Spray gumming unit

Abstract

 A spray gumming unit (1) wherein a conduit (5) for supplying gum (4) to a spray nozzle (2) has an intermediate portion (12) defined by two channels (10, 11) extending through a distributor (6) having two valve bodies (15, 16), each of which is movable, crosswise to the two channels (10, 11), between a first position wherein the valve body (15, 16) cuts off a first (10) of the two channels (10, 11) and leaves a second (11) of the two channels (10, 11) open, and a second position wherein the valve body (15, 16) cuts off the second channel (11) and leaves the first channel (10) open.

Description

[0001] The present invention relates to a spray gumming unit.

[0002] In particular, the present invention relates to a spray gumming unit especially suitable for use on a cigarette packing machine - to which the following description refers purely by way of example - for gumming sheets of packing material used on the packing machine.

[0003] Known cigarette packing machines normally comprise at least one spray gumming unit having one or more gum spray nozzles, each of which is supplied with gum by a respective supply conduit controlled by a valve comprising a valve body movable back and forth in a control direction between an open and a closed position. In various known embodiments, the valve body may be, for example, a pin movable axially along the conduit, or a shutter movable crosswise to the conduit.

[0004] On known packing machines, the above gumming units are normally used to deposit a succession of gum spots on blanks fed continuously past the nozzles. And to deposit each gum spot, the respective nozzle must be opened for a very short length of time, and the respective valve body moved fairly rapidly back and forth in said control direction between the open and closed position.

[0005] Though perfectly effective, valves of the above type fail to meet the extremely high operating speeds demanded on modern cigarette packing machines (capable of producing over 600 packets a minute) on account of the valve body, when depositing each gum spot, moving back and forth along the same path (in a first direction from the closed to the open position, and in the opposite direction from the open to the closed position). Which back and forth movement cannot be achieved rapidly on account of the mechanical inertia involved.

[0006] It is an object of the present invention to provide a spray gumming unit designed to eliminate the aforementioned drawbacks, and which at the same time is cheap and easy to produce.

[0007] According to the present invention, there is provided a spray gumming unit comprising a spray nozzle; a conduit for supplying gum to said spray nozzle; and valve means along said conduit and for controlling the conduit itself; characterized in that said valve means comprise two channels defining an intermediate portion of said conduit; two guides extending crosswise to said channels; two valve bodies, each movable along a respective said guide; and actuating means for moving each said valve body, along the respective said guide, between a first position wherein the valve body cuts off a first of said two channels and leaves a second of said two channels open, and a second position wherein the valve body cuts off said second channel and leaves said first channel open.

[0008] A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which:

Figure 1 shows a schematic partial section, with parts removed for clarity and parts in block form, of a preferred embodiment of the gumming unit according to the present invention;

Figure 2 shows a detail of Figure 1 in various operating positions.

[0009] Number 1 in Figure 1 indicates as a whole a spray gumming unit comprising a spray nozzle 2 connected to a supply device 3 for feeding gum 4 along a conduit 5 controlled by valve device defined by a distributor 6 on conduit 5.

[0010] Supply device 3 comprises a tank 7 containing gum 4, and from which a pump 8 feeds gum 4 to conduit 5 at a constant pressure regulated by a control unit 9.

[0011] Distributor 6 comprises two parallel channels 10 and 11 defining an intermediate portion 12 of conduit 5, and through which extend transversely two guide conduits 13 and 14 engaged by respective valve bodies 15 and 16, each of which is moved along respective conduit 13, 14 by an actuating device 17 and in opposition to a respective spring 18. Actuating device 17 comprises two known electromechanical actuators 19 and 20 associated respectively with bodies 15 and 16, and is controlled by control unit 9.

[0012] Each body 15, 16 is moved by actuating device 17 between a first position wherein body 15, 16 cuts off a first channel 10, 11 and leaves a second channel 11, 10 open, and a second position wherein body 15, 16 cuts off said second channel 11, 10 and leaves said first channel 10, 11 open.

