VALVE ASSEMBLY FOR BLOWING OR DRAW-BLOWING BOTTLES MADE OF POLYMER MATERIAL

Abstract

The present invention relates to a valve assembly for blowing or draw-blowing preforms made of polymer material, applicable to a machine suitable to transform said preforms into bottles or containers.

In particular, the invention relates to a valve assembly (1) comprising a control block (2) and a blowing block (3), in which the blowing block (3) comprises an outer body (50) having a longitudinal axis, inside which a blowing cylinder ending at the bottom with a nozzle (58) suitable to be coupled with the neck of a container (C), is slidingly accommodated, and wherein the control block (2) receives pressurized air from at least one pressurized air source and sends it to said blowing block (3) according to a predetermined pressure profile dependent on the selected blowing cycle, in which the control block (2) comprises a plurality of valves for dispensing pressurized air at different pressures, and an air exhaust valve, characterized in that said valves are driven by pressurized air at a pressure between 15 and 40 bar.

Claims

1. A valve assembly (1) comprising a control block (2) and a blowing block (3), wherein the blowing block (3) comprises an outer body (50) having a longitudinal axis (D), inside which a blowing cylinder (51) ending at the bottom with a nozzle (58) suitable to be coupled with the neck of a container (C), is slidingly accommodated, and wherein the control block (2) receives pressurized air from at least one pressurized air source and sends it to said blowing block (3) according to a predetermined pressure profile dependent on the selected blowing cycle, wherein the control block (2) comprises a plurality of valves (11a, 11b, 11c) for dispensing pressurized air at different pressures, and an air exhaust valve (39), characterized in that said valves (11a, 11b, 11c, 39) are driven by pressurized air at a pressure (P2) between 15 and 40 bar.

2. The valve assembly (1) according to claim 1, wherein the control block (2) comprises a first conduit (12a) for pressurized air at a first pressure (P1), a second conduit (12b) for pressurized air at a second pressure (P2) which is greater than the first pressure (P1), and a third conduit (12c) for pressurized recovery air at a third pressure (Px) which varies in the range which is greater than or equal to said first pressure (P1) and less than or equal to said second pressure (P2), wherein said first, second and third conduits (12a, 12b, 12c) are intercepted by a first, second and third dispensing valve (11a, 11b, 11c) of pressurized air, respectively, at said first, second and third pressure (P1, P2, Px), and wherein said dispensing valves (11a, 11b, 11c) are connected to a transverse conduit (21) which in turn comprises a connection opening (22) to the blowing block (3).

3. The valve assembly (1) according to claim 2, wherein said first, second and third dispensing valves (11a, 11b, 11c) and said exhaust valve (39) are placed perpendicularly to said first, second and third pressurized air inlet conduits (12a, 12b, 12c), respectively, and to said transverse conduit (21), and wherein each of said dispensing (11a, 11b, 11c) and exhaust (39) valves comprises: an H-shaped piston (17) comprising a stem (19′″), a first head (19′), and a second head (19″), wherein said heads (19′, 19″) have a greater diameter than the stem (19′″); a complementary seat (20) in which the piston (17) slides, said complementary seat (20) having a middle portion (20′″), a first expansion chamber (20′) at the first head (19′) of the piston (17) and a second expansion chamber (20″) at the second head (19″) of the piston (17), in which: i) both the first head (19′) and the second head (19″) comprise respective outer surfaces (25′, 25″) and respective shoulders (24′, 24″), the shoulders (24′, 24″) being configured to be coupled with the respective abutment surfaces (23′, 23″) of said expansion chambers (20′, 20″), ii) a gap (26) is arranged between the middle portion (20′″) of the seat (20) and the stem (19′″) of the piston (17), in the section connecting the first expansion chamber (20′) to the transverse conduit (21), iii) the outer surface (25′) of the first head (19′) of the pistons (17) is star-shaped and comprises a plurality of chamfers (28) which create micro channels along a side surface (29) of the first head (19′), said micro channels being configured to allow the passage of pressurized air through the gap (26).

