Liquid glue applying device

Abstract

 This invention relates to a liquid glue applying device comprising a small tank (1) containing the glue and a roller (2) dipped in the glue. The tank (1) communicates, in the communicating vessels fashion, through a flexible hose (3) with a reservoir (4) which supplies the glue. This reservoir (4) is movable vertically and is raised automatically under the control of a sensor (12) responsive to the level of the glue in the tank (1), so as to maintain this level substantially constant.

Description

[0001] This invention relates to a liquid glue applying device comprising a small tank which contains the glue and a roller dipped in the glue, and is connected to a glue-supplying reservoir, sensor means being provided which are responsive to the level of the glue in the tank and which control automatically the flow of the glue from the feeding reservoir to the tank, so as to maintain the level of the glue in the tank substantially constant.

[0002] These glue-applying devices are used, for example, in the packaging field, and particularly in the tobacco industry, for example, in the manufacture of cigarettes for glueing the strips connecting the filter tips to the cigarettes. The roller dipped in the glue within the tank may have the function of a pick-up roller which picks up the glue and transfers it to smearing members, such as rollers or sectors, which apply the glue onto the surfaces to be glued. In other known embodiments, the dipping roller may also act as a smearing roller and may apply the glue directly onto the surfaces to be glued.

[0003] In order to obtain a reliable operation of a glue-applying device of the type mentioned above, it is necessary that the level of the liquid glue in the tank be maintained substantially constant.

[0004] For this purpose, the tank, having usually a very limited capacity, is connected to a glue-supplying reservoir which has a considerably greater capacity than said tank. When the level of the glue in the tank falls to a given extent below the optimum level, sensor means responsive to the level of the glue cause an amount of glue to flow automatically from the supplying reservoir into the tank, such as to reinstate the optimum level.

[0005] Any suitable level-sensing means may be used, for example, capacitive sensing means.

[0006] In the heretofore-known glue-applying devices of the type mentioned above, in order to transfer liquid glue from the supplying reservoir to the tank so as to maintain a constant level in the latter, the tank is connected to the supplying reservoir by a pump which is controlled by level-sensing means associated with said tank. In another known embodiment, the supplying reservoir is sealingly closed and the transfer of the liquid glue from this reservoir to the tank is effected by the action of pressurized air in the reservoir above the level of the glue. For this purpose, the level-sensing means associated with the tank controls a solenoid valve for admitting pressurized air in the upper portion of the sealingly-closed supplying reservoir.

[0007] The invention aims to improve a glue-applying device of the type described in the preamble, so as to automatically maintain the level of the liquid glue in the tank by constructionally simpler and more economical means yet affording a greater operational reliability.

[0008] This problem is solved by the invention in that the reservoir which supplies the liquid glue is movable vertically and its lower portion is connected to the lower portion of the tank by means of a tubing which is at least partly flexible and/or articulated and in the communicating vessels fashion, whereby the same level will be maintained both in the tank and reservoir, while the level-sensing means associated with the tank controls a motivating means for the supplying reservoir so as to lift said reservoir depending upon the consumption of the glue and to maintain the level of the glue in the tank substantially constant.

[0009] These and further characteristics of the invention and the advantages resulting therefrom will be apparent from the following description of a preferred embodiment of a glue-applying device which is diagrammatically shown in the vertical sectional view of the single Figure of the accompanying drawing.

[0010] In the drawing, the numeral 1 indicates a small tank containing liquid glue, usually of not too high viscositu, wherein is dipped a roller 2 for picking and, optionally, smearing the glue.

[0011] The tank 1 is connected at the bottom thereof, through a flexible hose 3, to the lower portion of a glue-supplying reservoir 4. The tank 1 has a relatively limited capacity, while the capacity of the reservoir 4 is appreciably larger than that of the tank 1. Interposed between the tank 1 and the flexible hose 3 is a stop valve 5. A further stop valve 6 is interposed between the reservoir 4 and the flexible hose 3. These valves 5 and 6 permit the disassembling in case of maintenance operations.

[0012] The tank 1 is arranged in a stationary position during the operation, while the reservoir 4 is mounted on a supporting member 7 which is guided to be movable in a vertical direction so as to permit a corresponding lifting and lowering movement of said tank 4. At least the lifting movement of the support 7, and therefore of the reservoir 4, may be caused by an actuator for example an electric motor 8, for example, by means of a pinion-and-rack drive 9-10.

[0013] The motor 8 is controlled, through a control device 11, by a stationary sensor 12 which is responsive to the level of the liquid glue in the tank 1 and, preferably, also by a stationary sensor 13 which is responsive to the level of the liquid glue in the supplying reservoir 4.

[0014] When the device is designed to apply glues whose components tend to dissociate and form deposits, such as, for example, polyvinyl-acetate glues, the supplying reservoir 4 may comprise therein a rotary stirrer 14 activated by a motor 15 mounted on said reservoir 4.

