GB2047165A - Printing machines - Google Patents

Abstract

A printing machine for printing on individual articles such as plastics bags has a rotatable printing roller 1 to which articles are fed one at a time. Rotation of the roller 1 is automatically initiated when an article approaches the roller, as detected by a sensor 27, and the roller 1 stops after it has rotated through a predetermined angle. Feed rollers 7, 16 and 19 may be continuously driven. The printing roller 1 may stop after a single revolution, either as a result of a projection, preferably adjustable, on the roller 1 cooperating with a switch, or by a timer in the control circuitry. <IMAGE>

Description

SPECIFICATION Printing machines This invention relates to printing machines, particu larly although not exclusively for printing on individual flexible sheet-like articles, such as plastics carrier bags, in relatively small runs.

A known printing machine for printing on plastics carrier bags has a continuously rotating printing roller into contact with which the bags are fed one at a time by a person operating the machine. With this machine, however, the problem arises that a bag may adhere to the surface of the roller and may be drawn around with same, before the operator can free the bag, to a position at which it fouls an inking mechanism for the roller or otherwise adversely affects normal operation of the machine.

An object of the present invention is to provide a printing machine with which such disruption of machine operation can be avoided or at least appreciably reduced.

According to the invention therefore there is provided a printing machine, for printing on individual articles, having a rotatable printing roller into contact with which said articles can be fed, and a drive means for rotatably driving said roller, characterised in that a control circuit is provided for controlling operation of the said drive means such that, in use, subsequent to actuation of the control circuit, the roller is caused to rotate through a predetermined angle and is then brought to rest, and sensing means is provided which responds to the presence of one said article at a predetermined position in the path of feed of the articles to the roller to effect said actuation of the control circuit.

With this arrangement it will be appreciated that the roller does not rotate continuously in use but instead rotates on an intermittent basis as successive articles are fed thereto. Accordingly, in the event that an article adheres to the roller, the operator need only withhold feeding of the next article in order to ensure that the roller stops to enable him to free the adhered article, and by appropriate selection of the said predetermined angle of rotation of the roller in relation to the position of an inking mechanism therefor and in relation to the size of the article and the position of introduction of same to the roller, it can be ensured that the roller will stop before the article can reach and appreciably foul the inking mechanism.Thus, and in accordance with a particularly preferred embodiment, the roller may be arranged to rotate through one complete revolution and the article may be introduced to the roller immediately after an inking mechanism therefor. It is however to be understood that the invention is not intended to be restricted to this arrangement and if desired, the roller may rotate through more than one revolution, for example for the purpose of effecting multiple printing of each article, and whilst with this arrangement it may not be possibie to prevent fouling of an inking mechanism by an adhered article, the extent of such fouling may be of a limited nature.

With regard to the said sensor, in a particularly preferred embodiment, this comprises an infra-red transmitting device in conjunction with an infra-red receiving element. Such device and element may be arranged on opposite sides of the path of article feed such that infra-red radiation normally passes from the transmitting device to the receiving element but is interrupted by the passage of an article therebetween; or, alternatively, the device and element may be arranged on the same side of such path so that radiation is only transmitted from the transmitting device to the receiving element when an article is in a position to act as a reflector for such radiation. An infra-red sensor is particularly preferred because it can be utilised with transparent articles, such as transparent polyethylene plastics bags.However, if desired other forms of sensors may be used which reiy on interruption or reflection of any suitable form of radiation, or which involve modification of the properties of a device (such as modification of capacitance of an electronic circuit element), or which involve mechanical operation of a device, or which rely on any other principle of operation in response to the presence of an article in predetermined positional relationship with regard to the sensor.

After rotation of the roller through the said predetermined angle, stopping of same may be effected as a consequence of mechanical operation of a limit switch by an operating member connected to the roller. In this case, the operating member may be positionally adjustable so that the starting and stopping positions of the roller, and consequently the positioning of the printed matter applied to the articles, can be adjusted. Alternatively, if desired, a timer of adjustable duration or other suitable circuit may be incorporated in the control circuit so that the roller is brought to rest a predetermined period after commencement of rotation of same.

The invention will now be described further by way of example only and with reference to the accompanying drawings in which: Figure 1 is a diagrammatic perspective view of one form of a printing machine according to the invention; and Figure 2 is a diagrammatic representation of the control circuit of the invention.

The machine has a horizontally rotatably mounted printing roller 1 which defines a nip with a lower rotatable counter roller 2.

At an inlet side of the two rollers 1,2 and level with the nip between same there is a flat horizontal feed surface 3. A feed table having a flat horizontal surface 4 level with the surface 3 has a leading edge 5 which is spaced slightly from a trailing edge 6 of the surface 3 and a feed roller 7 is mounted between such edges 5,6 so that the upper extremity of the roller is between and level with the surfaces 3,4.

Three spaced rubber wheels are freely rotatably mounted at adjustable positions so as to press onto the roller 7. An upstanding guide wall 9 is adjustably mounted on the table surface 4.

Above the surface 3, at the inlet side of the rollers 1,2, there is provided an inking mechanism 10 comprising an elongate tray 11 and a pair of rollers 12, 13, such tray 11 and rollers 12, 13 extending longitudinally parallel to the axis of the roller 1 with one roller 12 in contact with or slightly spaced from the surface of the roller 1 slightly above the surface 3 and with the other roller 13 in contact with the first roller 12 and projecting into the tray 11. By appropriate rotation of the rollers 12, 13, ink in the tray 11 can be applied to the surface of the roller 1.

At an outlet side of the rollers 1,2 and level with the nip between same, there is a flat horizontal feed surface 14. A further feed surface 15 is level with the surface 14 and has a trailing edge which is spaced slightly from a leading edge of the surface 14. A feed roller 16 and an arrangement of wheels (not visible in the drawing) of like form to the roller 7 and wheels 8 are arranged between the two surfaces 14, 15.

