EP3619329B1

EP3619329B1 - A pneumatic cutting device having an oscillating blade for leather sheet cutting machines

Info

Publication number: EP3619329B1
Application number: EP18728230.6A
Authority: EP
Inventors: Gianni Gallucci
Original assignee: Teseo SpA
Current assignee: Teseo SpA
Priority date: 2017-05-02
Filing date: 2018-04-27
Publication date: 2021-03-31
Anticipated expiration: 2038-04-27
Also published as: EP3619329A1; WO2018203199A1; CN110582583A; CN110582583B; IT201700046921A1

Description

FIELD OF THE INVENTION

The present invention relates to the particular technical sector concerning cutting machines for cutting sheet or rolled materials, such as skins, leathers, hides, synthetic leather, etc.
In particular, the present invention relates to a cutting device having a pneumatically-powered oscillating blade destined to be mounted on the cutting machines.

DESCRIPTION OF THE PRIOR ART

Cutting machines comprise a frame, which is predisposed on a work plane, where the materials to be cut are laid out, such as for example skins (hides, leather), synthetic skins and the like, and mounted on the frame are a cutting device inferiorly provided with a cutting blade, and movement means, 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 so that the cutting blade can be positioned above the skins, 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 or desired profiles and/or 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 material, from a lower cutting position to an upper cutting position, always remaining within the thickness of the material to be scored/cut.
For this purpose, at present cutting devices powered pneumatically are particularly used to cause the cutting blade to perform the requested oscillation needed to perform the cut.
These pneumatically activated cutting devices comprise an oscillating chamber, having an upper stroke limit wall and a lower stroke limit wall, an oscillating piston, predisposed with the head thereof inserted in the oscillating chamber and with the relative rod thereof connected to the cutting blade, and a pneumatic activating system communicating with the oscillating chamber in order to cause the piston to oscillate between the upper stroke limit wall and the lower stroke limit wall, and therefore to cause the cutting blade to oscillate vertically.
In known cutting devices, the pneumatic activating system comprises a pneumatic activating system and a discharge, which are predisposed and configured in such a way that the part of the oscillating chamber comprised between the piston head and the upper stroke limit wall and the part of the oscillating chamber comprised between the piston head and the lower stroke limit wall are alternatingly communicating with the pneumatic activating system and with the discharge so as to make the oscillation of the piston possible inside the oscillating chamber.
In particular, when the pneumatic supply is placed in communication with the part of the oscillating chamber comprised between the piston head and the upper stroke limit surface, the part of the oscillating chamber comprised between the piston head and the lower stroke limit surface is in communication with the discharge; in this case the piston is pushed pneumatically downwards; while when the pneumatic supply is placed in communication with the part of the oscillating chamber comprised between the piston head and the lower stroke limit surface, the part of the oscillating chamber comprised between the piston head and the upper stroke limit surface is in communication with the discharge, and in this case the piston is pushed pneumatically upwards, thus generating an oscillating motion of the piston head inside the oscillating chamber and thus the vertical oscillation of the cutting blade.
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 a respectively in communication with the openings and with the respective shutters or other valve members 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.
The switching of the oscillation of the piston is done by means of use of appropriate valve members 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 stroke.
This circumstance can have a negative effect on the effectiveness of the cut.
A particularly significant requirement in this specific sector relates to the oscillation velocity of the piston: high oscillation velocities guarantee a greater cutting efficiency and high productivity (the leather sheet cutting operations can be carried out in shorter times).
Document WO2015/154830 discloses a pneumatic cutting device for leather sheet cutting machines according to the preamble of claim 1 and which does not necessitate the use of external switching members for switching the oscillation of the oscillating piston since this oscillation is obtained automatically.
Document CN 201778031 U discloses a pneumatic cutting device according to another prior art solution wherein the oscillation of the piston is obtained automatically.
