EP0019646B1 - Apparatus for closing boxes under vacuum with a lid - Google Patents

Abstract

1. Apparatus for the vacuum sealing of cans (7, 7'), comprising a cover (8, 8'), the apparatus having a plate (13, 33) which can be moved upwards by means of a lifting device towards a fixed evacuatable bell (14, 36) and which serves to receive a can (7, 7') already provided with a loosely mounted cover (8, 8'), there being provided a device for lifting the cover (8, 8') clear of the can (7, 7'), characterised in that the device for lifting the cover (8, 8') clear of the can (7, 7') comprises an adjusting piston (20) which can be subjected to a pressure medium and which is guided in an adjusting cylinder (18), and that reducers or reducing adapters (52, 53), which are adapted to different can sizes, can be detachably fitted or fixed on this adjusting piston (20), on the one hand, and on the inner wall of the bell (14), on the other hand.

Description

The invention relates to a device for vacuum sealing cans with a lid, with a plate movable by means of a lifting device from below against a stationary, evacuable bell, for receiving a plate already provided with a loosely placed lid, a device for lifting the Lid of the can is provided.

Such a device is known from DE-A-2 636 003, in which a lifting device is provided, to which a lifting plate is attached. This lifting plate is assigned a closure plate which can be displaced relative to it within limits and which can be sealed against the lower edge of the vacuum bell. In the upper area of the vacuum bell, a device consisting of a plate with a permanent magnet for lifting the lid from the can is elastically displaceably mounted. The lifting device conveys the lifting plate with the can until the cover adheres to the permanent magnet. The lifting plate with the can is then slightly lowered again, but the vacuum bell remains tightly closed. This is followed by evacuation and, if necessary, partial gassing with protective gas. When this is complete, the lifting plate with the can is raised again until the lid rests on the can. The can can then be pushed up further, at the same time pressing the edge of the lid. The vacuum chamber in the vacuum bell is then ventilated again; the lifting plate with the closed box can be moved down again. This device has proven itself extremely well as a semi-automatic device; on the one hand, it is not suitable for extremely high outputs and, on the other hand, it is not suitable for use with differently sized cans.

From DE-A 2 317 517 a device for closing cans, each with a lid under vacuum, is known which has a vacuum space which can be moved vertically by means of two lifting devices relative to one another into a closed position and from one another into an open position of the vacuum space upper or lower vacuum bell is formed. In addition to the two lifting devices, a third drive is provided, by means of which a pressure plate of a closing device can be actuated. The procedure is such that a lid provided with a lid is placed on a lower plate-like receptacle after lowering the lower vacuum bell and then the lower vacuum bell is moved up and the upper vacuum bell is lowered until the vacuum chamber is closed. The pressure plate provided with a permanent magnet or the like is then moved against the cover and then moved back, the cover adhering to the pressure plate. The vacuum chamber is then evacuated and the lid is then pressed onto the can using the pressure plate. Then the vacuum chamber is ventilated again and the two vacuum bells are moved downwards and upwards. This known device works well in principle; however, it has the disadvantage that considerable effort is required for the three lifting devices and the circuits required to control them. In addition, this device is not suitable for converting to cans of different sizes with little effort.

The invention is therefore based on the object of developing a device according to the preamble of patent claim 1 in such a way that cans of different sizes can also be sealed on it without the workflow of the device having to be changed.

This object is achieved according to the invention by the features of the characterizing part of patent claim 1. The configuration according to the invention means that the individual work steps and the lifting heights of the lifting devices do not have to be changed if cans of different sizes, for example 2.5 kg cans and 1 kg cans, are to be sealed.

The measures according to claim 2, namely the separation of evacuating and possibly fumigation on the one hand and closing on the other hand, additionally achieve that lifting devices with a relatively large lifting height and low lifting force, i.e. correspondingly high lifting speed, can be used in the vacuum station, while in the closing station Lifting devices with a low lifting height but a very high lifting force and consequently a correspondingly low lifting speed can be used. It is therefore possible to achieve approximately the same cycle times for the vacuum station on the one hand and the closing station on the other hand, which in turn also contributes to increasing the working speed.

The measures according to claim 3 ensure that the closing station can be adapted to different cover diameters within predetermined tolerance limits. Such slight fluctuations in the lid diameter occur from lot to lot. However, the measures according to claim 3 ensure that even with such different lid diameters, a uniformly firm and secure closing of the can is achieved.

A completely uniform closing of the cans by precisely centering the lid and the can with one another is achieved by the measures according to claim 4.

The measures according to claim 5 already ensure that the lid when evacuating and possibly fumigating the cans and can are assigned to one another as precisely as possible.