4. The valve assembly (1) according to claim 2, wherein a first branch conduit (16), which is T-shaped and comprises a first portion (16′) perpendicular to the second conduit (12b) and a second portion (16″) which extends along a transverse direction with respect to said first, second and third conduits (12a, 12b, 12c) and which lies on a plane parallel to the plane on which the axes (A, B, C) of said first, second and third conduits (12a, 12b, 12c) lie, starts from the second conduit (12b) for the pressurized air at the second pressure (P2), and wherein the following starts from said second portion (16″) of the first branch conduit (16): a second branch conduit (37a) which extends perpendicularly to the plane in which the first branch conduit (16) lies; a first driving channel (30c) intercepted by a first solenoid control valve (32c); a second driving channel (33) intercepted by a second solenoid control valve (34), and wherein a third branch conduit (37b) which extends on a plane parallel to the first branch conduit (16) starts from the second branch conduit (37a), wherein a third and fourth driving channels (30a, 30b) intercepted by a third and fourth solenoid control valve (32a, 32b), respectively, perpendicularly start from said third branch conduit (37b) in the same plane parallel to the first branch conduit (16).

5. The valve assembly (1) according to claim 4, wherein the first, third and fourth solenoid control valves (32c, 32a, 32b) drive the third, first and second dispensing valves (11c, 11a, 11b), respectively, by means of respective outlet channels (31a, 31b, 31c) which start from said solenoid control valves (32a, 32b, 32c) and which lead into the upper part of the second expansion chamber (20″) of the respective dispensing valves (11a, 11b, 11c).

6. The valve assembly (1) according to claim 4, wherein the second driving channel (33) intercepted by the second solenoid control valve (34) is connected downstream of the latter to a counter-pressure chamber (102) of a mold (100).

7. The valve assembly (1) according to claim 3, wherein the exhaust valve (39) is connected downstream to an air exhaust device (42) and wherein a fifth driving channel (38) of said air exhaust valve (39) starts from the second conduit (12b) of pressurized air at said second pressure (P2), wherein said exhaust valve (39) is mounted in reverse position with respect to the dispensing valves (11a, 11b, 11c) so that the outer surface (25′) of the first head (19′) faces upwards, wherein the fifth channel (38) is intercepted by a respective solenoid control valve (40) and continues downstream of said solenoid valve (40) in an outlet channel (41) which leads into the second expansion chamber (20″) of the seat (20), in intermediate position between said abutment surface (23″) and said shoulder (24″).

8. The valve assembly (1) according to claim 4, wherein the outer body (50) of the blowing block (3) comprises an opening (52) which is put into flow connection with the opening (22) of the control block (2) from which the pressurized air is dispensed, an inner surface (50′) of the outer body (50) further comprising an upper recess (53) and a lower recess (54) so as to form an upper annular chamber (55) and a lower annular chamber (56) with an outer surface (51′) of the blowing cylinder (51), and wherein the blowing cylinder (51) is hollow and comprises a longitudinal channel (57) which opens outwards at the nozzle (58), there being arranged, between an inner surface (51″) and the outer surface (51′) of the blowing cylinder (51), a plurality of radial channels (59) which connect the outside of the blowing cylinder (51) with the longitudinal channel (57) and which extend along a downwards tilting direction from the outer surface (51′) to the inner surface (51″), and wherein said second branch conduit (37a) of the control block (2) is connected to a conduit (37c) of the blowing block (3), which in turn is connected to two solenoid control valves (60′, 60″) of the blowing block (3), which are configured to send pressurized air at said second pressure (P2) alternately to the upper annular chamber (55) or to the lower annular chamber (56), so that when the pressurized air is introduced into the upper annular chamber (55), the blowing cylinder (51) slides downwards up to engaging the neck of a preform, and simultaneously the opening (52) of the outer body (50) from which the pressurized air is introduced aligns with the radial channels (59) of the blowing cylinder (51); when instead the pressurized air is introduced into the lower annular chamber (56), the blowing cylinder (51) slides upwards so as to disengage from the neck of the container and discontinue the blowing air flow.

9. The valve assembly (1) according to claim 2, wherein said first and second conduits (12a, 12b) are pneumatically connected to a pressurized air manifold (8) comprising a first chamber (9a) for supplying pressurized air at said first pressure (P1) and a second chamber (9b) for supplying pressurized air at said second pressure (P2), and wherein said third conduit (12c) is connected to a storage tank (10) of pressurized air at said third pressure (Px).

10. The valve assembly (1) according to claim 2, wherein the first conduit (12a) is intercepted by a flow regulator (13) of said pressurized air at said first pressure (P1).

11. The valve assembly (1) according to claim 2, wherein said first and second conduits (12a, 12b) are intercepted upstream of said dispensing valves (11a, 11b) by respective unidirectional valves (14, 15) configured to prevent the pressurized air at said first and second pressures (P1, P2) from returning towards the manifold (8).