[0013] Each body 15, 16 comprises an element 21 sliding in fluidtight manner along respective conduit 13, 14, and in which are defined two annular grooves 22 separated by a distance other (in particular, as shown in the Figure 1 embodiment, smaller) than the distance between channels 10 and 11.

[0014] As shown in Figure 2, for each body 15, 16 in said open position, a first of the two grooves 22 communicates with a first channel 10, 11, and a second channel 11, 10 is cut off by element 21; and in said second position, a second of the two grooves 22 communicates with said second channel 11, 10, and said first channel 10, 11 is cut off by element 21.

[0015] As shown in Figure 2, distributor 6 may assume an enabling position (as shown for example in Figures 1 and 2b) in which bodies 15 and 16 are so positioned as to leave channel 10 or 11 open; or a disabling position (as shown for example in Figures 2a and 2c) in which bodies 15 and 16 are so positioned as to each close a respective channel 10, 11 and so prevent supply of gum 4 from supply device 3 to nozzle 2, which is thus deactivated.

[0016] In the Figure 1 embodiment, a nonreturn valve 24 is provided along each channel 10, 11, close to nozzle 2.

[0017] Operation of unit 1 will now be described with particular reference to Figure 2.

[0018] To deposit a gum spot on a blank 23 fed continuously past nozzle 2, nozzle 2 must be activated, i.e. connected hydraulically to supply device 3, for a very short length of time.

[0019] Distributor 6 is normally set to said disabling position - as shown for example in Figure 2a - in which valve body 15 is in said first position cutting off channel 10 and leaving channel 11 open, and valve body 16 is in said second position cutting off channel 11 and leaving channel 10 open. That is, with bodies 15 and 16 positioned as described above, both channels 10 and 11 are closed.

[0020] To deposit a gum spot on blank 23, control unit 9 commands actuating device 17 to move body 16 from said second position to said first position, in which both bodies 15, 16 leave channel 11 open (Figure 2b) and close channel 10, thus enabling gum 4 to flow along channel 11 to nozzle 2. Supply of gum 4 to nozzle 2 is cut off, not by moving body 16 back to its original position cutting off channel 11, but by moving body 15 from its original position cutting off channel 10, i.e. from the first position to the second position cutting off channel 11. Supply of gum 4 to nozzle 2 is therefore cut off by body 16 being maintained (Figure 2c) in the first position cutting off channel 10.

[0021] In the course of each gumming cycle, therefore, the time interval between activation and deactivation of nozzle 2 is extremely short, by nozzle 2 being activated and deactivated by two distinct mechanical members (bodies 15 and 16), each of which performs one stroke in one direction, thus considerably reducing the mechanical inertia involved.

Claims

1. A spray gumming unit comprising a spray nozzle (2); a conduit (5) for supplying gum (4) to said spray nozzle (2); and valve means (6) along said conduit (5) and for controlling the conduit (5) itself; characterized in that said valve means (6) comprise two channels (10, 11) defining an intermediate portion (12) of said conduit (5); two guides (13, 14) extending crosswise to said channels (10, 11); two valve bodies (15, 16), each movable along a respective said guide (13, 14); and actuating means (17) for moving each said valve body (15, 16), along the respective said guide (13, 14), between a first position wherein the valve body (15, 16) cuts off a first (10) of said two channels (10, 11) and leaves a second (11) of said two channels (10, 11) open, and a second position wherein the valve body (15, 16) cuts off said second channel (11) and leaves said first channel (10) open.

2. A unit as claimed in Claim 1, characterized in that each said valve body (15, 16) comprises an element (21) sliding in fluidtight manner along the respective said guide (13, 14), and in which are defined two passages (22) separated by a distance other than the distance between the two channels (10, 11).

3. A unit as claimed in Claim 1 or 2, characterized in that said actuating means (17) are electromechanical actuating means.

4. A unit as claimed in any one of Claims 1 to 3, characterized by comprising a control unit (9) for commanding said actuating means (17) to move a first (15) of said two valve bodies (15, 16) from said first position to said second position to feed gum (4) to said spray nozzle (2), and to subsequently move a second (16) of said two valve bodies (15, 16) from said second position to said first position to cut off supply of gum (4) to said spray nozzle (2).

Drawing