Apparatus and method for applying cover sheets to ends, preformed into cross bottoms, of tube portions

Abstract

A device and a method for applying cover sheets to cross-bottoms of tubular sections made of a plastic material. The device includes conveyor devices for transporting the tubular sections and for depositing the cover sheets on the cross-bottoms in a deposit area. The device includes a hot gas device with a gas heater and a nozzle connected to the gas heater and oriented toward the deposit area for the cover sheets so when gas is supplied to the gas heater, the gas flows along a flow path from the gas supply through the gas heater and the nozzle into the deposit area. The hot gas device has a hot gas reservoir with an internal volume for the temporary storage of hot gas, the flow path running through the hot gas reservoir. A gas mass flow ({dot over (m)}1, {dot over (m)}2, {dot over (m)}ges) of gas supplied to the gas heater is adjustable by a control.

Claims

1. A device for applying cover sheets to ends of tubular sections made of a plastic material, the ends having been preformed into cross-bottoms, comprising: a conveyor operable to transport the tubular sections and to transport and deposit the cover sheets on the cross-bottoms of the tubular sections in a deposit area while the tubular sections are being conveyed, and a hot gas device with a gas heater operable to heat gas, and a nozzle connected to the gas heater and oriented toward the deposit area for the cover sheets, wherein the gas heater is connectable to a gas supply and, when gas is supplied to the gas heater, the gas flows along a flow path from the gas supply through the gas heater and the nozzle into the deposit area, wherein the hot gas device further comprises a hot gas reservoir with an internal volume for the temporary storage of hot gas wherein the hot gas reservoir is located between the nozzle and the gas heater, and the flow path running through the hot gas reservoir, and wherein a gas mass flow ({dot over (m)}.sub.1, {dot over (m)}.sub.2, {dot over (m)}.sub.ges) of gas supplied to the gas heater is adjustable by a control, wherein the control is operable to temporarily increase the gas mass flow ({dot over (m)}.sub.1, {dot over (m)}.sub.2, {dot over (m)}.sub.ges) of gas supplied to the gas heater from a basic mass flow ({dot over (m)}.sub.1) by a pulse mass flow ({dot over (m)}.sub.2) to a total mass flow ({dot over (m)}.sub.ges).

2. The device according to claim 1, wherein one volume of the pulse mass flow ({dot over (m)}.sub.2) is one fifth to one twentieth of the internal volume of the hot gas reservoir.

3. The device according to claim 2, wherein the gas supply comprises at least one compressor and/or at least one compressed air reservoir and an injector, wherein at least one constantly running compressor is operable to generate the basic mass flow ({dot over (m)}.sub.1) of gas supplied to the gas heater and the injector is operable to generate the pulse mass flow ({dot over (m)}.sub.2) by at least one second compressor and/or at least one compressed air reservoir, as is operable to supply the pulse mass flow ({dot over (m)}.sub.2) to the basic mass flow ({dot over (m)}.sub.1), to generate the total mass flow ({dot over (m)}.sub.ges).

4. The device according to claim 1, wherein the hot gas reservoir has a tubular configuration.

5. The device according to claim 1, wherein the gas supply is a component of the device operable to apply cover sheets to ends of tubular sections made of a plastic material, the ends having been preformed into cross-bottoms, and the gas supply comprises at least one compressor and/or at least one compressed air reservoir.

6. The device according to claim 1, wherein the conveyor comprises a belt conveyor or a band conveyor operable to transport the tubular sections, and the conveyor further comprises a suction cylinder operable to transport the cover sheets.

7. The device according to claim 1, wherein a size of the internal volume of the hot gas reservoir is adjustable.

8. A method for applying cover sheets to ends of tubular sections made of a plastic material, the ends having been preformed into cross-bottoms, wherein the ends preformed into cross-bottoms each have a first outer triangular area, a first inner triangular area, a second outer triangular area, a second inner triangular area and a central area, wherein, in a longitudinal bottom direction, the first inner triangular area is arranged between the first outer triangular area and the central area, and the second inner triangular area is arranged between the second outer triangular area and the central area, the method comprising operations of: a) transporting the tubular sections in a conveying direction, the longitudinal bottom direction of the cross-bottoms being in parallel to the conveying direction; b) transporting the cover sheets in the conveying direction; c) while the tubular sections are being conveyed, always placing one cover sheet on a cross-bottom in a deposit area, when one of the cross-bottoms passes the deposit area, wherein the method furthermore comprises supplying a gas with a mass flow ({dot over (m)}.sub.ges) to a hot gas device while the cover sheet is being applied, the hot gas device comprising a gas heater, a hot gas reservoir and a nozzle which configured to direct heated gas into the deposit area, and wherein: the gas is supplied to the hot gas device with an increased mass flow ({dot over (m)}.sub.ges), while the first inner triangular area of a cross-bottom passes the deposit area; the gas is supplied to the hot gas device with a reduced mass flow ({dot over (m)}.sub.1), while the central area of a cross-bottom passes the deposit area; and the gas is supplied to the hot gas device with an increased mass flow ({dot over (m)}.sub.ges), while the second inner triangular area of a cross-bottom passes the deposit area.