EP3436612 A1 , which is considered to represent prior art according to Art. 54(3) EPC disclosesa pneumatic cutting device having an oscillating blade for leather sheet cutting machines, comprising: a body; a cutting blade for cutting a leather sheet stretched on a work plane; an oscillating chamber, internal of the body, comprising an upper end- run wall and a lower end-run wall; an oscillating piston, having a head and a rod, the oscillating piston being predisposed with the head thereof inserted in the oscillating chamber, between the upper end-run wall and the lower end-run wall, the rod being connected to the cutting blade; a pneumatic activating system communicating with the oscillating chamber, the pneumatic activating system comprising a source of pneumatic power supply and at least a discharge which are predisposed and configured so that a first part of the oscillating chamber comprised between the head of the oscillating piston and the lower end-run wall, and a second part of the oscillating chamber comprised between the head of the oscillating piston and the upper end-run wall, are placed in communication alternatingly with the source of pneumatic power supply and with the at least a discharge so as to activate the oscillating piston to oscillate inside the oscillating chamber between the lower end-run wall and the upper end-run wall, and therefore cause the cutting blade to oscillate vertically between a lower cutting position of the leather sheet and an upper cutting position of the leather sheet, the upper end-run wall being predisposed in the body with respect to the lower end-run wall so that when the cutting blade reaches the upper cutting position during the vertical oscillation thereof, it remains in contact with the leather sheet to be cut; the body comprising a cylindrical cavity and the rod of the oscillating piston which is predisposed so as to be slidable alternatingly in the cylindrical cavity; the rod of the oscillating piston being conformed so as to have: two annular portions, in sliding contact with the walls of the cylindrical cavity, an annular recess, comprised between the two annular portions, and an internal conduit, the rod being provided with through-holes which are predisposed along the rod in a position below the annular recess and such as to place the internal conduit in contact with the outside of the rod; the head of the oscillating piston being provided with at least a hole predisposed so as to place the internal conduit of the rod in communication with the second part of the oscillating chamber comprised between the head of the oscillating piston and the upper end-run wall of the oscillating chamber; the pneumatic activating system comprising: a switching chamber of the oscillation of the oscillating piston comprising an upper annular chamber and a lower annular chamber realised in a portion of the walls of the cylindrical cavity; a main conduit predisposed in the body so as to be in communication with the source of pneumatic power supply and with a part of the lower annular chamber of the switching chamber; a secondary conduit predisposed in the body so as to place the upper annular chamber of the switching chamber in communication with the oscillating chamber via a passage hole in the lower end-run wall of the oscillating chamber; an upper discharge communicating with outside and a lower discharge communicating with the outside; the upper discharge comprising a first annular discharge chamber made in a portion of the walls of the cylindrical cavity above the upper annular chamber of the switching chamber and a first discharge conduit made in the body so as to place the first annular discharge chamber in communication with outside; the lower discharge comprising a second annular discharge chamber made in a portion of the walls of the cylindrical cavity below the lower annular chamber of the switching chamber and a second discharge conduit made in the body so as to place the second annular discharge chamber in communication with outside; the annular recess of the rod having dimensions so that, and with the holes of the rod being positioned with respect to the annular recess in such a way that, with the alternating sliding of the rod in the cylindrical cavity: when the annular recess of the rod is positioned at the switching chamber so as to place the lower annular chamber and the upper annular chamber in mutual communication, the holes of the rod are positioned at the second annular discharge chamber, so that the main conduit is in communication, via the lower annular chamber, the annular recess and the upper annular chamber, with the secondary conduit and therefore the source of pneumatic power supply is in communication with the first part of the oscillating chamber between the head of the oscillating piston and the lower end-run wall, while the second part of the oscillating chamber comprised between the head of the oscillating piston and the upper end-run wall is in communication with the second annular discharge chamber; and then via the second discharge conduit with the outside, through the hole of the head of the piston, the internal conduit of the rod and the holes of the rod, so that the oscillating piston can be pushed pneumatically upwards; and when the annular recess of the rod is positioned both at the first annular discharge chamber of the upper discharge and the upper annular chamber of the switching chamber communicating with the secondary conduit, the holes of the rod are at the lower annular chamber of the switching chamber and therefore communicating with the main conduit, so that the source of pneumatic power supply, via the main conduit, the holes of the rod, the internal conduit of the rod and the hole present in the head of the oscillating piston, is in communication with the second part of the oscillating chamber between the upper end-run wall and the head of the oscillating piston, while the first part of the oscillating chamber between the head of the oscillating piston and the lower end-run wall is in communication with the first annular discharge chamber via the secondary conduit, the upper annular chamber of the switching chamber and the annular recess, and then via the first discharge conduit with the outside, so that the oscillating piston can be pushed pneumatically downwards.

