to 2C.

Further, the part of the body (C) in which the first lower rod part (22) is to slide, i.e. the first lower cylindrical cavity (162), will consequently also have no machining, i.e. will be free of cavities/annular chambers to be used for the pneumatic switching.

Consequently, the first lower rod part will be stiffer and will be able to withstand the stresses deriving from cutting operations carried out on thick and hard materials, without incurring the risk of any eventual snagging as was liable to happen with the cutting device of known type described in the foreword.

Further, the pneumatic activating system (P) is provided with only two annular chambers realised in the walls of the second upper cylindrical cavity (162) of the body (C), i.e. the main annular switching chamber (30) and the annular discharge chamber (40).

This is made possible due to the presence of the two internal conduits (24, 27) realised in the second upper rod part (21), and of the secondary annular switching chamber (35), realised at the lower end-run wall (12) of the oscillating chamber (10).

This enables realising one discharge (SO) only, instead of two, as in the case of the prior-art device described in the foregoing.

Consequently, the machining operations necessary for realising the second upper cylindrical cavity (161) of the body (C), and for realising the second upper rod part (21), will be substantially simplified with respect to the prior-art device of the patent application cited in the preamble.

Further, the pneumatic flow path is more linear since from the main annular switching chamber (30) it can flow directly into the part (1A) of the oscillating chamber (10) comprised between the lower end-run wall (12) and the piston head (10) due to the first internal conduit (24) of the second upper rod part (21), and therefore the pneumatic activation is more efficient, especially at high velocity.

Further and other characteristics of the improved cutting device of the invention are described in the following. The second upper cylindrical cavity (161) is realised in the body (C) in such a way as to have a greater height than the height of the second upper rod part (21).

In this way, during the alternating sliding of the second upper rod part (21) in the second upper cylindrical cavity (161), when the head (13) of the oscillating piston (10) is in abutment against the upper end-run wall (11), the upper end of the second upper rod part (21) remains distant from the upper end of the second upper cylindrical cavity (161) so as to define between them a thrust chamber (33).

Further, the fourth through-hole (29) is realised in a portion of the second upper rod part (21) above the upper annular projection (211).

In this way, when the annular recess (201) of the second upper rod part (21) is positioned at the annular discharge chamber (40), the lower annular projection (212) being interposed between the annular discharge chamber (40) and the main annular switching chamber (30) and with the third through-hole (28) at the main annular switching chamber (30), the upper annular projection (211) is located above the annular discharge chamber (40) and the fourth through-hole

(29) is located at the thrust chamber (33).

In this situation, the above-mentioned thrust chamber (33) is in communication, via the fourth through-hole (29), the second internal conduit (27) and the third through-hole (28) and the main annular switching chamber

(30), with the pneumatic supply source (P1).

This enables a part of pneumatic supply flow to be directed into the thrust chamber (33) in order to provide a further downwards pneumatic thrust of the oscillating piston (10).

Owing to having sub-divided the rod (14) into two parts, with the second upper rod part (21), above the head (13) of the piston (10), which is responsible for the switching of the oscillation of the piston (10), it is possible to realise the lower rod part (22) so that it has a smaller diameter than the diameter of the upper rod part (21). In this way, even in cases where significant run entities are to be made, i.e. greater than 1.5 m , a first lower rod part (22) can be made that is sufficiently long to reach the desired entity of the oscillation run, and which however has, at the same time, a modest weight, as it can be made with a smaller diameter with respect to the diameter of the second upper rod part (21).

Having a first lower rod part (22) with a smaller section, and therefore also a modest weight, further enables imparting a greater upwards thrust on the oscillating piston (10).

The portion of the upper rod part (21) between the lower annular projection (212) and the head (13) of the oscillating piston (10) has a smaller diameter than the diameter of the second upper cylindrical cavity (161).

In this way, an annular air passage channel (39) can be defined there between, in order to facilitate the passage of the flow of pneumatic supply from the main annular switching chamber (30) to the annular air passage hole (38) when, with the sliding of the second upper rod part (21) in the second upper cylindrical cavity (161), the annular recess (201) of the second upper rod part (21) is positioned at the annular discharge chamber (40), the lower annular projection (212) being interposed between the annular discharge chamber (40) and the main annular switching chamber (30), and the head (13) of the oscillating piston (10) being in abutment against the upper end-run wall (11) (figure 4C).

Owing also this last special feature, the flow path of the pneumatic supply has been further optimised, enabling an effective switching of the oscillation stroke of the oscillating piston to be made even at high velocities.




 
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