[0015] The glue-supplying reservoir 4 may be provided with a suitable cover 16 to prevent any dirt or foreign matter from entering the reservoir, but the latter shall not be closed hermetically, that is the interior of the tank 4 shall be at the atmospheric pressure.

[0016] When the valves 5 and 6 are open, the same level of liquid glue will be established in the supplying reservoir 4 and tank 1 on the basis of the principle of the communicating vessels. When the reservoir is intially full, it will be lowered to a lower position wherein the level of the glue in the tank 1 is the optimum level for the operation of the glue-applying device. The level sensor 12 associated with the tank 1 is adjusted to this optimum level to be maintained substantially constant. The level-sensor 13 associated with the supplying reservoir 4 is, however, adjusted to a level slightly above said optimum level of the glue in the tank 1 but below the level whereat the glue would overflow from said tank 1. When, during the operation of the glue-applying device, the level of the glue in the tank 1 falls - due to the consumption of glue - a pre-established value below the optimum level, the level sensor 12 associated with the tank 1 activates the motor 8 so as to cause the lifting of the support 7 and, therefore, of the whole supplying reservoir 4 to such an extent as to reinstate the optimum level of the glue in the tank 1. Thereafter, these operations will be repeated automatically and intermittently until the glue in the reservoir 4 is exhausted and until the latter has been lifted up to a corresponding top end position. The reservoir 4 is then filled up again and lowered to its starting lower position. This lowering movement may be effected either manually or by said actuator or motor 8 that lifts said reservoir 4 when said actuator or motor 8 is of the reversible or double-acting type and, for example, is formed by a motor having two directions of rotation.

[0017] In case of an obstruction in the flexible hose 3 and/or stop valves 5,6, upon the next lifting step of the supplying reservoir 4, the level of the glue in the reservoir 4 is lifted together with the reservoir, as far as the sensor 13 associated with said reservoir 4. When said sensor 13 is responsive to the level of the glue in the reservoir 4, it stops - through the control device 11 - any further lifting of the reservoir 4. Thus, the risk is avoided that, after the removal of said obstruction, the level of the glue in the tank 1 rises beyond the upper edge of the tank 1 and the glue overflows therefrom.

[0018] Of course, the invention is not limited to the embodiment just described and illustrated, but broad changes and modifications, especially of constructional nature, may be made thereto. Thus, for example, the lifting and lowering movements of the glue-supplying reservoir 4, instead of being a vertical translatory movement, as illustrated, may be an angular movement, for example, if the supplying reservoir 4 is mounted on a vertically rocking arm. The level-sensors 12,13 associated with the tank 1 and supplying reservoir 4 may also be worked out in any suitable manner and may be constituted, for example, by capacitive sensors.

Claims

1. A liquid glue applying device, comprising a small tank (1) which contains the glue and a roller (2) dipped in the glue and is connected to a glue-supplying reservoir (4), sensing means (12) being provided which is responsive to the level of the glue in the tank (1) and controls automatically the flow of glue from the supplying reservoir (4) to the tank (1) so as to substantially maintain the level of glue in the tank (1) constant, characterized in that the supplying reservoir (4) may be lifted and lowered and its lower portion is connected to the lower portion of the tank (1) in the communicating vessels fashion through a tube (3) which is at least partly flexible or articulated, whereby the same level will be established in the tank (1) and reservoir (4), while the level-sensing means (12) associated with the tank (1) controls an actuator (8) for the supplying reservoir (4) and, when the level of the glue in the tank (1) falls below a pre-established level, causes the lifting of the supplying reservoir (4) so as to reinstate the pre-established level in the tank (1).

2. A device according to claim 1, characterized in that the glue-supplying reservoir (4) may be lifted by its actuator (8) and may be lowered manually.

3. A device according to claim 1, characterized in that the glue-supplying reservoir (4) may be lifted and lowered by means of a double-acting actuator, particularly by a reversible electric motor (8).

4. A device according to one or more of the preceding claims, characterized, in that the glue-supplying reservoir (4) may be lifted and lowered with a vertical translatory movement.

5. A device according to one or more of the claims 1 to 3, characterized in that said glue-supplying reservoir (4) may be lifted and lowered with a vertical rocking movement.

6. A device according to one or more of the preceding claims, characterized by stop valves (5,6) at the unions of the tube (3) communicating to the tank (1) and/or glue-supplying reservoir (4).

7. A device according to one or more of the preceding claims, characterized in that the glue-supplying reservoir (4) has associated therewith a level-sensing means (13) which is adjusted to a top permitted level which is higher than the pre-established level in the tank (1) but is lower than the overflow top edge of said tank (1), and which causes automatically the discontinuation of the lifting movement of the supplying reservoir (4) when it senses said top permitted level.

8. A device according to one or more of the preceding claims, characterized in that a stirrer (14,15) is arranged in the glue-supplying reservoir (4).

Drawing