SUMMARY OF THE INVENTION

An aim of the present invention is therefore to disclose a new pneumatic cutting device having an oscillating blade for leather sheet cutting machines able to guarantee high oscillation velocity of the cutting blade.
A further aim of the present invention is to disclose a pneumatic cutting device having an oscillating blade in which there is no requirement and dependency on external switching members for switching the oscillation of the oscillating piston.
The above-cited aims are attained with a pneumatic cutting device having an oscillating blade for leather sheet cutting machines according to the contents of claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

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

figures 1A and 1B illustrate the pneumatic cutting device with an oscillating blade for leather sheet cutting machines, object of the invention, in two distinct operating configurations of the oscillating blade during activation in oscillation thereof so as to cut a leather sheet, where figure 1A illustrates the lower cutting position reachable by the blade during oscillation thereof, while figure 1B illustrates the upper cutting position reachable by the blade during oscillation thereof;
figure 2A is a view along section plane I-I of figure 1A, in larger scale;
figure 2B is a view along section plane II-II of figure 1B, in larger scale;
figure 2C illustrates, in a view in transversal section, as in the previous figures, the cutting device of the invention with the blade in an intermediate position between the lower cutting position and the upper cutting position;
figure 3A illustrates a part of the cutting device with the oscillating blade of the invention, with the oscillating piston not illustrated in such a way as to highlight other significant internal components which are illustrated using broken lines;
figure 3B is a view along section plane III-III of figure 3A;
figure 3C is a view along section plane IV-IV of figure 3A.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the appended tables of drawings, reference numeral (100) denotes the pneumatic cutting device with oscillating blade for leather sheet cutting machines of the present invention, in its entirety.
The pneumatic cutting device (100) of the invention comprises a body (C), a cutting blade (L) for cutting a leather sheet (V) (or another like material in sheets or rolls, such as leather or synthetic materials) which is stretched on a work plane (not illustrated in the drawings).
The pneumatic cutting device (100) in this regard is mountable on cutting machines, for example numerically controlled.
It 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 (V).
In this regard, the cutting device (100) is provided, internally of the body (C), with an oscillating chamber (1), with an upper stroke limit wall (11) and a lower stroke limit wall (12), and 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 stroke limit wall (11) and the lower stroke limit wall (12), the rod (14) being connected to the cutting blade (L).
For the pneumatic activating of the vertical oscillation of the cutting blade (L), the pneumatic cutting device (100) is provided with a suitable pneumatic activating system (P) communicating with the oscillating chamber (1).
The pneumatic activating system (P) comprises a pneumatic supply source (P1) (for example compressed air, denoted schematically by arrow (P1)) and at least a discharge (S1, S2).
The source of pneumatic power supply (P1) and the at least a discharge (S1, S2) are predisposed and configured so that a first part (1A) of the oscillating chamber (1) comprised between the head (13) of the oscillating piston (10) and the lower stroke limit wall (12) and a second part (1B) 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) and with the at least a discharge (S1, S2), so as to pneumatically activate 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),
The pneumatic activating system (P) present in the cutting device (100) is able to pneumatically activate 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, consequently, to cause the cutting blade (L) to oscillate vertically.
In particular, the cutting blade (L) is thus caused to oscillate vertically between a lower cutting position (L1) (see figure 1A) defined when the head (13) of the oscillating piston (10) is in abutment against the lower stroke limit wall (12) of the oscillating chamber (1) (see figure 2A), and an upper cutting position (L2) (see figure 1B), defined when the head (13) of the oscillating piston (10) is in abutment against the upper stroke limit wall (11) of the oscillating chamber (1) (see figure 2B).
For this purpose, the cutting device (100) is such that the upper stroke limit wall (11) is predisposed in the body (C) at a distance with respect to the lower stroke limit wall (12) so that, when the head (13) of the oscillating piston (10) is in abutment against the upper stroke limit wall (11), the cutting blade (L) reaches an upper cutting position (L2) such that it remains constantly in contact with the leather sheet (V) to be cut, with the aim of guaranteeing continuity to the cutting operation.
The peculiarities of the present invention consist in the special structure and configuration of the pneumatic activating system (P) which enables causing the cutting blade (L) to oscillate at an oscillation velocity that is higher than with the cutting devices of known type, and which, moreover, does not require the use of any valve member or external switching shutter.
The body (C) comprises a cylindrical cavity (16) while 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 so as to have: two annular portions (141, 142), in sliding contact with the walls of the cylindrical cavity (16), an annular recess (140), which is comprised between the two annular portions (141, 142), and an internal conduit (17), the rod (14) which is further provided with through-holes (18) which are predisposed along the rod (14) in a position below the annular recess (140) 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 second part (1B) 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);
a main conduit (81) which is realised and predisposed in the body (C) so as to be in communication with the pneumatic supply source (P1) and 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);
an upper discharge (S1) communicating with outside and a lower discharge (S2) communicating with the outside.