12. A machine for blowing or draw-blowing containers, comprising a plurality of molds (100), a valve assembly (1) according to claim 1 being mounted on each mold (100), said machine comprising at least one pressurized air manifold (8) comprising a first chamber (9a) for supplying pressurized air at said first pressure (P1) and a second chamber (9b) for supplying pressurized air at said second pressure (P2), and at least one storage tank (10) of pressurized air at said third pressure (Px).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 shows a partial exploded perspective view of the valve assembly according to the invention;

[0037] FIG. 2 shows a partial transparency view of the valve assembly according to the invention;

[0038] FIG. 3 shows a top view of the valve assembly in FIG. 1, according to a cross section;

[0039] FIG. 4A shows a view according to section IVa in FIG. 2;

[0040] FIG. 4B shows a view according to section IVb in FIG. 2;

[0041] FIG. 4C shows a view according to section IVc in FIG. 2;

[0042] FIG. 5 shows a view according to section V-V in FIG. 2;

[0043] FIG. 6A shows a partial transparency perspective view of the blowing block in FIG. 1;

[0044] FIG. 6B shows a side sectional view of the blowing block in FIG. 6A;

[0045] FIG. 7A shows a sectional view according to direction VII-VII in FIG. 2, of a first operating condition;

[0046] FIG. 7B shows the view in FIG. 7A, in a second operating condition;

[0047] FIG. 7C shows the view in FIG. 7A, in a third operating condition;

[0048] FIG. 7D shows the view in FIG. 7A, in a fourth operating condition;

[0049] FIG. 8 shows a sectional view of a detail in FIG. 7A;

[0050] FIG. 9 shows a perspective view of the assembly, comprising the mold, valve assembly and pressurized air manifold;

[0051] FIG. 10 shows a perspective view of the mold alone;

[0052] FIG. 11 shows a perspective view of a half-mold, showing the inner face thereof;

[0053] FIG. 12 shows a longitudinal sectional view of a detail of a half-mold.

DETAILED DESCRIPTION OF THE INVENTION

[0054] FIG. 1 shows, in its entirety, the valve assembly, indicated by numeral 1, comprising a control block 2 and a blowing block 3, which are shown in disassembled condition, while FIG. 2 shows the valve assembly 1 in assembled condition.

[0055] The control block 2 serves the function of receiving pressurized air from one or more pressurized air sources, and sending said pressurized air to the blowing block 3 with a predetermined pressure profile.

[0056] The blowing block 3 receives said pressurized air with said predetermined pressure profile from the control block 2 and introduces said pressurized air into a heated preform inside a mold 100 for forming a container by means of blowing or draw-blowing.

[0057] The predetermined pressure profile may vary according to the container to be made, and generally comprises: [0058] a first step, or pre-blowing step, at a first pressure P1; [0059] a second step, or blowing step, at a second pressure P2 which is greater than or equal to P1; [0060] a third step, or exhausting step of the overpressure.

[0061] The first pressure P1 generally is between 4 and 15 bar, while the second pressure P2 generally is between 15 and 40 bar.

[0062] FIGS. 3 to 5 show the control block 2 in detail.

[0063] The control block 2 comprises a body 4 in which the passages for the pressurized air are obtained. Body 4 comprises a first inlet opening 5a of pressurized air, a second inlet opening 5b of pressurized air and a third inlet-outlet opening 5c of pressurized air, which in the embodiment in the drawings, is placed between the first and the second inlet openings 5a, 5b.

[0064] The openings 5a, 5b, 5c comprise respective sleeves 6a, 6b, 6c for the connection with the pipes for the passage of pressurized air. In particular, with reference to FIG. 9, the sleeves 6a, 6b, 6c are connected to respective first, second and third pipes 7a, 7b, 7c, which in turn are connected to a system 101 for supplying pressurized air comprising a pressurized air manifold 8, having a first chamber 9a for supplying air at said first pressure P1 and a second chamber 9b for supplying air at said second pressure P2, and a storage tank 10.

[0065] More specifically: [0066] the first pipe 7a connects said first inlet opening 5a with said first supply chamber 9a; [0067] the second pipe 7b connects said second inlet opening 5b with said second supply chamber 9b; [0068] the third pipe 7c connects said third inlet-outlet opening 5c with the storage tank 10 for storing pressurized air at a pressure Px between P1 and P2.

[0069] The pressurized air manifold 8 in turn is connected to one or more pressurized air sources (not shown).