• Fig. 1 eine vertikale Längsansicht einer Vorrichtung gemäss der Erfindung in stark schematisierter Darstellung,
• Fig. 2 eine Entgasungskammer der Vorrichtung nach Fig. 1,
• Fig. 3 ein Verschliessaggregat der Vorrichtung nach Fig. 1,
• Fig. 4 eine Entgasungskammer entsprechend der Darstellung in Fig. 2 mit eingesetzten Reduzierstücken und
• Fig. 5 ein Verschliessaggregat entsprechend der Darstellung in Fig. 3 mit eingesetzten Reduzierstücken.

Further advantages and features of the invention result from the description of an exemplary embodiment with reference to the drawing. The drawing shows:

• 1 is a vertical longitudinal view of a device according to the invention in a highly schematic representation,
• 2 shows a degassing chamber of the device according to FIG. 1,
• 3 shows a closing unit of the device according to FIG. 1,
• Fig. 4 shows a degassing chamber as shown in Fig. 2 with reducers and
• Fig. 5 shows a capping unit as shown in Fig. 3 with reducers used.

The device shown in the drawing has a degassing station 1 and a closing station 2. These stations 1, 2 are mounted on identical frames 3, 4 arranged directly next to one another. A conveyor track 5 is provided, which, viewed in the direction of conveyance 6, viewed from cans 7, begins in front of the degassing station 1, through it and through the downstream sealing station 2. On this conveyor track 5, cans 7 are conveyed in cycles with conveyor devices (not shown in detail) and fed to the stations 1, 2. Two degassing devices are arranged in the degassing station 1 shown in the drawing, and two closing devices are arranged in the closing station 2, so that two cans 7 can be degassed or closed at the same time. The cans 7 to be used here are known, for example, from DE-OS 2 263 362. In the filled state, with the lid 8 already loosely placed, they are first fed to the degassing station 1 and then to the closing station 2. Roughly speaking, each degassing device consists of a lifting device 9 and a degassing chamber 10. Each lifting device 9 consists of a pneumatically actuated working cylinder 11 attached to the frame 3 below the conveyor track 5, to the upwardly projecting piston rod 12 of which a lifting plate 13 is attached. In the lower end position of the lifting plate 13 shown on the right in FIG. 1, it lies flush with the conveyor track 5, so that a can 7 can be pushed onto it without further ado. The degassing chamber 10 lies coaxially with the lifting device 9 above it. It has a downwardly open, approximately cylindrical bell 14, which can be closed in a gas-tight manner from the lifting plate 13 in its upper end position, for which purpose the lifting plate 13 is provided in the region of its outer circumference with an annular seal 15, which in this position against a corresponding one Sealing surface 16 is pressed at the lower edge of the bell 14. This position of the lifting plate 13 in its upper end position is shown in FIG. 1 for the left degassing device of the degassing station 1.

The bell 14 is closed at the top by a gas-tight, for example welded, annular cover plate 17, to which a bushing serving as an actuating cylinder 18 is screwed coaxially. This actuating cylinder 18 is in turn attached to a bracket 19 of the frame 3.

In the actuating cylinder 18, an actuating piston 20 is slidably arranged coaxially with the degassing device. It carries at its lower end a concentrically arranged permanent magnet 21 and approximately flush with it a retaining ring 22. Above the actuating piston 20, the actuating cylinder 18 is closed by means of a cylinder end cover 23 screwed on and sealed from above, through which a return rod 24 extends, which extends with it lower end is screwed into the adjusting piston 20. The return rod 24 penetrates a package of springs 25 resting on the top of the cylinder end cover 23, namely disc springs, on which a stop 26 designed as a downwardly open bushing rests, which is screwed onto the return rod 24 from above, thereby preloading the Springs 25 is adjustable. Through the cylinder end cover 23, a channel 27 for the supply or discharge of pressure medium, generally compressed air, opens into a working space 28 of the actuating cylinder 18, specifically between the cylinder end cover 23 and the actuating piston 20. The bell 14 is connected to a connection 29 provided for evacuating and gassing the degassing chamber 10. In the upper area, the inner wall of the bell 14 is provided with a centering surface 30 which tapers conically upwards.

A closing device has a pneumatically actuated lifting cylinder 31, which is attached to the frame 4 below the conveyor track 5 and on whose piston rod 32 which is led out upwards is attached a lifting plate 33 which is the same as the lifting plate 13. A closing unit 35 is arranged coaxially with this lifting device 34 as part of the closing device. The closing assembly 35 has a closing bell 36 which is open at the bottom and which has an upwardly tapering, frustoconical pressing surface 37. The closing bell 36, which is closed at the top by a cover plate 38, is likewise attached to a bracket 40 of the frame 4 via a coaxially arranged bushing serving as an actuating cylinder 39. An actuating piston 41 is arranged in the actuating cylinder 39, and a stop ring 42 is screwed onto its lower end. This stop ring 42 has a circumferential centering collar 43 in its lower outer region.