In greater detail, the upper discharge (S1) comprises a first annular discharge chamber (91), which 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 a first discharge conduit (92), which is realised and predisposed in the body (C) so as to place the first annular discharge chamber (91) in communication with outside;
while the lower discharge (S2) comprises a second annular discharge chamber (93) which 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 a second discharge conduit (94) which is made and predisposed in the body (C) so as to place the second annular discharge chamber (93) in communication with outside.
Further, the annular recess (140) of the rod (14) having dimensions so that, and with the holes (18) of the rod (14) being positioned 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 mutual communication, the holes (18) of the rod (14) are positioned at the second annular discharge chamber (93) (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 source of pneumatic power supply (P1) is in communication with the first part (1A) of the oscillating chamber (1) between the head (13) of the oscillating piston (10) and the lower end-run wall (12) (see the arrows in the unbroken lines in figure 2A ), while the second part (1B) 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 second annular discharge chamber (93), 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 in broken lines in figure 2A ), so that the oscillating piston (10) can be pneumatically pushed upwards;
and when the annular recess (140) of the rod (14) is positioned both at the first annular discharge chamber (91) of the upper discharge (S1) and 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 therefore communicating with the main conduit (81) (see figure 2B ), so that the source of pneumatic power supply (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 second part (1B) of the oscillating chamber (1) between the upper end-run wall (11) and the head (13) of the oscillating piston (10) (see the arrows with unbroken lines in figure 2B ), while the first part (1A) of the oscillating chamber (1) between the head (13) of the oscillating piston (10) and the lower end-run wall (12) is in communication with the first annular discharge chamber (91) of 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 2B ), in such a way that the oscillating piston (10) can be pneumatically pushed downwards.

Lastly, a further particularly significant peculiarity of the pneumatic cutting device of the present invention consists in the fact that at least one between the first discharge conduit (92) and the second discharge conduit (94) has a transversal section that is greater than the transversal section of the main conduit (81).
Owing to this particular specification, the part of the oscillating chamber that is placed in communication with the discharge conduit having the transversal section larger than the transversal section of the main conduit empties more rapidly with respect to the filling of the part of the oscillating chamber that is placed in communication with the main conduit, i.e. with the pneumatic supply source.
In other words, at the moment of switching the oscillation of the piston stroke, the quantity of air that exits from the part of the oscillating chamber in communication with the discharge conduit which has a transversal section that is larger than the transversal section of the main conduit is greater than the quantity of air that enters into the part of the oscillating chamber communicating with the pneumatic supply source: in this way the effective pressure resulting on the oscillating piston head is significantly greater than in the prior art.
Consequently an acceleration is produced that is greater on the piston, and therefore a greater velocity of the oscillation stroke of the cutting blade.
For example, in a further embodiment, it can be the first discharge conduit (92) (i.e. the one on the upper discharge (S1)) that has a transversal section larger than the transversal section of the main conduit (81).
In this case, when the oscillating piston (10) goes into abutment against the upper end-run wall (11), i.e. it determines the situation illustrated in figure 2B, i.e. the annular recess (140) of the rod (14) is positioned both at the first annular discharge chamber (91) of the upper discharge (S1) and the upper annular chamber (8A) of the switching chamber (8) communicating with the secondary conduit (82), while the holes (18) of the rod (14) are at the lower annular chamber (8B) of the switching chamber (8) and therefore communicating with the main conduit (81), then:

the first part (1A) of the oscillating chamber (1) between the head (13) of the oscillating piston (10) and the lower end-run wall (12) is in communication with the first annular discharge chamber (91) 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,
while the source of pneumatic power supply (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 second part (1B) of the oscillating chamber (1) between the upper end-run wall (11) and the head (13) of the oscillating piston (10).

In this situation, therefore, the first part (1A) of the oscillating chamber (1) between the head (13) of the oscillating piston (10) and the lower end-run wall (12) is in communication with the outside via the first discharge conduit (92) which has a transversal section that is greater than the transversal section of the main conduit (81), which is instead in communication with the second part (1B) of the oscillating chamber (1) between the head (13) of the oscillating piston (10) and the upper end-run wall (11): this means that the quantity of air that can exit from first part (1A) of the oscillating chamber (1) is greater than the quantity that can enter the second part (1B) of the oscillating chamber.
In this way, an effective pressure is applied on the oscillating piston head (10), which pushes it downwards, than is applied using the prior art.
Consequently, a greater acceleration is impressed downwards on the cutting blade, and therefore an oscillation stroke having a greater velocity from the upper cutting point (L2) to the lower cutting point (L1).
Instead, in a case in which, in a further embodiment, the cutting device (100) is predisposed in such a way that it is the second discharge conduit (94) (i.e. the conduit of the lower discharge (S2)) that has a transversal section that is greater than the transversal section of the main conduit (81), the situation is inverted.
In this case, when the oscillating piston (10) goes into abutment against the lower end-run wall (12), i.e. it determines the situation illustrated in figure 2A, i.e. 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 mutual communication, the holes (18) of the rod (14) are positioned at the second annular discharge chamber (93), then:

the second part (1B) of the oscillating chamber (1), between the head (13) of the oscillating piston (10) and the upper stroke limit wall (11) is in communication with the second annular discharge chamber (93), 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);
while the source of pneumatic power supply (P1) is in communication with the first part (1A) of the oscillating chamber (1) between the head (13) of the oscillating piston (10) and the lower end-run wall (12), via the main conduit (81), which is in communication, via the lower annular chamber (8B), the annular recess (140) and the upper annular chamber (8A), with the secondary conduit (82) that opens via the passage hole (83) into the first part (1A) of the oscillating chamber (1).