9. The method according to claim 8, wherein the tubular sections are transported at a distance from one another — viewed in the conveying direction —wherein the increased mass flow ({dot over (m)}.sub.ges) of gas supplied to the hot gas device is reduced, while there is no first inner triangular area, second inner triangular area or central area of a cross-bottom in the deposit area.

10. The method according to claim 9, wherein the increased mass flow ({dot over (m)}.sub.ges) of gas supplied to the hot gas device is reduced as soon as the second inner triangular area of a cross-bottom has passed the deposit area.

11. The method according to claim 8, wherein the reduced mass flow ({dot over (m)}.sub.1) of gas supplied to the hot gas device is increased shortly before the first inner triangular area of the cross-bottom reaches the deposit area.

12. The method according to claim 8, wherein the increased mass flow ({dot over (m)}.sub.ges) of gas supplied to the hot gas device is reduced as soon as the central area enters the deposit area.

13. The method according to claim 8, wherein the reduced mass flow ({dot over (m)}.sub.1) of gas supplied to the hot gas device is increased as soon as the second inner triangular area enters the deposit area.

Description

(1) Further advantageous embodiments of the device according to the invention and of the method according to the invention for applying cover sheets to ends of tubular sections preformed into cross-bottoms are explained in further detail below with reference to the figures.

(2) FIG. 1 shows individual processing steps for forming ends of tubular sections into cross-bottoms.

(3) FIG. 2 shows an embodiment of a device according to the invention for applying cover sheets to the ends of tubular sections formed into cross-bottoms in a schematic view.

(4) FIGS. 3 and 4 show a hot gas means of the device according to the invention as a simplified system.

(5) FIG. 5 shows a chart of the temperatures prevailing in the simplified system according to FIGS. 3 and 4 as a function of a gas mass flow supplied to the hot gas means.

(6) FIG. 1 shows, in a greatly simplified manner, individual processing steps A to E for forming ends 1 of tubular sections 2 into cross-bottoms 3 and applying a cover sheet 9 to the finished cross-bottoms 3. During the implementation of the processing steps A to E, the tubular sections 2 are transported on a conveyor belt 4 in the conveying direction 5 while lying flat at a distance 38 from one another, with tube layers 6 abutting one another.

(7) In processing step A, the ends 1 of the tubular sections 2 are folded over by 90 degrees.

(8) In processing step B, the tube layers 6 are pulled apart, whereby the ends 1 are opened. By folding down the opened ends 1, tabs 8 are formed.

(9) In processing step C, a valve patch 7 is inserted into at least one opened end 1 that has been pulled apart and is at least partially welded or glued to the opened end 1.

(10) In processing step D, the tabs 8 are folded over, whereby a cross-bottom 3 is formed at one end 1 in each case. As a result of folding, each cross-bottom 3 has a first inner triangular area 12, a first outer triangular area 41, a second inner triangular area 13, a second outer triangular area 42 and a central area 14, wherein, in the longitudinal bottom direction 11, the first inner triangular area 12 is arranged between the first outer triangular area 41 and the central area 14, and the second inner triangular area 13 is arranged between the second outer triangular area 42 and the central area 14. The tubular sections 2 are oriented on the conveyor belt 4 in such a way that the longitudinal bottom direction 11 of the cross-bottoms 3 is in parallel to the conveying direction 5.

(11) In processing step E, a cover sheet 9 is placed with a device 15 according to the invention as per FIG. 2 on the ends 1 of the tubular sections 2 preformed into cross-bottoms 3 and is welded thereto. The device 15 according to the invention is not illustrated in FIG. 1 for reasons of clarity. The bag 10 completed by processing step E can now be filled with material. Processing devices for performing the processing steps A to D are sufficiently well known and are therefore not explained in further detail.

(12) It should also be pointed out that a cross-bottom 3 may also be formed only at one end 1 of the tubular sections 2, if the bag is to be used as a sachet, for example.

