AU704577B2 - Bag tying machine - Google Patents

Description

The present invention relates to a machine for sealing the open end of a bag by clamping a length of adhesive tape around the gathered together neck of the bag.

Machines for sealing the open end of a bag are known from our earlier patent specifications, GB-1,381,871 and GB-l,517,031. In the machine disclosed in GB-I,381,871, the open end of the bag to be sealed is received in a guide in the machine, which may comprise either a pair of counter-rotating wheels or opposed endless belts.

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follow-up member initially disposed behind the open end of the bag in the direction of movement of the bag is moved to s push the open end of the bag in the direction of movement of the bag and against a retractable stop. The open end of the bag gathers up against the retractable stop. The retractable stop is retracted, allowing the gathered together neck of the bag to be pushed by the follow up S 20 member onto an adhesive tape positioned across the path of the open end of the bag. A pair of opposed clamp means clamp the length of adhesive tape around the gathered together neck of the bag to thereby seal the bag. The clamp means, retractable stop, and follow-up member are returned to their initial positions ready to receive the next bag.

S94 The adhesive tape is supplied from a reel of tape, and is pulled across the path of the open end of the bag by a gripper. When the neck of the bag contacts the adhesive tape, the tape is severed from the reel by a knife, and released from the gripper. After the bag is sealed, the gripper pulls adhesive tape from the reel across the path of the open end of the next bag to be sealed.

The machine disclosed in GB 1,517,031 is generally similar to that of GB 1,381,871 except that the retractable stop is omitted, and the open end of the bag is pushed directly onto the adhesive tape by the follow-up member, and is gathered together on the adhesive tape.

In the machines of both GB 1,381,871 and GB 1,517,031 the follow-up member, gripper, knife, clamping means, tape feed and guide are all driven through a series of cams, gears, links and followers from a single motor. In this way, the sequence and relative timing of the operation of each of these components is fixed. This mechanical arrangement requires the machine to be robust to ensure reliability of operation, and consequently the machine housing is conventionally cast. In commercialised machines based on our patents, the bag sealing machine has S 15 invariably been associated with a flighted conveyor with the functions of the feed belt and pusher mechanism being mechanically driven from the conveyor motor via a chain.

In this way, the operation of the bag tying machine is synchronised with the conveyor carrying the bags to be sealed. In operation, bags to be sealed are placed on the conveyor, and abut against a flight on the conveyor.

In this way, the position of the bag is accurately known, and the timing of the operation of the sealing machine is matched to the supply of bags to be sealed. If a bag is detected on the conveyor, the sealing machine will operate to clamp the neck of the bag in the manner described above.

If no bag is detected on the conveyor, the sealing machine will not operate. These commercialised machines must be robust and of high quality to allow them to operate accurately with an existing conveyor. Accordingly, these machines are expensive.

According to the present invention, a sealing machine includes a guide for receiving the open end of a bag to be sealed, a follow-up member arranged to push the open end of a bag towards an adhesive tape, a clamping means arranged to clamp the adhesive tape around the gathered together neck of the bag, a gripper to pull a length of adhesive tape across the path of the open end of the bag, a first sensor to detect the presence of a bag for controlling movement of the follow-up member, and a second sensor to detect when the open end of the bag contacts the adhesive tape to control the operation of the gripper.

This arrangement is advantageous over the prior art in that the machine is controlled by sensing the presence and position of the open end of a bag to be sealed, and the operation of individual steps in the sealing of the bag is controlled by these sensors. In this way, it is no longer necessary to combine the sealing machine with a specific conveyor as the machine may be driven by its own drive, 15 and needs no synchronisation, and therefore the apparatus may be produced at a lower cost, and much lighter, thereby Smaking the machine less expensive. Further, it is not necessary to use a flighted conveyor, and therefore the machine may be positioned beside any existing conveyor in 20 a packaging line to seal bags. A flighted conveyor may be used to convey the open bags to the sealing machine, this ensuring that the bags do not slip on the conveyor as they are sealed, and that the bags remain square across the conveyor.

It is preferred that the machine includes a knife arranged to sever the adhesive tape. It is advantageous for the second sensor to also control the severing of the adhesive tape, and subsequent release of the adhesive tape from the gripper prior to the clamping of the tape around the gathered together neck of the bag.

A third sensor may be provided to control the operation of the gripper to grip the adhesive tape and pull this across the path of the neck of the bag.

The present invention will be described with respect to the accompanying Figures which show a side view of a bag sealing machine at different stages of the bag sealing process.

The bag tying machine of the present invention is located beside a conveyor carrying open bags to be sealed.

The conveyor may be a flighted conveyor having ridges extending across the conveyor transverse to the direction of movement. In this case, the bags abut the ridges, thereby preventing the bags from slipping on the conveyor, or becoming skewed. Alternatively, any other conveyor ,suitable for conveying the bags may be used. A rotating brush or pairs of brushes, draws the open end of the bag 15 into the bag tying machine to a guide comprising a pair of endless belts 1, 2 running in opposite directions as indicated in Figure i. The brushes may be driven by a dedicated motor having a lower power, this ensuring that the brushes will stop if, for example, an operator's hand 20 is caught between them. The endless belts 1, 2 move the open end of the bag through the bag tying machine in the same direction as the bag is conveyed by the conveyor. As the open end of the bag is moved, an arm 3 is caused to pivot as the open end of the bag passes it. After the bag passes the arm 3, the arm 3 drops back to the vertical.