In this situation, therefore, the second part (1B) of the oscillating chamber (1) between the head (13) of the oscillating piston (10) and the upper end-run wall (11), is in communication with the outside via the second discharge conduit (94) which has a transversal section that is greater than the transversal section of the main conduit (81), which is instead in communication with the first part (1A) of the oscillating chamber (1) between the head (13) of the oscillating piston (10) and the lower end-run wall (12): this means that the quantity of air that can exit from the second part (1B) of the oscillating chamber (1) is greater than the quantity that can enter the first part (1A) of the oscillating chamber (1).
In this way, an effective pressure is applied on the head of the oscillating piston head (10), which pushes it upwards, that is greater than what is applied using the prior art devices.
Consequently, a greater acceleration is impressed upwards on the cutting blade (L), and therefore an oscillation stroke having a greater velocity from the lower cutting point (L1) to the upper cutting point (L2).
According to a preferred and particularly advantageous embodiment, such as the one illustrated in the appended figures, the cutting device (100) of the invention can be predisposed and configured so that both the first discharge conduit (92) and the second discharge conduit (94) have a transversal section that is greater than the transversal section of the main conduit (81).
In this case, at each end of the oscillating piston stroke (10), both upper and lower, the quantity of air exiting towards the outside from the part of the oscillating chamber (1) placed in communication with the relative discharge (for the upper stroke end it is the first part (1A) of the oscillating chamber (1) that is in communication with the first discharge conduit (92) of the upper discharge (S1), see figure 2B , while for the lower stroke end it is the second part (1B) of the oscillating chamber (1) that is in communication with the second discharge conduit (94) of the lower discharge (S2), see figure 2A ), is always greater than the quantity of air injected into the other part of the oscillating chamber (1) placed in communication with the source of pneumatic power supply (P1) (for the upper stroke end it is the second part (1B) of the oscillating chamber (1) that is in communication with the main conduit (81), see figure 2B , while for the lower stroke end it is the first part (1A) of the oscillating chamber (1) that is in communication with the main conduit (81), see figure 2A ).
In this way, for each switching of the oscillating piston (10) stroke, i.e. each time the oscillating piston (10) reaches the stroke end thereof, either upper or lower, the cutting device (100) is able to impress thereon a considerable thrust acceleration, certainly greater than in the case of the prior art.
Consequently, and owing to these particular specifications, oscillation velocities of the cutting blade (L) can be reached, between the lower cutting point (L1) and the upper cutting point (L2), that are decidedly greater than those of the prior-art pneumatic devices.
More preferably, in order to improve performance, both the first discharge conduit (92) and the second discharge conduit (94) have a transversal section that is greater than the transversal section of the main conduit (81), and have a substantially identical section.
According to possible embodiments, all falling within the scope of the present invention, the cutting device (100) can preferably be predisposed and configured in such a way that at least one from between the first discharge conduit (92) and the second discharge conduit (94) has a transversal section that is greater than and as a maximum up to five times of the transversal section of the main conduit (81), in particular a section between two and three times the transversal section of the main conduit (81), and more in particular a section between two and four times the transversal section of the main conduit (81).
Particularly preferred embodiments of the cutting device according to the invention are those in which both the first discharge conduit (92) and the second discharge conduit (94) have a transversal section that is greater than and maximally up to five times the transversal section of the main conduit (81), in particular a section between two and three times the transversal section of the main conduit (81), and more in particular a section between two and four times the transversal section of the main conduit (81).
For example, in a particularly preferred embodiment the cutting device (100) is predisposed and configured so that the main conduit (81) includes a circular transversal section with a 2 mm diameter, while both the first discharge conduit (92) and the second discharge conduit (94) in turn have a circular transversal section that having a 4 mm diameter, i.e. the transversal section thereof is four times the section of the main conduit (81).
In this case, considering for example that the compressed air supply pressure coming from the pneumatic supply source (P1) is 6 bar, at each stroke end the part of the oscillating chamber communicating with the relative discharge conduit has a residual pressure of about 1 bar: consequently, on the head of the oscillating piston (in the part of the oscillating chamber that is connected to the source of pneumatic power supply) an effective pressure of about 5 bar acts to produce a thrust acceleration on the piston of about 2.5 times greater with respect to the prior art cases in which the sections of the two communication openings are substantially identical.
