GB2490208A - Device and method for manufacturing a can body for an aerosol can - Google Patents

Abstract

The present invention thus relates to a device and to a method in which a can body (11) with cylindrical wall (12) and a neck section (13) of lower diameter can be manu­factured in one working stroke in one working direction (A). The device (10) has a drivable drawing ring (27) used for deep-drawing of a cup from a round, disk-like or plate ­like blank (32) in a first phase of the working stroke. Af­ter completion of this first phase the cup is drawn with the aid of an ironing mandrel (59) into an ironing channel (38) and formed into an ironed workpiece . Fi­nally, a stretch-forming mandrel (58) is moved out of a guide recess (60) of the ironing mandrel (59) and forms the neck section (13) or at least a part thereof in a stretch-drawing phase of the working stroke, in conjunction with a forming depression (48) of a domer (45). With the conclu­sion of the stretch-drawing phase, the working stroke is completed.

Description

Device and method for manufacturing a can body for an aerosol can The present invention relates to a devioe and to a me- thod for manufaoturing a oan body which is used in particu-lar for manufacturing an aerosol can. The can body to be manufactured has a cylindrical wall section adjoined by a neck section with a lower diameter when compared with the cylindrical wall section, where the neck section preferably has a cylindrical end section. This can body is then used as a semi-finished part for the manufacture of an aerosol can.

The manufacture of an aerosol can is subject to con- flicting aims. On the one hand the aerosol cans of differ-ent manufacturers should stand out from each other, which can lead to increased material and cost expenditure, and on the other hand low material consumption and low weight are required for cost reasons and in particular for environmen-tal reasons. In comparison with beverage cans, the required quantities of the aerosol cans are however considerably lower, so that the same economies of scale as with beverage cans cannot be achieved. Complex and expensive manufactur-ing devices that have proven themselves for the manufacture of beverage cans cannot therefore be readily transposed to a device for manufacture of an aerosol can.

US 5 357 779 describes for example a so-called!Tbody maker!! used for manufacturing a can body, where a workpiece with a bottom and an adjoining cylindrical wall is made from a pre-formed cup by ironing. A narrowed section cannot be achieved with this device.

A machine and a method for controlled spin flow form-ing of cans is known from DE 37 83 509 T2. This publication proceeds from a conventional method in which a preformed cup is shaped by ironing, where the bottom of the cup de-creases and the length of the cylindrical wall increases.

Following that, the wall can he provided in a separate de- vice with a neck section and a flange. For example, die-forming, roller spinning or pressure-forming is proposed for shaping of the neck, using a spinning roller rotating along the outer circumference, with the spinning roller in-teracting with an inner member provided inside the can body.

DE 378 35 09 T2 proposes a spin flow forming method that controls the metal flow during forming in order to mi-nimize metal damage.

A method for manufacturing a can body is known from DE 69 711 587 T2, where a cup is first made from a plate-like blank by deep-drawing. Following that the cup is shaped by ironing into an ironed workpiece, and then the circumfe- rence of the ironed workpieoe is calibrated in several in-dividual steps, for which several mold sets are used. Each mold set has a mold and a counter-mold. During this cali- bration of the circumferential surface of the ironed work- piece, an excess thickness of the cylindrical wall is re-tained. Finally, a shaped area is created on the wall by so-called hydroforming or a pressure pad, and can project either inwards as a narrowed section or outwards. With this manufacturing method too, various devices are necessary for different process steps, making manufacture very expensive.

Proceeding from this known prior art, it can be re- garded as a task of the present invention to provide a de- vice and a method for manufacturing a can body, in partiou-lar for aerosol cans, that manage with simple tools and can therefore be used economically even for small quantities.

This task is solved by a device with the features of claim 1 and by a method with the features of claim 12.

The core of the invention is that the can body used for the manufacture of the can, in particular of an aerosol can, is manufactured as a semi-finished part, generally speaking in a single and preferably vertical working stroke with several mandrels. First, a cup is manufactured from a plate-like and preferably circular blank by deep-drawing with the aid of a drawing ring. After deep-drawing of the cup, the drawing ring preferably acts as a hold-down for an ironing mandrel arranged coaxially to the drawing ring, which mandrel is moved in the direction of the working stroke, engages in the cup and draws the latter though an ironing channel. During this phase of the working stroke, an ironed workpiece with a bottom and a cylindrical wall adjoining the bottom is manufactured from the cup. During ironing, the axial length of the wall increases while the wall thickness decreases. This can be performed by ironing rings inside the ironing channel in several individual steps.