[0070] The storage tank 10 is toroidal-shaped in the embodiment in the drawings and encloses manifold 8 within its circumference, but it could have a different shape and position in other embodiments.

[0071] Returning to the description of the control block 2, the first inlet opening 5a of pressurized air, dedicated to the pre-blowing step, preferably has a smaller gap than the second and third openings 5b, 5c.

[0072] The first inlet opening 5a is connected downstream to a first dispensing valve 11a of pressurized air at said first pressure P1 by means of a first conduit 12a in body 4. Conduit 12a is intercepted by a flow regulator 13 and a unidirectional valve 14, which prevents the pressurized air dispensed with said pressure P1 from returning towards the inlet opening 5a.

[0073] The flow regulator 13 comprises a body 13′ ending with a threaded portion 13″ at the inner end thereof, said threaded portion 13″ being coupled to a complementary threaded seat obtained in body 4 of the control block 2. Body 13′ of the flow regulator 13 has a hole or groove 13′″ which allows regulating the gap for the passage of pressurized air in conduit 12a by means of screwing or unscrewing body 13″. Thereby, the correct flow of pressurized air for the pre-blowing, which depends on the features of the container to be made, may be prepared at the beginning of the blowing or draw-blowing procedure.

[0074] The second inlet opening 5b is connected downstream to a second dispensing valve 11b of pressurized air at said second pressure P2 by means of a second conduit 12b in body 4. Conduit 12b also is intercepted by a unidirectional valve 15, which prevents the pressurized air dispensed with said pressure P2 from returning towards the inlet opening 5b.

[0075] The third inlet opening 5c is connected downstream to a third dispensing valve 11c of pressurized air at said third pressure Px by means of a third conduit 12c in body 4. Conduit 12c is not intercepted by a unidirectional valve because the pressurized air must circulate in both directions, as indicated by the double arrow in FIG. 3.

[0076] As shown, for example, in FIG. 7A, the dispensing valves 11a, 11b, 11c are connected to a transverse conduit 21 which in turn comprises an opening 22 (also shown in FIG. 1) which extends perpendicularly so as to connect to the blowing block 3, as described below, so as to provide it with the pressurized air for the container blowing operations.

[0077] As shown in FIGS. 7A-7D, the dispensing valves 11a, 11b, 11c are placed perpendicularly with respect to the pressurized air inlet conduits 12a, 12b, 12c. More specifically, with reference to FIG. 8, each of said dispensing valves 11a, 11b, 11c comprises an H-shaped piston 17 comprising a stem 19′″, a first head 19′, and a second head 19″, in which said heads 19′, 19″ have a greater diameter than stem 19′″. Piston 17 slides in a complementary seat 20 which has a middle portion 20″′, a first expansion chamber 20′ at the first head 19′ of piston 17 and a second expansion chamber 20″ at the second head 19″ of piston 17. Therefore, the middle portion 20′″ of seat 20 has a smaller diameter than the expansion chambers 20′, 20″ and substantially corresponding to the one of the stem 19′″ of piston 17. However, a gap 26 is arranged between the middle portion 20′″ of seat 20 and the stem 19′″ of piston 17, in the section connecting the first expansion chamber 20′ to the transverse conduit 21.

[0078] Both the first head 19′ and the second head 19″ comprise respective outer surfaces 25′, 25″ and respective shoulders 24′, 24″. The shoulders 24′, 24″ are configured to be coupled with respective abutment surfaces 23′, 23″ of said expansion chambers 20′, 20″.

[0079] Stem 19′″ and the second head 19″ of piston 17 further comprise gaskets 27, for example, O-rings, for sealing the pressurized air.

[0080] As better shown in FIG. 3, the outer surface 25′ of the first head 19′ of the pistons 17 is star-shaped and comprises a plurality of chamfers 28 which create micro channels along the side surface 29 of the first head 19′ and allow the passage of the pressurized air.

[0081] When, as shown, for example, in FIG. 8, shoulder 24′ of the first head 19′ abuts against the respective abutment surface 23′ of seat 20, the pressurized air originating from the conduits 12a, 12b, 12c cannot pass, whereby the dispensing valve 11a, 11b, 11c is in closing condition. If, vice versa, such as, for example, shown in FIG. 7A relatively to the first valve 11a, it is the second head 19″ to abut against the respective abutment surface 23″ of seat 20, the pressurized air dispensed through conduit 12a can pass through the micro channels of the side surface 29 of the first head 19′ and cross gap 26 so as to reach the transverse conduit 21, and by means thereof, the connection opening 22 with the blowing block.

