EFFICIENT PRODUCTION LINE FOR AEROSOL CANS

Abstract

A production line with processing stations processing products with a production speed in products per unit time, the production line comprising a temporarily discontinuously operating processing station; a production line section connected upstream of the temporarily discontinuously operating processing station; a production line section connected downstream from the temporarily discontinuously operating processing station; a first product buffer arranged between the upstream production line section and the temporarily discontinuously operating processing station; and a second product buffer arranged between the temporarily discontinuously operating processing station and the downstream production line section.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 USC §119 to German Patent Application No. 10 2011 080 769.1 filed on Aug. 10, 2012, which application is hereby incorporated by reference.

TECHNICAL FIELD

The invention relates to a production line with processing stations which process products per unit time with a production speed, wherein the production line includes a processing station operating discontinuously from time to time, a production line section arranged upstream of the processing station and a production line section arranged downstream of the processing station.

BACKGROUND OF THE INVENTION

Production lines of the type recited supra are known in the art and are being used for example when producing and/or processing containers like aerosol cans, beverage cans or tubes.

Typical production speeds of production lines of this type are between 50 and 2500 containers per minute (subsequently designated as cpm), wherein production speeds of greater than 500 cpm are typically used during mass production of beverage cans, production speeds of less than 100 cpm are used in the production of special containers like aluminum tubes. Production lines for producing aerosol cans are configured for a production speed between 100 cpm and 500 cpm, in particular between 150 cpm and 250 cpm.

The containers to be produced are typically combined in so-called batches, wherein a batch defines a number of containers which are processed by a discontinuously operating processing station between two retrofits of the processing station. In aerosol can production, the batch size is typically 10000 to 1000000 containers.

For the duration of a retrofit wherein the retrofit is for example a décor change of a decoration station, besides the processing station itself standing still that needs to be retrofitted, also the upstream or downstream production line section of the processing station stands still.

In order to compensate the productivity reduction caused by a standstill of this type, a processing station that operates discontinuously from time to time and the upstream or downstream production line section of the processing station are configured for a production speed which is typically significantly higher than a production speed of a production line without retrofit requirement.

SUMMARY OF THE INVENTION

The invention is based on the finding that the cost for a production line is disproportionally high in the prior art, since the entire production line is configured for a higher production speed.

It is the object of the present invention to provide a production line with a processing station that operates discontinuously from time to time, wherein the production line achieves high productivity with lowest possible complexity. This object is achieved by a production line in that a first product buffer is arranged between the upstream production line section and the processing station that temporarily operates in a discontinuous manner and a second product buffer is provided between the processing station that temporarily operates in a discontinuous manner and the downstream production line section and the production line is connected with a control which controls the production line so that the temporarily discontinuously operating processing station after a production interruption of the processing station operates with increased production speed relative to the upstream and the downstream production line section until the initially filled first product buffer is depleted down to a predetermined amount and/or the initially depleted second product buffer is filled to a predetermined amount.

In the production line according to the invention, the upstream production line section and the downstream production line section in case of a production interruption of the temporarily discontinuously operating processing station can continue to produce until the initially depleted first product buffer is filled to a predetermined amount and/or the initially filled second production buffer is depleted to a predetermined amount, so that the upstream production line section and the downstream production line section can have a lower production speed than comparable prior art production line sections without the production speed of the entire production line being lower.

The solution according to the invention includes the finding that prior production improving measures are directed to increasing production speed in itself. It was also found that a higher production speed comes with a higher scrap rate which in turn causes an effective productivity reduction. A significant quality increase of the products produced is achieved in that the maximum production speed is only increased in one processing station, thus the processing station temporarily operating in a discontinuous manner and the maximum production speeds of the production line sections that are connected upstream or downstream are limited.

Discontinuous manner in this context means that a processing station operating in a discontinuous manner temporarily does temporarily not operate with its actual production speed but that its production is temporarily interrupted, wherein the interruption does not have to coincide with an abrupt change of the production speed, for example between standstill (for a production interruption) and increased production speed. A discontinuous operating mode rather means that a transition of the production speed from standstill to another production speed can be provided without speed leaps.