Finally, during the last phase of the working stroke and as a result of stretch-forming of the bottom or of a central bottom section of the ironed workpiece, the axial length of the latter is further increased and a neck sec-tion is formed with a diameter smaller than the diameter of the cylindrical wall. To do so, a stretch-forming mandrel is provided which moves relative to the ironing mandrel during the last phase of the working stroke and forms the neck section from the bottom of the ironed workpiece. The stretch-forming mandrel preferably operates here together with a domer which has a forming depression in an extension to the ironing channel. While so doing, the stretch-forming mandrel presses a bottom section of the ironed workpiece into the forming depression of the domer. The ironing mand-rel is here preferably used as a hold-down and interacts with a contact face on the domer.

A can body with a cylindrical wall and an adjoining neck section of lower diameter can thus be manufactured by one movement of the drawing ring, of the ironing mandrel and of the stretch-forming mandrel in a preferably vertical direction and in a single working stroke. The can body is manufactured in a single setup. No workpiece is transported between different machining devices between the forming phases. The forming of the plate-like blank into the can body is achieved by one working stroke in one working di- rection along the longitudinal axis of the device, prefera-bly vertically. The device necessary to do so is of very simple design and hence inexpensive to manufacture. The de-vice can therefore be used economically even for small quantities. Complex tools for manufacturing a narrowed or drawn-in neck section are not necessary. The further processing of the can body into a complete can, in particu-lar into an aerosol can, can then be designed simply and economically: for example, the still closed end of the neck section can be opened by laser cutting or by another cut-ting process, and the open opposite end closed by inserting a circular bottom. Circular bottoms of this type can be manufactured and connected to the cylindrical wall of the can body simply and inexpensively.

In an advantageous embodiment of the device, the iron-ing mandrel has a hollow-cylindrical design and coaxially surrounds the stretch-forming mandrel. The ironing mandrel can be mounted movable relative to the stretch-forming mandrel and can contact the outer surface of the stretch-forming mandrel. The stretch-forming mandrel is located, during ironing to manufacture the ironed workpiece, inside the central recess of the hollow-cylindrical ironing mand-rel. The stretch-forming mandrel is preferably not moved out of the central recess of the ironing mandrel until the neck section has been shaped from the bottom of the ironed The drawing ring is moved by a drawing ring drive unit which can, in its movement mode, control or regulate the position or the movement of the drawing ring. In its force mode, the drawing ring drive unit controls or regulates the force exerted by the drawing ring on the cup. In this way, the drawing ring can be used both for deep-drawing of the cup and as a hold-down during ironing.

In a preferred embodiment, a blocking device is pro- vided on the punch which contains the stretch-forming mand-rel and the ironing mandrel. The blocking device prevents in its blocking position a relative movement between the stretch-forming mandrel and the ironing mandrel during the working stroke. In particular, the blocking device is in the blocking position during ironing to manufacture the ironed workpiece from the cup. This ensures that the iron-ing mandrel is in contact by its end area with the bottom of the cup / workpiece, and that no undesirable deformation of the workpiece occurs.

The blocking device is preferably not switched to its release position until the stretch-forming operation for manufacture of the neck section is completed. The ironing mandrel can here preferably be in contact with a contact surface at the end of the ironing channel and perform the function of a hold-down. Thanks to the continued movement of the punch in the working direction, the stretch-forming mandrel is moved out of the central recess of the ironing mandrel and forms the bottom section / bottom of the ironed workpiece. Here it preferably presses the bottom section into a forming depression of the domer. At the end of the stretch-forming operation by the stretch-forming mandrel, the working stroke in the working direction is ended. The punch drive unit moves the punch with the ironing mandrel and the stretch-forming mandrel back against the working direction. During this return stroke movement, the can body can be stripped from the ironing mandrel.

Advantageous embodiments of the present invention are set forth in the dependent claims and in the description.

The description explains a design example of the device in accordance with the invention and of the method in accor- dance with the invention on the basis of the attached draw-ing. The description confines itself here to substantial features of the invention. The drawing may be referred to additionally and shows in: Figure 1 a design example of a device for manufactur- ing a can body in a schematic view of a longitudinal sec-tion at the start of the working stroke, Figure 2 the device according to Figure 1 after deep-drawing of a cup from a plate-like blank, Figure 3 the device according to Figures 1 and 2 at the end of ironing through an ironing channel, Figure 4 the device according to Figures 1 to 3 dur-ing stretch-forming of the bottom section of the ironed workpiece at the end of the working stroke and Figure 5 the fully manufactured can body in a sche-matic view of a longitudinal section.