The movement of the arm is detected by a sensor 4. This sensor may be a light emitter-detector or any other form of sensor which detects the presence or absence of the arm 3.

Upon detection of the return movement of the arm 3, and hence of the open end of a bag, a pneumatic cylinder is operated to move a follow-up member 6. The follow-up member 6 includes a bag receiving recess 11 into which the open end of a bag to be sealed may be gathered. The follow-up member 6 is pivotally mounted on a runner block 7, the runner block 7 being restricted to movement along a guide rail (not shown) running parallel to the direction of movement of the open end of the bag. The follow-up member 6 is pivotally mounted to a first arm 8, which is in turn pivotally mounted to a second arm 9, which is pivotally mounted to the pneumatic cylinder 5. The second arm 9 is pivotally mounted by a pivot pin 10 to the body of the machine. Operation of the pneumatic cylinder 5 pivots the second arm 9, anti-clockwise, about the pivot pin causing the first arm 8 to move generally in the direction of movement of the open end of the bag. This causes the follow-up member 6 to pivot with respect to the runner block 7 causing the bag receiving recess 11 of the followup member 6 to raise behind the open end of the bag.

Continued operation of the pneumatic cylinder 5 and consequent movement of the first and second arm 8, 9 causes 15 the runner block 7 to slide along the guide rails, and *99999 moves the follow-up member 6 in the direction of movement of the open end of the bag, pushing the open end of the bag towards the adhesive side of an adhesive tape 12.

The open end of the bag is collected between a pair of opposed leaf springs 22. This causes the neck of the bag to collect together. Once the neck of the bag is gathered, this passes through the opposed leaf springs 22, and onto the adhesive tape 12. By gathering the neck of the bag in the leaf springs 22, the neck is gathered more effectively than by merely pushing the neck against the adhesive tape 12, and causes a short delay sufficient to allow the grippers 15 to pull the length of adhesive tape 12 across the path of the open neck of the bag.

A sensor 13 detects when the open end of a bag contacts the adhesive tape 12. This sensor 13 may be associated with the pneumatic cylinder 5, in which case the sensor 13 detects a pre-determined movement of the cylinder 5 which corresponds to a positioning of the bag receiving recess 11 of the follow-up member 6 adjacent the adhesive tape 12. Other examples of suitable sensor includes a pressure sensor which detects an increase in tension of the tape due to the bag coming into contact with the tape, or a proximity sensor detecting the presence of either the end of the bag or the follow-up member 6. As the open end of the bag is pushed against the tape 12, the end of the bag is gathered together.

Upon detection of the open end of the bag coming in contact with the adhesive tape 12, the adhesive tape 12 is cut by a knife 18. This gives a length of tape adhered at its mid-point to the gathered together neck of the bag.

Subsequently the length of tape is released from grippers originally holding the tape 12. As the follow-up member 6 continues to push the open end of the bag, the bag and length of adhesive tape 12 are pushed between two opposed clamping means 16, 17 which wrap the tape 12 around the gathered together neck of the bag. The clamping means 16, 17 are pivotally mounted about points 19, and are biased towards each other by springs 20, 21. The tension of the 20 springs is adjustable to control the force with which the clamping means 16, 17 are biased towards each other.

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retractable stop may also be provided which restricts the movement of the neck of the bag behind the adhesive tape 12 ~as this is wrapped around the neck before allowing the bag to pass. The retraction of this stop may be achieved by a pneumatic control.

As the neck of the bag is pushed through the clamping means 16, 17, a pneumatic cylinder (not shown) moves the grippers 15 upwards towards the tape 12 remaining on the tape reel. A sensor detects when the grippers 15 reach their upper limit. This sensor may either be provided on the pneumatic cylinder, or may be a proximity sensor which detects the presence of the grippers 15. Upon detection the grippers 15 are at their upper limit, the grippers are closed, thereby gripping the end of the tape 12. The grippers 15 are then lowered, pulling the adhesive tape 12 across the path of open ends of bags. The pneumatic cylinder 5 also operates to rotate the second arm 9 clockwise to retract the follow-up member 6 to the start position as shown in Figure 1. A biasing means is provided to urge the bag receiving recess 11 of the follow-up member 6 upwards as the follow-up member 6 is initially retracted, ensuring that the bag receiving recess 11 initially remains at the same height as the path of the open neck of the bag through the machine.

*oo o o* THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:- 1. A sealing machine including a guide for receiving the open end of a bag to be sealed, a follow-up member arranged to push the open end of a bag towards an adhesive tape, a clamping means arranged to clamp the adhesive tape around the gathered together neck of the bag, a gripper to pull a length of adhesive tape across the path of the open end of the bag, a first sensor to detect the presence of a bag for controlling movement of the follow-up member, and a second sensor to detect when the open end of the bag S. contacts the adhesive tape to control an operation of the 15 gripper.

2. A sealing machine according to claim 1, further comprising a knife arranged to sever the adhesive tape.

3. A sealing machine according to claim 2, in which the second sensor is also arranged to control both the severing of the adhesive tape, and an operation of the gripper, the p.

operation of the gripper being the release of the adhesive tape from the gripper prior to the clamping of the tape around the gathered together neck of the bag.

A sealing machine according to any one of the preceding claims, further comprising a third sensor to further control the operation of the gripper to grip the adhesive tape and pull this across the path of the neck of the bag.

A sealing machine substantially as hereinbefore described with reference to the drawings.

DATED this 10th day of February, 1999.

THURNE ENGINEERING COMPANY LIMITED By its Patent Attorneys: DAVIES COLLISON CAVE