The solution according to the invention can be supplemented with additional advantageous embodiments. Some of the embodiments are subsequently described.

In a particularly preferred embodiment, the temporarily discontinuously operating processing station is a deco station for decorating a product with a respectively replaceable decoration. Replacing the decoration requires retrofit time which causes a respective production interruption of the deco station. The production buffers have a buffer capacity which are respectively adjusted to the production speed of the upstream production line section or the downstream production line section so that a filling time used with this production speed for filling the first product buffer and/or an emptying time used for emptying the second product buffer is greater than or equal to the retrofit time.

In order to facilitate an optimum loading of the production line, the control can control the upstream production line section and the downstream production line section so that the upstream production line section and the downstream production line section operate with their maximum possible production speed as long as the number of products to be processed in a batch is greater or equal to the product of the emptying time of the first product buffer related to this maximum production speed and the maximum possible production speed of the upstream production line section.

As long as the number of the products to be processed in a batch is less than the product of the emptying time of the first product buffer related to the maximum production speed of the upstream production line section and the downstream production line section and the maximum possible production speed of the upstream production line section, the control can cause the upstream production line section and the downstream production line section to operate with a reduced production speed relative to its maximum possible production speed. This facilitates a reliable production in particular for small batch sizes.

In order to be configured in an optimum manner for the requirements of aerosol can production, the upstream production line section and the downstream production line section in an advantageous embodiment are configured for a maximum production speed of 200 products per minute. In an alternative embodiment, the temporarily discontinuously operating processing station is configured for a maximum production speed of 250 products per minute. In another advantageous embodiment, the upstream production line section and the downstream production line section are configured for a maximum production speed of 250 products per minute.

For a particularly advantageous operation of the production line, the maximum production speed of the upstream production line section and of the downstream production line section can be higher than 150 products per minute and lower than 300 products per minute. In order to facilitate particularly uniform filling and emptying of the product buffers, the control can control the upstream production line and the downstream production line so that the production speed of the upstream production line and the production speed of the downstream production line are identical.

In a particularly advantageous embodiment, the upstream production line section includes an extrusion press and the downstream production line section includes a fold over station. Since stations of this type are very expensive, limiting their maximum production speed is particularly advantageous for the cost of the entire production line.

The deco station can include a coating unit, a decoration unit, a lacquering unit and the associated drying ovens. In an alternative embodiment, the temporarily discontinuously operating processing station is configured as a decoration drying oven.

In another advantageous embodiment, the upstream production line section includes a drawing device and/or a stretching device. The downstream production line section can include a combined drawing-stretching device. In a particularly advantageous embodiment, the drawing device is a “cupper”. The stretching device can be a “body maker”.

The object of the invention is achieved through a method for operating a production line, wherein the production line includes a temporarily discontinuously operating processing station, a production line section connected upstream of the temporarily discontinuously operating processing station, a production line section connected downstream of the temporarily discontinuously operating processing station, a first product buffer arranged between the upstream production line section and the temporarily discontinuously operating processing station and a second product buffer arranged between the temporarily discontinuously operating processing station and the downstream production line section.

The method provides that the temporarily discontinuously operating processing station is operated with an increased production speed relative to the upstream and the downstream production line section after a production interruption of the processing station until the initially filled first product buffer is emptied to a predetermined amount and/or the initially emptied second product buffer is filled to a predetermined amount.

The upstream production line section and the downstream production line section can continue to produce in case of a production interruption of the temporarily discontinuously operating processing station until the initially emptied first product buffer is filled to a predetermined amount and/or until the initially filled second product buffer is depleted to a predetermined amount.

In a particularly advantageous embodiment, the method provides retrofitting the temporarily discontinuously operating processing station, wherein the processing station is a deco station for decorating a product with a respectively replaceable decoration and the retrofitting means a replacement of the decoration with a retrofit time which causes a respective production interruption of the deco station. The production buffers have a buffer capacity which is respectively adapted to the production speed of the upstream production line section and/or of the downstream production line section so that a filling time that is used at this production speed for filling the first product buffer and an emptying time that is used at that production speed for emptying the second product buffer is great than or equal to the retrofit time.