(13) FIG. 2 shows an embodiment of a device 15 according to the invention in a schematic view. The device 15 comprises conveying means for transporting the tubular sections 2 and the cover sheets 9. The conveying means for transporting the tubular sections 2 is formed by the conveyor belt 4, which transports the tubular sections 2 according to FIG. 1 past all the stations for processing steps A to E. However, the conveying means for transporting the tubular sections 2 may also be formed by an independent conveyor belt, wherein the processing steps A to E are carried out at stations on at least one separate conveyor belt.

(14) The conveying means for transporting the cover sheets 9 is formed by a conveying device 17. The conveying device 17 comprises a cutting cylinder 18, a transfer cylinder 19, a suction cylinder 20 and a conveying path 21. The cover sheets 9 are cut from an endless band 22 by means of blades 40 arranged on the cutting cylinder 18 and the transfer cylinder 19 and are supplied across the transfer cylinder 19 and the conveying path 21 to the suction cylinder 20. The suction cylinder 20 always places one cover sheet 9 on a cross-bottom 3 in a deposit area 23, while the tubular sections 2 are conveyed in the conveying direction 5 and pass the deposit area 23. The speed of the tubular sections 2 and the cover sheets 9 is identical when they are placed, with both the cover sheets 9 and the tubular sections 2 being transported in the conveying direction 5 when they are placed. The depositing of the cover sheets 9 on the cross-bottoms 3 takes place starting at the first inner triangular area 12 and continues over the middle area 14 and the second inner triangular area 13, whereby a gap is created in the deposit area 23 between the cover sheet 9 and the cross-bottoms 3 as a result of successive depositing.

(15) The device 15 according to the invention also comprises a hot gas means 24. The hot gas means 24 is connected to a gas supply. The gas supply is formed by a compressor in the form of a fan 25, a compressed air distributor 28 and an injector 29. The fan 25 connects to the compressed air distributor 28 via a connecting tube 26. The injector 29 connects directly to the compressed air distributor 28. The compressed air distributor 28 connects to the hot gas means 24. Via a tube 16, the injector 29 is connected to an external compressed air supply, which is not illustrated any further. The fan 25 comprises an intake funnel 27. The fan 25 and the injector 29 can be part of the device 15, or may also be designed separately. There is also the possibility that the gas supply is formed by a compressor, a fan and/or a compressed air reservoir.

(16) The hot gas means 24 comprises a gas heater 30, a hot gas reservoir 31 and a nozzle 32, which is directed into the deposit area 23 for the cover sheets 9. The hot gas reservoir 31 connects directly to the gas heater 30, and the nozzle 32 connects directly to the hot gas reservoir 31.

(17) If a gas mass flow is now supplied by the gas supply to the hot gas means 24, gas will flow along a flow path 33 from the gas supply through the gas heater 30, the hot gas reservoir 31 and the nozzle 32 into the deposit area 23.

(18) The hot gas reservoir 31 has an internal volume 36 and a tubular design. A diameter of the tubular internal volume 36 is essentially equal to an inner diameter of the connecting tube 26. The inner volume 36 is sheathed with an insulating layer 37 in order to keep heat losses as low as possible.

(19) The device 15 according to the invention comprises a control 34. The control 34 is connected to the fan 25 and the injector 29 for communication. The gas mass flow of gas supplied to the hot gas means 24 is adjustable by means of the control 34.

(20) FIGS. 3 and 4 show the hot gas means 24 of the device 15 according to the invention as a simplified system 35.

(21) FIG. 5 shows a chart of the temperatures prevailing in the simplified system 35 according to FIGS. 3 and 4 as a function of a gas mass flow supplied to the hot gas means 24.

(22) The function of the device 15 according to the invention will now be explained in further detail with reference to FIGS. 3 to 5. For this purpose, the gas mass flow of gas supplied to the hot gas means is viewed more closely while a cross-bottom 3 passes the deposit area 23.

(23) As soon as the first inner triangular area 12 of a cross-bottom 3 enters the deposit area 23, the gas mass flow emitted from the nozzle 32 hits the first inner triangular area 12. Shortly before the first inner triangular area 12 reaches the deposit area 23, i.e., shortly before the gas mass flow that is emitted from the nozzle 32 no longer hits the conveyor belt 4 or, respectively, the first outer triangular area 41 at the distance 38, but rather hits the first inner triangular area 12, the gas mass flow supplied to the hot gas means 24 is increased from a basic mass flow {dot over (m)}.sub.1 to a total mass flow {dot over (m)}.sub.ges. See FIG. 5.