Figures 1 to 4 show a preferred design example of a device 10 for manufacturing a can body 11. The can body 11 is shown schematically in Figure 4 in a longitudinal sec-tion and has a cylinder-like wall 12 continued at one end of the can body 11 in a neck section 13. In the area of the neck section 13, the diameter of the can body 11 is smaller than in the area of the cylindrical wall 12. Starting from the cylindrical wall 12, the can body 11 tapers in a first area 13a, so that the outer surface of the can body 11 is curved in the first area 13a. Adjoining the first area 13a, the neck section 13 has a second area 13b with a cylindric-al flange 14 sealed at the closed free end 15 of the can body 11 by a circular wall area 16. On the side opposite the closed free end 15, the can body 11 forms an open end 17 where the opening is limited by the circular rim 18 of the cylindrical wall 12. This can body 11 is used as a semi-finished part for manufacturing an aerosol can. To do so, the can body 11 can be sealed at its open end 17 by a circular bottom and cut open in the area of the flange 14.

The device 10 is shown in Figures 1 to 4 in a heavily schematic form in the manner of a block diagram. Guideways, frames, bearings and the like are not shown. The device 10 in the design example has a drawing ring 26 drivable in a working direction A by a drawing ring drive unit 25. The drawing ring 26 is arranged coaxially to a longitudinal axis L of the device 10. The working direction A is aligned parallel to the longitudinal axis 11.

Coaxially to the drawing ring 26, a hold-down 27, an-nular in accordance with the example, is mounted movable in the working direction A by a hold-down drive unit 28.

Thanks to the through-hole 29 arranged coaxially to the longitudinal axis L and surrounded by the hold-down 27, the drawing ring 26 can be moved by the drawing ring drive unit in the working direction A. The hold-down 27 is used for clamping of a plate-like blank 32 against a support surface 34 on a table 33 immova-bly arranged on a frame. The support surface 34 is aligned substantially at right angles to the longitudinal axis L and in the design example runs in a horizontal plane. The longitudinal axis L and the working direction A extend pre-ferably in the vertical direction.

The support surface 34 forms a ring and encloses the opening of a cylindrical deep-drawing channel 37 in the ta-ble 33 arranged coaxially to the longitudinal axis L. At the end opposite the support surface 34, the deep-drawing channel 37 is continued by a cylindrical ironing channel 38, where the diameter of the ironing channel 38 is smaller than the diameter of the deep-drawing channel 37. As a re-sult, a step 39 with a ring-shaped retaining surface 40 is formed at the transition point between deep-drawing channel 37 and ironing channel 38. The retaining surface 40 extends in a plane parallel to the support surface 34 and substan-tially horizontally in accordance with the example.

The ironing channel 38 is closed at its end opposite the step 39 by a domer 45. The domer 45 is pretensioned against the table 33 by an elastic pretensioning means 46, which can for example be formed by a spring array. The do-mer 45 is thus mounted movable against the force of the pretensioning means 46. In an extension of the ironing channel 38, the domer 45 has on its working side 47 asso-ciated with the ironing channel 38 a forming depression 48.

The forming depression 48 has at the transition point to the working side 47 the same diameter as the ironing chan- nel 38 and has a first depression area 49 in which the di-ameter of the forming depression 48 continuously decreases.

The wall limiting the forming depression 48 in the first depression area 49 is concave in accordance with the exam- ple. Adjoining the first depression area 49, a second de-pression area 50 is provided coaxially to the longitudinal axis L, representing a cylindrical cavity and ending at a bottom 75.

The deep-drawing channel 37, the ironing channel 38 and the forming depression 48 are arranged along the common longitudinal axis L. The device 10 has furthermore a punch 56 movable in the working direction A by a punch drive unit 55. The punch 56 contains a carrier part 57 to which a cylindrical stretch-forming mandrel 58 is arranged along the longitu-dinal axis L. An ironing mandrel 59 is arranged coaxially to the stretch-forming mandrel 58. The ironing mandrel 59 has a hollow-cylindrical form and contacts in the area of its preferably cylindrical guide recess 60 the outer sur-face of the stretch-forming mandrel 58 an. The shape of the end area 59a of the ironing mandrel 59 is matched to the shape of the first depression area 49 of the forming de- pression 48 and, in accordance with the example, is de- signed rimless and in particular convex. The ironing mand-rel 59 is movably mounted along the stretch-forming mandrel 58 and hence along the longitudinal axis L relative to the stretch-forming mandrel 58. It is braced via a force set-ting means 61 on the carrier part 57 of the punch 56. A spring array 62 with one or more helical springs is used as the force setting means 61 in the design example. The car-rier part 57 furthermore has a blocking device 63 which is used to prevent any movement of the ironing mandrel 59 against the working direction A during the working stroke of the punch 56.