In an advantageous embodiment, the upstream production line section and the downstream production line section are operated with their maximum production speed as long as the number of the products to be processed in a batch is greater than or equal to the product of the emptying time of the first buffer related to this maximum production speed and the maximum possible production speed of the upstream production line section.

In a particularly advantageous embodiment, the production speed of the upstream production line section, and of the downstream production line section, are reduced with respect to their maximum possible production speed.

BRIEF DESCRIPTION OF THE DRAWINGS

Subsequently the invention is described with reference to embodiments illustrated in drawing figures. The different features in the drawing figures like in the embodiments described supra are randomly combinable with one another, wherein:

FIG. 1 illustrates a schematic depiction of an exemplary embodiment of a production line according to the invention in a stationary production condition directly before a retrofit starts;

FIG. 2 illustrates a schematic depiction of an exemplary embodiment of the production line of FIG. 1 in a production condition directly after a beginning of a retrofit;

FIG. 3 illustrates a schematic illustration of an exemplary embodiment of the production line according to the invention according to FIG. 1 in a production condition during retrofit;

FIG. 4 illustrates a schematic depiction of an exemplary embodiment of the production line according to the invention according to FIG. 1 in a production condition directly before an end of the retrofit;

FIG. 5 illustrates a schematic depiction of an exemplary configuration of the production line according to the invention according to FIG. 1 in a production condition directly after the end of the retrofit;

FIG. 6 illustrates a schematic depiction of an exemplary embodiment of the production line according to the invention according to FIG. 1 in a production condition substantially after the end of the retrofit;

FIG. 7 illustrates a schematic depiction of an exemplary embodiment of the production line according to the invention according to FIG. 1 in a production condition directly before reaching a stationary production condition;

FIG. 8 illustrates an exemplary embodiment of the production line according to the invention according to FIG. 1 in a stationary production condition; and

FIG. 9 is a chart that illustrates the required difference in production speeds according to the invention.

DETAILED DESCRIPTION

An assembly line 100 in FIGS. 1 through 8 includes a temporarily discontinuously operating processing station 1 with a production speed v1. The temporarily discontinuously operating processing station 1 has a production line section 2 connected upstream and a production line section 3 connected downstream. The production line section 2 operates with a production speed v2, the production line section 3 operates with a production speed v3.

Between the upstream production line section 2 and the temporarily discontinuously operating processing station 1, a first product buffer 4 with a buffer level p4 is arranged between the temporarily discontinuously operating processing station 1 and the downstream production line section 3 a second product buffer 5 with a buffer level p5 is arranged. A transfer of the products to be processed from the first product buffer 4 to the processing station 1 is provided with a transfer speed v6, a transfer of the process products from the processing station 1 to the product buffer 4 is provided with a transfer speed v7. The change of the buffer level p4 per minute is indicated as v4, the change of the buffer level p5 per minute is designated as v5. A positive prefix of v4 or v5 indicates an increasing buffer level, a negative prefix indicates a decreasing buffer level.

With reference to the configuration of the production lines 100 described in FIGS. 1 through 6, a retrofit time T of 30 minutes is defined. The upstream production line section 2 and the downstream production line section 3 are configured for a maximum production speed of 200 cpm, the temporarily discontinuously operating processing station is configured for a maximum production speed of 250 cpm. The upstream production line section 2 and the downstream production line section 3 are continuously operated with their maximum production speeds of 200 cpm.

During a retrofit of the temporarily discontinuously operating processing station 1, the upstream production line section 2 and the downstream production line section 3 continue to operate with their maximum production speed of 200 cpm, thus they process a number of 6,000 containers respectively during the retrofit time of 30 minutes (200 cpm×30 min.). In order to maintain a continuous production, therefore, a buffer size of 6,000 containers is required for the product buffers 4 and 5. After the retrofit is completed, the product buffer 4 has grown to 6,000 containers, the product buffer 5 is emptied.