The leading edge of the feed surface 15 is level with an inlet end of an endless conveyor 17 comprising a plurality of spaced apart bands 18 which run round circumferentially grooved rollers 19. The conveyor 18 runs through a drying tunnel 20 containing heating lamps.

The feed rollers 7, 16 and the conveyor rollers 19, are connected to a motor 21 via chain drives 22 so tha- they can be continuously driven by same (Figure 2). he rollers 1, 2, 12, 13 are connected to the motor 21 via an electromagnetic clutch/brake mechanism 23 so that they are driven when the clutch/brake mechanism 23 is operated but are stopped when such mechanism is not operated. The clutch/brake mechanism 23 is connected to a control circuit 24 which controls operation of same. The control circuit 24 is also connected to a sensor system which comprises an infra-red radiation transmitting device 25 and an infra-red sensitive receiving device 26.

These devices are arranged side-by-side beneath an aperture 27 in the surface 3 close to the nip between the rollers 1,2 and also close to the inking mechanism 10. The control circuit 24 is further connected to a microswitch 28 which is mounted alongside one end of the roller 1 and is arranged to be operated, in one rotational position of the roller 1, by an operating member 29 adjustably mounted on an adjacent end shaft 30 of the roller 1.

In use, plastics carrier bags can be fed, one at a time by hand, across the table surface 4 between the rotating feed roller 7 and the wheels 8, with the edges of the bags engaging the guide wall 9.

As the leading edge of a bag crosses the opening 27, infra-red radiation is reflected from the transmitting device 25 to the receiving device 26 by the underside of the bag. An impulse is thereby transmitted to the control circuit 24 which is triggered by such impulse and effects operation of the mechanism 23 so that the rollers 1,2, 12, 13 are set in rotation. The bag is drawn through the nip between the rollers 1,2 and printed matter is applied thereto by the roller 1. As the roller 1 completes a full revolution, the printed bag leaves the nip and the member 29 reaches a position at which it operates the microswitch 28.Such operation effects resetting of the control circuit 24 so that the mechanism 23 is no longer operated and the rollers 1,2,12,13 are brc ked to rest pending feed of a subsequent bag into sui erimposed relationship with the opening 27.

5 ts the printed bag leaves the nip it is advanced by the feed roller 16 (and associated wheels) onto the conveyor 17 and is then advanced through the drying tunnel 20. The use of spaced bands 18 ensures that there is no undue build-up of ink solvent vapour in the tunnel 20 which would prevent adequate drying.

The machine described above is particularly suitable for printing plastics carrier bags in relatively small runs. The bags are fed to the printing roller by an operator standing alongside the table and it will be appreciated that the printing can be effected in a carefully controlled manner, even by an unskilled operator, since the roller 1 is driven intermittently, not continuously, and is only set in rotation when a bag is fed by the operator to the roller 1. A particular advantage of this arrangement arises from the fact that the roller 1 stops after one revolution whereby, in the event that a bag adheres to the roller 1, and is drawn round with same, the roller 1 stops before the bag can foul the inking mechanism 10.

It is of course to be understood that the invention is not intended to be restricted to the details of the above embodiment which are described by way of example only. In particular it is to be understood that the invention is not intended to be restricted to the printing of plastics carrier bags but may be utilised in the context of printing any other suitable articles.

Claims (13)

1. A printing machine, for printing on individual articles, having a rotatable printing roller into contact with which said articles can be fed, and a drive means for rotatably driving said roller, characterised in that a control circuit is provided for controlling operation of the said drive means such that, in use, subsequent to actuation of the control circuit, the roller is caused to rotate through a predetermined angle and is then brought to rest, and sensing means is provided which responds to the presence of one said article at a predetermined position in the path of feed off the articles to the roller to effect said actuation of the control circuit.

2. A machine according to claim 1, wherein the roller iis arranged to rotate through one complete revolution before being brought to rest.

3. A machine according to claim 2, wherein the article is arranged to be introduced to the roller immediately after an inking mechanism therefor.

4. A machine according to any one of claims 1 to 3, wherein the said sensor comprises an infra-red transmitting device in conjunction with an infra-red receiving device.

5. A machine according to any one of claims 1 to 4, wherein stopping of the roller after rotation thereof through the said predetermined angle is effected as a consequence of mechanical operation of a limit switch by an operating member connected to the roller.

6. A machine according to claim 5, wherein the said operating member is positionally adjustable.

7. A machine according to any one of claims 1 to 4, wherein a timer is incorporated in the said control circuit so that the roller is brought to rest a predetermined period after commencement of rota tion thereof.

8. A machine according to any one of claims 1 to 7, wherein said printing roller defines a nip with a counter roller and a feed surface is provided level with the nip at the inlet side thereof.

9. A machine according to claim 8, wherein a feed table is provided level with but spaced from the said feed surface and a feed roller is provided in such splice with wheels pressing thereon whereby an art cle to be printed can be advanced from the feed tat ie to the feed surface by the feed roller.

0. A machine according to any one of claims 1 to 3, having an inking mechanism comprising inking rollers which pick up ink from an ink tray and apply same to the printing roller.

11. A machine according to claim 8 or any claim dependent thereon wherein spaced feed surfaces are provided level with the nip at the outlet side thereof and a feed roller is provided in such space with wheels pressing thereon whereby a printed article can be advanced from one to the other of said outlet feed surfaces by the said associated feed roller.

12. A machine according to any one of claims 1 to 11, including an outlet conveyor adapted to receive printed articles and convey same through a drying tunnel.

13. A printing machine substantially as hereinbefore described with reference to and illustrated in the accompanying drawings.