In the preferred design example, the blocking device 63 has for that purpose at least one and preferably more slides 64 which can be moved between the carrier part 57 and the ironing mandrel 59 offset to the springs of the spring array 62 or moved out of this intermediate space.

The slides 64 are for that purpose arranged radially mova-ble relative to the longitudinal axis L on the carrier part 57, as illustrated schematically by the arrow P in Figure 1. If the slides 64 are in the intermediate space between the carrier part 57 and the ironing mandrel 59, the latter cannot move against the working direction A and against the spring force of the spring array 62, and compress the spring array 62. The blocking device 63 is then in its blocking position, shown in Figure 1. If the slides 64 are moved out of this intermediate space between the ironing mandrel 59 and the carrier part 57, then the ironing mand- rel 59 can move against the spring force of the spring ar-ray 62 relative to the stretch-forming mandrel 58 and against the working direction A. The blocking device 63 is then in its release position. The slides can be moved in a linear or in a swivel movement.

In an alternative design, the blocking device 63 can have, instead of the movable slides 64, blocking parts swi-velable about the longitudinal axis L and swiveled between a blocking position and a release position by a predeter-mined swivel angle about the longitudinal axis L. In the blocking position, the blocking parts contact the asso-ciated end face of the ironing mandrel 59 and prevent its movement against the working direction A and against the spring force of the spring array 62. In the release posi-tion, recesses are provided in the ironing mandrel 59 in the extension of the blocking parts, in which recesses the blocking parts can engage such that movement of the ironing mandrel 59 against the working direction A is possible. The blocking parts can be designed matching the slides 64, for

example bar-like.

For a better overview, the drive units 25, 28, 55 in Figures 2 to 4 are not shown. In the preferred design exam-ple, each drive unit 25, 28, 55 is made up of an electric motor and preferably a servomotor. These servomotors can each be operated in alternating mode, alternating between two rotary settings, and manage without mechanical move-ment-transmitting elements such as clutches or brakes. The method for manufacturing the can body 11 shown schematical-ly in Figure 5 is now explained on the basis of Figures 1 to 4.

In Figure 1, the blank 32 is placed on the support surface 34. The blank 32 has a disk-like or plate-like form with substantially constant thickness and has a preferably circular form. The hold-down drive unit 28 moves the hold-down 27 in the working direction A and clamps the blank 32 between the hold-down 27 and the support surface 34. The clamping force of the blank 32 is preferably controlled or regulated by the hold-down drive unit 28. In this state, the working stroke in the working direction A begins to form the plate-like blank 32 into the can body 11. To do so, the punch 56 is moved by the punch drive unit 55, and the drawing ring 26 by the drawing ring drive unit 25, to-gether in the working direction A. The drawing ring drive unit 25 is here in movement mode, in which it controls or regulates the position and/or the acceleration and/or the speed of the drawing ring 26 during its movement in the As soon as the drawing ring 26 contacts the blank 32, it begins to draw the latter into the deep-drawing channel 37. The hold-down drive unit 28 here regulates the clamping force or the hold-down foroe of the hold-down 27, so that the blank is drawn from between the hold-down 27 and the support surface 34 and then oompletely into the deep-drawing channel 37, as illustrated in Figure 2. At the end of deep-drawing, the drawing ring 26 has formed the blank 32 into a cup 70 with a bottom 71 and a cylindrical wall section 72. At the end of deep-drawing, the drawing ring 26 presses an annular area of the bottom 71 adjoining the wall section 72 against the retaining surface 40 of the step 39.

This position of the drawing ring 26 can also be referred to as the retaining position or clamping position. As soon as the drawing ring 26 has reached this olamping position, the drawing ring drive unit 25 switches from its movement modo into a foroo mode. In this foroo mode, tho drawing ring drive unit 25 controls or regulates the force with which the drawing ring 26 presses the bottom 71 of the cup against the retaining surfaoe 40. The drawing ring 26 thus praotioally operates as a hold-down for the punch 56.