The number of 6,000 containers corresponds to the amount to which the product buffer 4 or the product buffer 5 are filled, the number of 0 containers corresponds to the predetermined amount to which the product buffer 4 or the product buffer 5 are depleted. The buffer capacity corresponds to 6,000 containers.

For the retrofit required for the next batch, the buffer level p5 has to be reduced to its original amount of p5=6,000, the buffer level p4 has to be reduced to its original amount of p4=20. Since the temporarily discontinuously operating processing station 1 is configured for a maximum production speed of 250 cpm and thus exceeds the production speed of the upstream production line section 2 or the downstream production line section 3 by 3 to 50 cpm, this yields a time frame of 120 minutes (6,000/(250 cpm-50 cpm)) for completely loading the product buffer 5 or unloading the product buffer 4.

In the time frame of 120 minutes, the upstream production line section 2 and the downstream production line section 3 of 24,000 containers (120 minutes×200 cpm) is run through. This number of 24,000 containers thus represents a maximum batch size B up to which a continuous operation of the upstream production line section 2 and the downstream production line section 3 is feasible.

These definitions refer to the instant embodiment and do not represent a general limitation. Furthermore, it is clear to a person skilled in the art that the defined values are not maintained mathematically exact in production reality, they rather are subject to normal technical variations and other production technique considerations.

FIG. 1 illustrates the production line in a stationary production condition, the stationary mode. The entire production line 100 operates with a uniform production speed of 200 cpm (v1=v2=v3=v6=v7=200 cpm). The product buffer 4 is in empty condition (p4=0), whereas 6,000 containers are included by the second product buffer 5 (p5=6,000).

FIGS. 2 through 4 illustrate the production line during retrofit, the retrofit mode. During this time, the temporarily discontinuously operating processing station 1 stands still (v1=0 cpm), a transfer of products from the first product buffer 4 to the processing station 1 does not occur and a transfer of products from the processing station 1 to the product buffer 4, this means the transfer speed v7 or v6 are 0 cpm. The upstream production line section 2 and the downstream production line section 3 operate with a production speed of 200 cpm, wherein these production line sections process a number of 6,000 containers respectively (200 cpm×30 minutes) during the retrofit time period. This number determines the buffer requirement for maintaining a continuous production.

When the retrofit mode starts (FIG. 2), the buffer level p4 of the product buffer 4 increases at 200 cpm, the buffer level p5 of the product buffer 5 decreases with 200 cpm. After a retrofit time of 5 minutes, the product buffer 4 includes 1,000 containers (p4=1,000), the product buffer 5 has a level of 5,000 containers (p5=5,000).

During the retrofit mode (FIG. 3) after 15 minutes, the product buffer 4 includes 3,000 containers (p4=3,000), the product buffer 5 also has a level of 3,000 containers (p5=3,000).

Directly before an end of the retrofit mode (FIG. 4), after 28 minutes, the product buffer 4 includes 5,600 containers (p4=5,600), the product buffer 5 has a level of 400 containers (p5=400).

At an end of the retrofit mode after 30 minutes, the product buffer 4 includes 6,000 containers (p4=6,000), the product buffer 5 is empty (p5=0).

FIGS. 5 through 7 illustrate the production line during filling the product buffer 4, the refill mode. In refill mode which comes directly after the retrofit mode, the temporarily discontinuously operating processing station 1 operates with an increased production speed (v1=250 cpm). A transfer of products from the first product buffer 4 to the processing station 1 and a transfer of product from the processing station 1 to the product buffer 4 is accordingly provided respectively with an increased transfer speed, this means the transfer speeds v7 or v6 are 250 cpm respectively. The upstream production line section 2 and the downstream production line section 3 continue to operate with the production speed of 200 cpm. For the product buffer, this yields a net of −50 cpm (v2−v6), this means the buffer level p4 decreases, the buffer level p5 increases by 50 cpm (v7−v3), this means the buffer level p4 increases. Since the buffer level p5 has to be reduced to its original amount of p5=6,000, this yields a duration of the filling mode of 120 minutes (6,000/50 cpm).