[0082] With reference now to FIGS. 4A-4C and 5, a first branch conduit 16, which is T-shaped and comprises a first portion 16′ perpendicular to the second conduit 12b and a second portion 16″ which extends along a transverse direction with respect to said first, second and third conduits 12a, 12b, 12c and which lies on a plane parallel to the plane on which the axes A, B, C of said first, second and third conduits 12a, 12b, 12c lie, starts from the second conduit 12b for the pressurized air at the second pressure P2.

[0083] The following start from the second portion 16″ of the first branch conduit 16: [0084] a second branch conduit 37a which extends perpendicularly to the plane in which the first conduit 16 lies; [0085] a first driving channel 30c intercepted by a first solenoid control valve 32c; [0086] a second driving channel 33 intercepted by a second solenoid control valve 34.

[0087] With reference to FIG. 4B, a third branch conduit 37b which extends on a plane parallel to the first branch conduit 16 starts from the second branch conduit 37a. A third and fourth driving channel 30a, 30b intercepted by a third and fourth solenoid control valve 32a, 32b, respectively, perpendicularly start from said third branch conduit 37b in the same plane parallel to the first branch conduit 16.

[0088] The first, third and fourth solenoid control valves 32c, 32a, 32b drive the third, first and second dispensing valves 11c, 11a, 11b, respectively. In this regard, said solenoid control valves 32a, 32b, 32c start from respective outlet channels 31a, 31b, 31c which lead into the upper part of the second expansion chamber 20″ of the respective dispensing valves 11a, 11b, 11c, that is into the upper chambers shown in FIGS. 7A-7D, so as to drive the opening of the dispensing valves 11a, 11b, 11c, as described below.

[0089] The second driving channel 33 intercepted by the second solenoid control valve 34 is connected downstream of the latter to a counter-pressure chamber 102, shown in FIGS. 10-12 and described below.

[0090] As shown in FIGS. 4C and 5, a fifth driving channel 38 of a pressurized air exhaust valve 39 starts from the second conduit 12b of pressurized air at said second pressure P2.

[0091] The exhaust valve 39, shown in FIGS. 7A-7D, is entirely similar to the dispensing valves 11a, 11b, 11c, but it is mounted in reverse position so that the outer surface 25′ of the first head 19′ faces upwards.

[0092] The fifth driving channel 38 is intercepted by a respective solenoid control valve 40 and continues downstream of said solenoid valve 40 in an outlet channel 41 (FIG. 5) which leads into the second expansion chamber 20″ of seat 20, in intermediate position between abutment surface 23″ and shoulder 24″.

[0093] The exhaust valve 39 is connected downstream to an air exhaust device 42.

[0094] The blowing block 3, shown in FIGS. 6A-6B, comprises an outer body 50 having a longitudinal axis D, inside which a blowing cylinder 51 is slidingly accommodated.

[0095] The outer body 50 comprises an opening 52 which, when the valve assembly 1 is assembled, is put into flow connection with opening 22 of the control block 2 from which the pressurized air is dispensed. The inner surface 50′ of the outer body 50 further comprises an upper recess 53 and a lower recess 54 so as to form, with the outer surface 51′ of the blowing cylinder 51, an upper annular chamber 55 and a lower annular chamber 56 which are kept airtight at the passage of air by virtue of appropriate gaskets 60, such as, for example, O-rings.

[0096] The blowing cylinder 51 slides along axis D and at the bottom comprises a nozzle 58 suitable to engage with the neck of a container C (shown with a dashed line in FIGS. 6A and 6B). The blowing cylinder 51 is hollow, comprising a longitudinal channel 57 which opens outwards at nozzle 58. A plurality of radial channels 59 is arranged between the inner surface 51″ and the outer surface 51′ of the blowing cylinder 51. The radial channels 59 connect the outside of the blowing cylinder 51 with the longitudinal channel 57 and extend along a downwards tilting direction from the outer surface 51′ to the inner surface 51″.