(24) The hot gas reservoir 31 is charged with gas at a temperature T.sub.H—referred to below as a hot charge gas.

(25) The total mass flow {dot over (m)}.sub.ges is composed of the basic mass flow {dot over (m)}.sub.1 and a pulse mass flow {dot over (m)}.sub.2. The basic mass flow {dot over (m)}.sub.1 is produced by the fan 25, and the pulse mass flow {dot over (m)}.sub.2 is produced via the injector 29. In this regard, see in particular also FIG. 3.

(26) Since the mass balance across the entire system 35 must be zero, the mass flow through the hot gas means 24 is constant and corresponds to the total mass flow {dot over (m)}.sub.ges. This means that the mass flow of the gas which emerges from the hot gas reservoir 31 at the nozzle 32 is equal to the mass flow of the gas which is supplied to the hot gas means 24.

(27) A heat {dot over (Q)}.sub.mges,0 is supplied to the gas heater via the gas supplied to the gas heater 30 via the total mass flow {dot over (m)}.sub.ges. This is calculated from the basic mass flow {dot over (m)}.sub.1 and the pulse mass flow {dot over (m)}.sub.2, the specific heat capacity of the gas and the temperature T.sub.0 of the basic mass flow {dot over (m)}.sub.1 and the pulse mass flow {dot over (m)}.sub.2.

(28) In the gas heater 30, a thermal heat flow {dot over (Q)}.sub.H is supplied via a heating element, which is not illustrated. As a result, the temperature of the total mass flow {dot over (m)}.sub.ges is raised from T.sub.0 to T.sub.N and a heat flow {dot over (Q)}.sub.mges,1 is transferred with the gas into the hot gas reservoir 31. The temperature T.sub.GE at the outlet of the gas heater 30 is equal to T.sub.N. See FIG. 5.

(29) The gas fed into the hot gas reservoir 31 at the temperature T.sub.N displaces the hot charge gas from the hot gas reservoir 31 via the nozzle 32 and fills the hot gas reservoir 31 with gas at the temperature T.sub.N—referred to below as a cold charge gas. The temperature T.sub.HR of the hot charge gas discharged at the hot gas reservoir 31 or, respectively, the nozzle 32 is equal to T.sub.H. The hot charge gas introduces a heat flow {dot over (Q)}.sub.mges,2 into the deposit area 23. This is calculated from the total mass flow {dot over (m)}.sub.ges, the specific heat capacity of the gas and the temperature T.sub.H of the hot charge gas.

(30) At the moment when the central area 14 of the cross-bottom 3 enters the deposit area 23, the gas mass flow supplied to the hot gas means 24 is reduced from the total mass flow {dot over (m)}.sub.ges by the pulse mass flow {dot over (m)}.sub.2 to the basic mass flow m.sub.1. For this purpose, the injector 30 is switched off by the control 34.

(31) The total mass flow {dot over (m)}.sub.ges and the internal volume 36 are coordinated such that the hot gas reservoir 31 is filled with the cold charge gas, but no cold charge gas leaves the hot gas reservoir 31, while the gas mass flow supplied to the hot gas means 24 corresponds to the total mass flow {dot over (m)}.sub.ges. Correspondingly, the hot gas reservoir 31 is filled with cold charge gas during the switching from the total mass flow {dot over (m)}.sub.ges to the basic mass flow {dot over (m)}.sub.1.

(32) Due to the mass balance in the entire system 35, the mass flow corresponds to the basic mass flow {dot over (m)}.sub.1 after switching to the basic mass flow m.sub.1. A heat flow {dot over (Q)}.sub.m1,0 is supplied to the gas heater 30 via the gas supplied to the gas heater 30 via the basic mass flow m.sub.1. This is calculated from the basic mass flow {dot over (m)}.sub.1, the specific heat capacity of the gas and the temperature T.sub.0 of the basic mass flow m.sub.1 See in particular FIG. 4.

(33) In the gas heater 30, the thermal heat flow {dot over (Q)}.sub.H is supplied via the heating element. The thermal heat flow {dot over (Q)}.sub.H is constant. As a result, the temperature of the basic mass flow {dot over (m)}.sub.1 is raised from T.sub.0 to T.sub.H, and a heat flow {dot over (Q)}.sub.m1,1 is transferred with the gas into the hot gas reservoir 31. The temperature T.sub.GE at the outlet of the gas heater 30 is equal to T.sub.H, wherein the following applies due to the lower mass flow supplied and the constant thermal heat flow {dot over (Q)}.sub.H:T.sub.H>T.sub.N.