Five minutes after the refill mode begins (FIG. 5), the product buffer 5 includes 250 containers (p5=250), the product buffer 4 has a level of 5,750 containers (p4=5,750).

During the refill mode (FIG. 6), this means 60 minutes after the refill mode begins, the product buffer 5 includes 3,000 containers (p5=3,000), the product buffer 4 also includes a level of 3,000 containers (p4=3,000).

Directly before an end of the refill mode (FIG. 7), this means 110 minutes after the refill mode begins, the product buffer 5 includes 5,500 containers (p5=5,500), the product buffer 4 has a level of 500 containers (p4=500).

When the refill mode ends after 120 minutes, the product buffer 5 is completely filled (p5=6,000), the product buffer 4 does not include any more containers (p4=0).

FIG. 8 in turn illustrates a production line 100 in a stationary production condition which follows directly after the refill mode described with reference to FIGS. 5 through 7. The entire production line 100 operates with uniform production speeds of 200 cpm (v1=v2=v3=v6=v7=200 cpm). The product buffer 4 is in empty condition (p4=0), whereas 6,000 containers are included in the second product buffer 5 (p5=6,000).

The subsequent tables summarize parameters for the preceding embodiments.

Reference
Numeral/Production	Stationary Mode	Retrofit Mode	Refill Mode
Condition	(FIG. 1, FIG. 8)	(FIG. 2-FIG. 4)	(FIG. 5-FIG. 7)
p4 (c = Container)	0	0-6000	6000-0
v4 (cpm)	0	200	−50
p5 (c = Container)	600	6000-0	0-6000
v5 (cpm)	0	−200	50
v6 (cpm)	200	0	250
v7 (cpm)	200	0	250
v1 (cpm)	200	0	250
v2 (cpm)	200	200	200
v3 (cpm)	200	200	200

In the embodiment described supra, 24,000 containers (120 minutes×200 cpm) are respectively processed by the upstream production line section 2 and the downstream production line section 3 within 120 minutes which corresponds to the time period for completely loading the product buffer 5 or unloading the product buffer 4. This means that the entire production line processes 24,000 containers—one batch—in these 120 minutes. The number of 24,000 containers which represents a typical batch size during aerosol production by the same token represents a minimum batch size up to which a continuous operation of the upstream production line section 2 and the downstream production line section 3 is possible at its maximum production speed of 200 cpm.

The design parameters used for the preceding configuration can be determined in a general manner so that they go beyond the particular embodiment.

Reciting another embodiment, depending on the batch size to be processed and the retrofit time, the upstream production line section 2 and the downstream production line section 3, for example, can have a maximum production speed of 150 cpm and the temporarily discontinuously operating processing station 1 can have an increased production speed of 200 cpm (150/200 operating mode). Additional operating modes are for example 150/180, 250/300 or 250/350.

FIG. 9 illustrates the required difference in production speeds, this means the amount by which the production speed of the temporarily discontinuously operating processing station after a production interruption of this processing station has to exceed the production speed of the upstream and downstream production line sections in order to facilitate a continuous production for the entire production line as a function of the batch size and the respective retrofit time.

FIG. 9 is based on the subsequent general formula according to which the first and the second product buffer have the same buffer capacity and the temporarily upstream connected production line section and the downstream production line section have the same production speed:

Difference of production speeds=retrofit time×(production speed of the production line section)²/batch size, wherein batch size=emptying time of product buffer*production speed of the upstream production line section.

Emptying time of product buffer=buffer capacity of product buffer/(increased production speed of the temporarily discontinuously operating processing station−production speed of the upstream production line section).

Buffer capacity of the product buffer=retrofit time×production speed of upstream production line section.