[0097] The second branch conduit 37a of the control block 2 described above is connected to a conduit 37c of the blowing block 3, which in turn is connected to two solenoid control valves 60′, 60″ of the blowing block 3, which control the sending of the pressurized air at said second pressure P2 alternately to the upper annular chamber 55 or to the lower annular chamber 56 of the blowing block 3. When the pressurized air is introduced into the upper annular chamber 55, the blowing cylinder 51 slides downwards so as to engage the neck C of the preform. Simultaneously, opening 52 of the outer body 50 from which pressurized air is introduced aligns with the radial channels 59 of the blowing cylinder 51, thus allowing the container to be blown. When instead the pressurized air is introduced into the lower annular chamber 56, the blowing cylinder 51 slides upwards so as to disengage from neck C of the container and discontinue the blowing air flow.

[0098] With reference to FIGS. 10-12, they show a mold 100 for blowing or draw-blowing preforms for making containers. Mold 100 comprises two half-molds 100′, 100″ which may take on a closed position (shown in FIG. 10) and an open position for controlled rotation around a hinge axis 103.

[0099] Each half-mold 100′, 100″ comprises a mold-support 104 and a mold element 105, which outer surface 105′, together with the outer surface 105′ of the other half-mold, forms the forming cavity of the container. A gap constituting the counter-pressure chamber 102 is arranged between mold-support 104 and mold element 105. Said counter-pressure chamber 102 is connected by means of the openings 106, 106′ and suitable pipes to the fourth channel 33 of the control block 2 so that the pressurized air passing through such a conduit imparts a sufficient counter-pressure on the mold element 105 as to counteract the blowing pressure, and thus avoid the partial opening of mold 100.

[0100] FIGS. 7A-7D show the various operating steps of the blowing performed by means of the valve assembly 1 of the invention.

[0101] The dispensing valves 11a, 11b, 11c and the exhaust valve 39 are in closing condition when the pressurized air originating from the first, second and third conduits 12a, 12b, 12c is introduced into the respective first expansion chambers 20′ and when the pressurized air originating from the sixth channel 38, and therefore from the outlet channel 41, is introduced into the second expansion chamber 20″. Vice versa, the dispensing valves 11a, 11b, 11c are in opening condition when the pressurized air is introduced into the respective second expansion chambers 20″ through the outlet channels 31a, 31b, 31c. Similarly, the exhaust valve 39 is in opening condition when the introduction of pressurized air into the second expansion chamber 20″ is discontinued and therefore when the pressurized air originating from the transverse conduit 21 passes through the grooves of the first head 19′ and from there, into the first expansion chamber 19′.

[0102] FIG. 7A shows the condition in which only the first dispensing valve 11a is open, whereby pressurized air at pressure P1 is introduced into the blowing block 3 for pre-blowing the preform.

[0103] FIG. 7B shows the condition in which only the second dispensing valve 11b is open, whereby pressurized air at pressure P2 is introduced into the blowing block 3 for blowing the preform.

[0104] FIG. 7C shows the condition in which only the third dispensing valve 11c is open, whereby pressurized air at pressure Px is introduced into or drawn from the blowing block 3 as recovery pressure. Pressure Px therefore varies between a minimum pressure, for example about 4 bar, and a maximum pressure, for example, about 40 bar. At the beginning of the blowing, the excess pressurized air at pressure P1 or P2 is recovered in tank 10 through the third valve 11c, then when the pressure in tank 10 is greater than the pressure dispensed, typically during the pre-blowing, the pressurized air originating from tank 10 is reutilized for the blowing.

[0105] FIG. 7D instead shows the condition in which only the exhaust valve 39 is open.

[0106] The operating sequence of the valves 11a, 11b, 11c, 39, implemented by means of the respective solenoid control valves 32a, 32b, 32c, 40 controlled by a control unit, can be programmed and is determined by the type of blowing cycle required.

[0107] One advantage of the valve assembly 1 of the invention with respect to the known devices is that the branch from conduit 12b of pressurized air at a high pressure (pressure P2) is used without any reduction in pressure for driving all the dispensing 11a, 11b, 11c and exhaust 39 valves. This allows having increased thrust on the pistons 17, which therefore may have a thrust surface 25′, 25″ with a smaller width. Therefore, there will be a smaller air volume, a reduced dead volume of air in the valve, reduced dimensions of the valves themselves, and increased reactivity of the valve following the implementation of the solenoid valves.

[0108] Another advantage lies in the fact that the same pressurized air at pressure P2 is directly sent to the counter-pressure chamber 102, with the sole interposition of the solenoid control valve 34.

[0109] It is apparent that only some particular embodiments of the present invention have been described, to which those skilled in the art will be able to make all changes required to adapt it to particular applications, without departing from the scope of protection of the present invention.