This actuating cylinder 39 is also closed at the top by a screwed-on cylinder end cover 44, through which a channel 45 for supplying or discharging a pressure medium, such as compressed air, into a working space 46 of the actuating cylinder 39 between the top of the actuating piston 41 and the underside of the cylinder end cover 44 is arranged. In the waiter On the side of the actuating piston 41, a limiting rod 47 penetrating the working space 46 and the cylinder end cover 44 is screwed, which is provided at its outer end with a pot-shaped stop 48 which is adjustable in length on the limiting rod 47. This stop 48 is assigned a stop sleeve 49 screwed into the cylinder cover 44 and penetrating it, which has a stop surface 50 adjacent to the stop 48. In addition, the opposite boundary surface 51 is assigned to the actuating piston 41. The upper end position of the actuating piston 41 is fixed by correspondingly screwing in or unscrewing the stop sleeve 49 into or out of the cylinder cover 44. The lower end position of the actuating piston 41 is fixed by appropriately screwing the stop 48 onto the limiting rod 47.

As can be seen from FIG. 4, a reducer 52, designed as a plate, can be screwed onto the underside of the holding ring 22 of the degassing chamber 10 to change over to cans 7 'of lesser height, and a permanent magnet 21' is concentrically attached to the underside thereof. Furthermore, an approximately cylindrical ring-shaped reducing piece 53 can be introduced into the bell 14 for adaptation to cans 7 'with a smaller diameter, which reducer is releasably locked to the bell 14 by means of resilient ball closures 54. This reducer 53 likewise has a centering surface 30 'which tapers conically upwards in its upper region adjacent to the underside of the reducer 52. It is also provided with degassing openings 55, which are connected to the connection 29 via an annular channel 56 screwed into the outer surface of the reducer 53.

From Fig. 5 it can be seen how to adapt to the cans 7 'of smaller height and smaller diameter on the stop ring, a reducing ring 57 which extends this downward, as it were. Furthermore, a reducing closure bell 58 is screwed onto the underside of the cover plate 38, which also has a pressure surface 37 ′ that tapers conically upwards. The reducing ring 57 is also provided on its underside with a centering collar 43 '.

• Zwei gefüllte und bereits mit einem lose aufgelegten Deckel 8 versehene Dosen 7 werden in die Entgasungsstation 1 eingefahren und auf die beiden Hubteller 13 der Hubeinrichtungen 9 gebracht. Die Arbeitszylinder 11 werden mit Druckluft beaufschlagt, woraufhin die Kolbenstange 12 mitsamt Hubteller 13 und der auf ihr ruhenden Dose 7 nach oben verfährt, bis der Hubteller 13 von unten gegen die Glocke 14 unter gleichzeitiger Abdichtung des Vakuumraums 59 in der Glocke 14 fährt. Aus der Zeichnung ergibt sich, dass der Hubweg des Arbeitszylinders 11 mit Kolbenstange 12 etwas grösser sein muss, als es der Höhe der Dose 7 entspricht. Der Hubweg ist also verhältnismässig gross. Andererseits ist die erforderliche Hubkraft relativ gering. Aus diesem Grunde kann der Arbeitszylinder 11 jeweils verhältnismässig schlank ausgebildet sein.

The device works as follows:

• Two filled cans 7, already provided with a loosely placed cover 8, are moved into the degassing station 1 and brought onto the two lifting plates 13 of the lifting devices 9. The working cylinders 11 are pressurized with compressed air, whereupon the piston rod 12 together with the lifting plate 13 and the can 7 resting on it moves upwards until the lifting plate 13 moves from below against the bell 14 while simultaneously sealing the vacuum chamber 59 in the bell 14. It can be seen from the drawing that the stroke of the working cylinder 11 with the piston rod 12 must be somewhat larger than the height of the can 7. The stroke is therefore relatively long. On the other hand, the required lifting force is relatively low. For this reason, the working cylinder 11 can be made relatively slim.

When the can 7 provided with a cover 8 is moved into the vacuum space 59 of the degassing chamber 10, the actuating piston 20 with the retaining ring 21 and the permanent magnet 21 is in its lower position, which is caused by the contact of the pot-shaped stop 26 on the top of the cylinder end cover 23 is determined. This position of the actuating piston 20 is achieved in that the working space 28 is pressurized with compressed air via the channel 27. Now the working space 28 is relieved, so that the actuating piston 20 is brought into its upper end position by appropriate relaxation of the springs 25. The cover 8, which is held by the permanent magnet 21, lies against a centering edge 60 on the underside of the cover plate 17. The lid 8 and the can 7 have already been aligned exactly in the middle of the centering surface 30 when entering the vacuum space 59. The vacuum chamber 59 is now evacuated via the connection 29. Thereupon, a protective gas is again introduced into the vacuum space 59 via the connection 29, but only in such an amount that a vacuum in the vacuum space 59 relative to atmospheric pressure is still maintained.