(34) The gas fed into the hot gas reservoir 31 at the temperature T.sub.H displaces the cold charge gas from the hot gas reservoir 31 via the nozzle 32 and fills the hot gas reservoir 31 with hot charge gas at the temperature T.sub.H. The temperature T.sub.HR of the cold charge gas discharged at the hot gas reservoir 31 or, respectively, the nozzle 32 is equal to T.sub.N. The cold charge gas introduces a heat flow {dot over (Q)}.sub.m1,2 into the deposit area 23. This is calculated from the basic mass flow m.sub.1, the specific heat capacity of the gas and the temperature T.sub.N of the cold charge gas.

(35) At the moment when the second inner triangular area 13 of the cross-bottom 3 enters the deposit area 23, the gas mass flow supplied to the hot gas means 24 is increased from the basic mass flow {dot over (m)}.sub.1 by the pulse mass flow {dot over (m)}.sub.2 to the total mass flow {dot over (m)}.sub.ges. For this purpose, the injector 30 is simply switched on again by the control 34. The total mass flow {dot over (m)}.sub.ges and the internal volume 36 are coordinated such the hot gas reservoir 31 is filled with the hot charge gas, but no hot charge gas leaves the hot gas reservoir 31, while the gas mass flow supplied to the hot gas means 24 corresponds to the basic mass flow m.sub.1 Correspondingly, the hot gas reservoir 31 is filled with hot charge gas during the switching from the basic mass flow {dot over (m)}.sub.1 to the total mass flow {dot over (m)}.sub.ges. The process is now repeated in exactly the same way as with the first inner triangular area 12. Gas with the temperature T.sub.H is discharged from the nozzle 32 or, respectively, the hot gas reservoir 31, and the hot gas reservoir 31 is filled with cold charge gas.

(36) When the second inner triangular area 13 leaves the deposit area 23, the gas mass flow supplied to the gas heater 30 is again reduced from the total mass flow {dot over (m)}.sub.ges to the basic mass flow {dot over (m)}.sub.1, and the hot gas reservoir 31 is charged with hot charge gas, and gas with the temperature T.sub.N is displaced from the hot gas reservoir 31. Correspondingly, gas with the low temperature T.sub.N and the basic mass flow {dot over (m)}.sub.1 leaves the nozzle 32 and gets into the deposit area 23, when the outer triangular areas 41 and 42 are located in the deposit area 23 and when the gas hits the conveyor belt 4 at a distance 38 or, respectively, as soon as the second inner triangular area 13 has passed the deposit area 23.

(37) The gas with the low temperature T.sub.N and the basic mass flow {dot over (m)}.sub.1 is advantageously deviated away from the deposit area 23 and into an environment by a deflecting means, which is not illustrated, for example a rotary valve or a baffle, if the outer triangular areas 41 and 42 are located in the deposit area 23 and the gas would hit the conveyor belt 4 at a distance 38. In this way, it is prevented that heat is introduced into the outer triangular areas 41 and 42, which might cause damage to the fabric.

(38) If a further inner first triangular area 12 of a subsequent cross-bottom 3 reaches the deposit area 23, the above-described process will restart from the beginning.

(39) Since the central area 14 is raised in relation to the inner triangular areas 12 and 13, the central area 14 is arranged closer to the nozzle 32 than the inner triangular areas 12 and 13. Due to the increased temperature T.sub.H and the increased mass flow {dot over (m)}.sub.ges with which the gas is emitted from the nozzle 32 into the inner triangular areas 12 and 13, the same amount of heat is introduced into the inner triangular areas 12 and 13 as into the central area 14, whereby a surface of the cross-bottom 3 is evenly heated and melted.

(40) While a cover sheet 9 is placed on a cross-bottom 3 and heat is introduced into the deposit area 23 via the gas mass flow, the cover sheet 9 is pressed onto the cross-bottom 3 by means of a press cylinder 39, whereby the cross-bottom 3 is welded to the cover sheet 9.

(41) As a result of the uniform heating of the surface of the cross-bottom 3, uniform adhesion of the cover sheets 9 to the cross-bottoms 3 can be achieved. By the hot gas reservoir 31 and the controlled supply of gas to the hot gas means 24, which occurs according to the invention, the thermal heat flow {dot over (Q)}.sub.H can be kept constant, and it is prevented that hot gas has to be released into the environment in an unused state so as to evenly heat the surface of the cross-bottom 3.