Claims

1. A production line with processing stations processing products with a production speed in products per unit time, the production line comprising: a temporarily discontinuously operating processing station;a production line section connected upstream of the temporarily discontinuously operating processing station;a production line section connected downstream from the temporarily discontinuously operating processing station;a first product buffer arranged between the upstream production line section and the temporarily discontinuously operating processing station; anda second product buffer arranged between the temporarily discontinuously operating processing station and the downstream production line section,wherein the production line is connected with a control controlling the production line,wherein the temporarily discontinuously operating processing station operates with an increased production speed that is increased relative to the upstream production line section and the downstream production line section after a production interruption of the temporarily discontinuously operating processing station until the initially filled first product buffer is emptied to a predetermined level and/or the initially emptied second product buffer is filled to a predetermined level, andwherein the upstream production line section and the downstream production line section can continue to produce in case of a production interruption of the temporarily discontinuously operating processing station until the initially emptied first product buffer is filled to a predetermined level and/or the initially filled second product buffer is emptied to a predetermined level.

2. The production line according to claim 1, wherein the temporarily discontinuously operating processing station is a deco station for decorating a product with a respectively replaceable decoration, wherein replacing the decoration requires a retrofit time which causes a respective production interruption of the deco station, andwherein the production buffers have a buffer capacity which is respectively adjusted to the production speed of the respective upstream production line section and the respective downstream production line section, so that a filling time provided at this production speed for filling the first product buffer and/or an emptying time provided for emptying the second product buffer is greater or equal to the retrofit time.

3. The production line according to claim 1, wherein the control controls the upstream production line section and the downstream production line section so thatthe upstream production line section and the downstream production line section operate at their maximum possible production speeds if the number of products to be processed in a batch is greater or equal to the product of the emptying time of the first product buffer related to this maximum production speed and the maximum possible production speed of the upstream production line section, andif this condition does not apply,the upstream production line section and the downstream production line section operate with a production speed that is reduced relative to their maximum possible production speed.

4. The production line according to claim 1, wherein the upstream production line section and the downstream production line section are configured for a maximum production speed of 200 products per minute.

5. The production line according to claim 1, wherein the upstream production line section and the downstream production line section are configured for a maximum production speed of 250 products per minute.

6. The production line according to claim 1, wherein the control controls the upstream production line section and the downstream production line section so that the production speed of the upstream production line section and the production speed of the downstream production line section are equal.

7. The production line according to claim 1, wherein the upstream production line section includes an extrusion press and the downstream production line section includes a folding station.

8. The production line according to claim 1, wherein the upstream production line section includes a drawing device and/or a stretching device or a combined drawing—stretching device.

9. A method for operating a production line including a temporarily discontinuously operating processing station,a production line section connected upstream of the temporarily discontinuously operating processing station,a production line section connected downstream from the temporarily discontinuously operating processing station,a first product buffer arranged between the upstream production line section and the temporarily discontinuously operating processing station, anda second product buffer arranged between the temporarily discontinuously operating processing station and the downstream production line section,comprising:operating the temporarily discontinuously operating processing station with an increased production speed that is increased relative to the upstream production line section and the downstream production line section after a production interruption of the temporarily discontinuously operating processing station until the initially filled first product buffer is emptied to a predetermined level and/or the initially emptied second product buffer is filled to a predetermined level,wherein the upstream production line section and the downstream production line section can continue to produce in case of a production interruption of the temporarily discontinuously operating processing station until the initially emptied first product buffer is filled to a predetermined level and/or the initially filled second product buffer is emptied to a predetermined level.

10. The method according to claim 9, further comprising: retrofitting the temporarily discontinuously operating processing station,wherein the temporarily discontinuously operating processing station is a deco station for decorating a product with a respectively replaceable decoration, wherein replacing the decoration requires a retrofit time which causes a respective production interruption of the deco station, andwherein the production buffers have a buffer capacity which is respectively adjusted to the production speed of the respective upstream production line section and the respective downstream production line section, so that a filling time provided at this production speed for filling the first product buffer and/or an emptying time provided for emptying the second product buffer is greater or equal to the retrofit time.

11. The method according to claim 9, further comprising: operating the upstream production line section and the downstream production line section at their maximum possible production speeds if the number of products to be processed in a batch is greater or equal to the product of the emptying time of the first product buffer related to this maximum production speed and the maximum possible production speed of the upstream production line section, andif this condition does not apply,