Then the working space 28 is pressurized again, so that the actuating piston 20 with the cover 8 is moved down onto the can 7, namely by pressing a seal 61 located in the edge of the cover against the upper edge of the can 7. Now the vacuum space 59 is complete aerated, whereby the lid 8 is now only pressed on due to the pressure differences between the pressure in the can and the atmospheric pressure. the lifting plate 13 with the can which is now tightly closed due to the atmospheric pressure is moved downward. Subsequently, the two cans 7, which are simultaneously closed in the two degassing devices in the manner described, are brought into the closing station 2 and placed on the two lifting plates 33 of the lifting devices 34. Here the lifting cylinders 31 are now pressurized with compressed air so that the cans are pushed upwards into the sealing bells 36. The respective edge of the cover 8 is pressed against the can 7 by pushing it along on the conically tapering pressing surface 37, whereby the can is finally closed. The stop ring 42 bears against the cover 8 during this displacement movement and centers it by means of the centering collar 43, so that a uniform, centered pressing of the edge of the cover 8 is ensured. This closing movement is ended when the actuating piston 41 moves against the boundary surface 51 of the stop sleeve 49. Now the working space 46 is pressurized with compressed air via the channel 45, whereby the actuating piston is pressed down and the closed can from the Pushes out closure bell 36. This then moves down again on the lifting plate 33. As can also be seen from the drawing, the required travel for the lifting plate 33 in the closing station 2 is only very small; on the other hand, the forces to be applied by the lifting device 34 are relatively high. For this reason, the lifting cylinders 31 are also relatively wide and compact. This means that the working cylinders 11 on the one hand and the lifting cylinders 31 on the other hand can be pressurized with compressed air of the same pressure and, due to the different stroke paths, can each perform their strokes at the same time with a naturally different lifting speed.

If the reducing pieces 52 and 53 are inserted into the degassing chamber 10 and the reducing ring 57 and the reducing closure bell 58 are inserted into the sealing unit 35 in order to close cans of smaller height and smaller diameter, the sequence of the individual work steps is the same as described above.

It must also be added that when the degassing chamber 10 is opened after evacuation and gassing, the can 7 with the lid 8 remains on the lifting plate 13, ie the lid 8 is torn off from the permanent magnet 21, since the magnet 21 is not so strong on the one hand that To keep the weight of the filled can and on the other hand, due to the pressure difference, the lid 8 is already relatively tight on the can. The _R ed _u ornamental piece ₅ 2 and the reducer ₅₇ have a vertical extension which corresponds exactly to the difference between the height of a larger box 7 and a smaller box 7 ', so that the stroke travels of the lifting plate 13 and 33 even at a conversion of the device do not need to be changed.

Claims (5)

1. Apparatus for the vacuum sealing of cans (7, 7'), comprising a cover (8, 8'), the apparatus having a plate (13, 33) which can be moved upwards by means of a lifting device towards a fixed evacuatable bell (14, 36) and which serves to receive a can (7, 7') already provided with a loosely mounted cover (8, 8'), there being provided a device for lifting the cover (8, 8') clear of the can (7, 7'), characterised in that the device for lifting the cover (8, 8') clear of the can (7, 7') comprises an adjusting piston (20) which can be subjected to a pressure medium and which is guided in an adjusting cylinder (18), and that reducers or reducing adapters (52, 53), which are adapted to different can sizes, can be detachably fitted or fixed on this adjusting piston (20), on the one hand, and on the inner wall of the bell (14), on the other hand.

2. Apparatus according to claim 1 having separately arranged venting or degassing station (1) and sealing station (2), characterised in that there ist provided a lifting plate (33) which can be moved from below by means of a lifting device (34) towards a fixed sealing bell (36) and which serves to receive a can (7, 7') having a cover (8, 8'), that the sealing bell comprises an upwardly tapering pressure surface (37) and an adjusting piston (39) which can be subjected to a pressure medium, is guided in an adjusting cylinder (39) and which serves as a pressure pad or back stop and an ejector, and that a reducing sealing bell (58) having a pressure surface (37') can be detachably fitted on the sealing bell and a reducing ring (57) can be detachably fitted on the adjusting piston.

3. Apparatus according to claim 2, characterised in that the path of adjustment of the adjusting piston (41) in the sealing bell (36) can be varied.

4. Apparatus according to claim 2, charac- terlsed in that a stop ring (42) is fitted to the adjusting piston (41) of the sealing bell (36), and that a collar (43, 43') for centering the cover (8, 8') is provided on the stop ring and the reducing ring (57).

5. Apparatus according to claim 1, charac- terlsed in that a centering or locating face (30, 30') is provided on the inner wall of the evacuatable bell (14) and on the associated reducer or reducing adapter (53).

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