By way of example, in the following a possible operating cycle of the pneumatic cutting device (100) of the invention is described, starting for example from the situation illustrated in figure 2A in which the source of pneumatic power supply (P1) is active and the oscillating piston (10) is located with the relative head (13) in contact with the lower stroke limit wall (12) of the oscillating chamber (1), i.e. with the cutting blade (L) located in the lower cutting position (L1).
In this situation, the rod (14) of the oscillating piston (10), with respect to the walls of the cylindrical cavity (16) of the body (C), is located in a position such that 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 mutual communication, thus placing the main conduit (81) in communication with the secondary conduit (82), while the holes (18) of the rod (14) are positioned at the second annular discharge chamber (93) of the lower discharge (S2).
Therefore, the source of pneumatic power supply (P1), via the main conduit (81), the lower annular chamber (8B), the annular recess (140) and the upper annular chamber (8A), the secondary conduit (82) and the passage hole (83), is in communication with the first part (1A) of the oscillating chamber (1) comprised between the head (13) of the oscillating piston (10) and the lower wall (12) of the oscillating chamber (1), while the second part (1B) of the oscillating chamber (1) comprised between the head (13) of the oscillating piston (10) and the upper wall (11) of the oscillating chamber (1), via the hole (130) of the head (13), the internal conduit (17) of the rod (14) and the holes (18) of the rod (14) itself, is in communication with the second annular discharge chamber (93) of the lower discharge (S2).
The pneumatic flow coming from the pneumatic supply source (P1) thus arrives in the first part (1A) of the oscillating chamber (1), below the head (13) of the oscillating piston (10), pushing it consequently upwards, as the second part (1B) of the oscillating chamber (1), above the head (13) of the oscillating piston (10), is connected to the lower discharge (S2).
The oscillating piston (10) is thus pushed upwards, with a contemporaneous upwards sliding of the rod (14) thereof in the cylinder (16) and an upwards displacement of the cutting blade (L).
When the head (13) of the oscillating piston (10) is in abutment against the upper stroke limit wall (11) of the oscillating chamber (1) (see figure 2B), the cutting blade (L) reaches the upper cutting position (L2) thereof, while the upwards sliding of the rod (14) in the cylindrical cavity (16) of the body (C) determines the following condition:
the holes (18) of the rod (14) are at the lower annular chamber (8B) of the switching chamber (8) and therefore communicating with the main conduit (81), the recess (140) of the rod (14) is positioned both at the first annular discharge chamber (91) of the upper discharge (S1) and the upper annular chamber (8A) of the switching chamber (8) and thus communicates with the secondary conduit (82).
In this situation, the main conduit (81), via 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 second part (1B) of the oscillating chamber (1) comprised between the head (13) of the oscillating piston (10) and the upper wall (11) of the oscillating chamber (1), while the first part (1A) of the oscillating chamber (1) below the head (13) of the oscillating piston (10), via the passage hole (83), the secondary conduit (82), the upper annular chamber (8A) of the switching chamber (8) and the annular recess (140) is in communication with the first annular discharge chamber (91) of the upper discharge (S1).
Therefore, the pneumatic flow coming from the pneumatic supply source (P1) thus reaches the second part (1B) of the oscillating chamber (1), above the head (13) of the oscillating piston (10), consequently pushing it downwards, as the first part (1A) of the oscillating chamber (1), above the head (13) of the oscillating piston (10), is connected to the upper discharge (S1): the oscillating piston (10) is thus pushed downwards, with a contemporaneous downwards sliding of the rod (14) thereof in the cylindrical cavity (16) and a downwards displacement of the cutting blade (L), in order to return into the preceding situation in figure 2A, i.e. into the lower cutting position (L1) thereof (figure 1A).
The above-described cycle is repeated as long as the source of pneumatic power supply (P1) is active, thus causing the oscillation of the cutting blade (L) between the lower cutting position (L1) and the upper cutting position (L2) thereof.
A further advantageous aspect of the pneumatic cutting device of the present invention is constituted by the special structure and configuration of the pneumatic activating system, which enables, as described in the foregoing, the switching of the oscillation of the piston to be activated and determined by the piston itself, according to the position of the relative rod with respect to the walls of the cylindrical cavity, and in particular with respect to the lower annular chamber and the upper annular chamber of the switching chamber and the first annular chamber and the second annular chamber of the two discharges, as described in detail herein above.