Following deep-drawing, a further phase of the working stroke begins in the working direction A. The punch 56 is moved further in the working direction A by the punch drive unit 55. The blocking device 63 is in its blocking position and prevents any movement of the ironing mandrel 59 rela- tive to the stretch-forming mandrel 58. Due to the contin- ued movement of the two mandrels 58, 59 in the working di-rection A, the ironing mandrel 59 comes into oontaot with the bottom 71 and draws the oup 70 into the ironing channel 38.

The cup 70 is formed during the joint movement of the ironing mandrel 59 with the stretch-forming mandrel 58 through the ironing channel 38, where the surface area of the bottom 71 decreases while the axial length of the wall section 72 increases and its wall thickness decreases until it finally corresponds to the reguired dimensions of the wall 12 of the can body 11. At the end of ironing, the cup is shaped into an ironed workpiece 73 as illustrated in Figure 3.

Forming of the cup 70 into an ironed workpiece 73 is followed by a final phase of the working stroke in the working direction A. First, the punch 56 with its two man-drels 58, 59 is moved in the working direction A until the ironed workpiece 73 is in contact with the wall of the first area 49 of the forming depression 48. In this posi- tion, the blocking device 63 is switched to its release po-sition. Switching of the blocking device 63 to the release position allows the ironing mandrel 59 to be moved against the working direction A and relative to the stretch-forming mandrel 58. The punch drive unit 55 moves the punch 56 fur-ther in the working direction A. Since the domer 45 presses via the pretensioning means 46 against the ironing mandrel 59, the latter is moved against the spring force of the spring array 62 and relative to the stretch-forming mandrel 58. The force setting means 61 formed by the spring array 62 here determines the clamping or holding-down force with which the ironing mandrel 59 presses the ironed workpiece 73 against the wall of the first depression area 49 in the forming depression 48 of the domer 45. At the same time, the stretch-forming mandrel 58 presses a central bottom section 74 of the ironed workpiece 73 into the second de-pression area 50 of the forming depression 48. The axial length of the ironed workpiece 73 increases here. During this last phase of the working stroke in the working direc-tion A, stretch-forming of the ironed workpiece 73 takes place, with the stretch-forming mandrel 58 and the domer 45 interacting.

Figure 4 shows the final position of the working stroke in the working direction A, where the stretch-forming mandrel 58 has pressed the central bottom section 74 against the bottom 75 of the second area 50 of the form-ing depression 48. The forming of the blank 32 into the can body 11 is completed and the punch drive unit 55 can move the punch 56 against the working direction A back into the initial position. During this return stroke, the can body 11 can be stripped from the punch 56 or from the ironing mandrel 59. For this purpose, stripping means not shown in detail can be moved into contact with the outer surface of the ironing mandrel 59 and can engage the rim 18 of the can body 11 so that the can body 11 is removed as the return stroke continues.

After the return stroke of the three forming mandrels 26, 58 and 59 and of the hold-down 27, the next round disk-like or plate-like blank 32 can be inserted and formed as described above in the next working stroke.

The present invention thus relates to a device and a method in which a can body 11 with cylindrical wall 12 and a neck section 13 of lower diameter can be manufactured in one working stroke and in one working direction A. The de- vice 10 has a drivable drawing ring 27 used for deep-drawing of a cup 70 from a plate-like blank 32 in a first phase of the working stroke. After completion of this first phase, the cup 70 is drawn with the aid of an ironing mand-rel 59 into an ironing channel 38 and formed into an ironed workpiece 73. Finally, a stretch-forming mandrel 58 is moved out of a guide recess 60 of the ironing mandrel 59 and forms the neck section 13 or at least a part thereof in a stretch-drawing phase of the working stroke, in conjunc-tion with a forming depression 48 of a domer 45. With the conclusion of the stretch-drawing phase, the working stroke is completed.

List of reference numbers: Device 11 Can body 12 Wall 13 Neck section 13a First area of the neck section 13b Second area of the neck section 14 Flange Closed free end 16 Wall area 17 Open end 18 Rim Drawing ring drive unit 26 Drawing ring 27 Hold-down 28 Hold-down drive unit 29 Through-hole 32 Blank

33 Table

34 Support surface 37 Deep-drawing channel 38 Ironing channel 39 Step Retaining surface Domer 46 Pretensioning means 47 Working side 48 Forming depression 49 First depression area Second depression area Punch drive unit 56 Punch 57 Carrier part 58 Stretch-forming mandrel 59 Ironing mandrel 59a End area of the ironing mandrel Guide recess 61 Force setting means 62 Spring array 63 Blocking device 64 Slide Cup 71 Bottom 72 Wall section 73 Ironed workpiece 74 Central bottom section Bottom A Working direction L Longitudinal axis p Arrow