Claims

A pneumatic cutting device (100) having an oscillating blade for leather sheet 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) communicating with the oscillating chamber (1), the pneumatic activating system (P) comprising a source of pneumatic power supply (P1) and at least a discharge (S1, S2) which are predisposed and configured so that a first 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 second part (1B) 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 source of pneumatic power supply (P1) and with the at least a discharge (S1, S2) so as to activate 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 cutting blade (L) to oscillate vertically between a lower cutting position (L1) of the leather sheet (V) and an upper cutting position (L2) of the leather sheet (V),

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

the body (C) comprising a cylindrical cavity (16) and the rod (14) of the oscillating piston (10) which is predisposed so as to be slidable alternatingly in the cylindrical cavity (16); and characterized in that:
the rod (14) of the oscillating piston (10) being conformed so as to have: two annular portions (141, 142), 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) being provided with through-holes (18) which are predisposed along the rod (14) in a position below the annular recess (140) 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) being provided with at least a hole (130) predisposed so as to place the internal conduit (17) of the rod (14) in communication with the second part (1B) 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) comprising:
a switching chamber (8) of the oscillation of the oscillating piston (10) comprising an upper annular chamber (8A) and a lower annular chamber (8B) realised in a portion of the walls of the cylindrical cavity (16);

a main conduit (81) predisposed in the body (C) so as to be in communication with the source of pneumatic power supply (P1) and with a part of the lower annular chamber (8B) of the switching chamber (8);

a secondary conduit (82) 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) in the lower end-run wall (12) of the oscillating chamber (1);

an upper discharge (S1) communicating with outside and a lower discharge (S2) communicating with the outside;

the upper discharge (S1) comprising a first annular discharge chamber (91) made in a portion of the walls of the cylindrical cavity (16) above the upper annular chamber (8A) of the switching chamber (8) and a first discharge conduit (92) made in the body (C) so as to place the first annular discharge chamber (91) in communication with outside;

the lower discharge (S2) comprising a second annular discharge chamber (93) made in a portion of the walls of the cylindrical cavity (16) below the lower annular chamber (8B) of the switching chamber (8) and a second discharge conduit (94) made in the body (C) so as to place the second annular discharge chamber (93) in communication with outside;

the annular recess (140) of the rod (14) having dimensions so that, and with the holes (18) of the rod (14) being positioned 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):
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 mutual communication, the holes (18) of the rod (14) are positioned at the second annular discharge chamber (93), 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 source of pneumatic power supply (P1) is in communication with the first part (1A) of the oscillating chamber (1) between the head (13) of the oscillating piston (10) and the lower end-run wall (12), while the second part (1B) 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 second annular discharge chamber (93); 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), so that the oscillating piston (10) can be pushed pneumatically upwards;

and when the annular recess (140) of the rod (14) is positioned both at the first annular discharge chamber (91) of the upper discharge (S1) and 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 therefore communicating with the main conduit (81), so that the source of pneumatic power supply (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 second part (1B) of the oscillating chamber (1) between the upper end-run wall (11) and the head (13) of the oscillating piston (10), while the first part (1A) of the oscillating chamber (1) between the head (13) of the oscillating piston (10) and the lower end-run wall (12) is in communication with the first annular discharge chamber (91) 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, so that the oscillating piston (10) can be pushed pneumatically downwards,

wherein at least one between the first discharge conduit (92) and the second discharge conduit (94) has a transversal section that is greater than the transversal section of the main conduit (81).
The pneumatic cutting device of claim 1, wherein both the first discharge conduit (92) and the second discharge conduit (94) have a transversal section that is greater than the transversal section of the main conduit (81).
The pneumatic cutting device of claim 2, wherein the first discharge conduit (92) and the second discharge conduit (94) have a transversal section substantially identical to one another.
The pneumatic cutting device of any one of claims from 1 to 2, wherein at least one between the first discharge conduit (92) and the second discharge conduit (94) has a transversal section that is greater than and as a maximum up to five times the transversal section of the main conduit (81), in particular a transversal section between two and four times the transversal section of the main conduit (81), and more in particular a transversal section between two and three times the transversal section of the main conduit (81).
The pneumatic cutting device of the preceding claim, wherein both the first discharge conduit (92) and the second discharge conduit (94) have a transversal section that is greater than and maximum up to five times the transversal section of the main conduit (81), in particular a transversal section between two and four times the transversal section of the main conduit (81), and more in particular a transversal section between two and three times the transversal section of the main conduit (81).
The pneumatic cutting device of the preceding claim, wherein the first discharge conduit (92) and the second discharge conduit (94) have transversal sections that are substantially identical to one another.