Source: http://www.google.fr/patents/US5307692
Timestamp: 2013-05-18 22:44:30
Document Index: 656848603

Matched Legal Cases: ['art 2', 'art 3', 'art 2', 'art 3', 'art 2', 'art 3', 'art 2', 'art 3', 'art 3', 'art 2', 'art 3', 'art 3', 'art 3']

Brevet US5307692 - Workstation at a packaging machine - Google�BrevetsRecherche Images Maps Play YouTube Actualit�s Gmail Drive Plus » Recherche avanc�e dans les brevets | Historique Web | Connexion Recherche avanc�e dans les brevets BrevetsA workstation at a packaging machine with a tool having an upper part (2) and a lower part (3) whereby at least one of said parts (3) is driven with a stroke-type movement and a compressive force is exerted via said tool onto a workpiece (4) in the working position, and said tool has a spring arrangement...http://www.google.fr/patents/US5307692?utm_source=gb-gplus-shareBrevet US5307692 - Workstation at a packaging machine Num�ro de publicationUS5307692 AType de publicationOctroi Num�ro de demande07/889,443 Date de publication3 mai 1994 Date de d�p�t27 mai 1992 Date de priorit�29 mai 1991Autre r�f�rence de publicationEP0516147A1EP0516147B1 InventeursHorst E. Kaplan Cessionnaire d'origineKlockner Hansel GmbhKlockner Medipak Gmbh Classification aux �tats-Unis73/862.54153/7753/45373/862.53 Classification internationaleB30B15/28B30B15/00F16P5/00 Classification coop�rativeB30B15/0094F16P5/005B30B15/28 Classification europ�enneB30B 15/00PB30B 15/28F16P 5/00BR�f�rencesCitations de brevets (17) R�f�renc� par (4)Liens externesUSPTO Cession USPTO EspacenetWorkstation at a packaging machineUS 5307692 A R�sum� A workstation at a packaging machine with a tool having an upper part (2) and a lower part (3) whereby at least one of said parts (3) is driven with a stroke-type movement and a compressive force is exerted via said tool onto a workpiece (4) in the working position, and said tool has a spring arrangement (26), the prestress and deflection path of which can be adjusted. A device (25) for measuring the compressive force on the workpiece (4) in the working position is provided and so located in the area of the upper and/or lower part (2 and/or 3) of the tool that it is loaded by the compressive force in the working position.
I claim: 1. A workstation of a packaging machine, in particular a thermoforming station, in which a workpiece is sealed, comprising, a tool having an upper part and lower part disposed along a common axis, drive means for moving at least one of said parts with a stroke type movement toward and away from the other of said parts for driving at least one of said parts into working and open positions along said axis and for exerting a compressive force by said tool onto the workpiece, spring means disposed upon said tool for providing said compressive force, means for adjusting the prestress and deflection path of said spring means, and means for measuring the compressive force on the workpiece and the prestress of said spring means when said lower part is in its open position.
11. In a thermoforming packaging machine workstation having a frame with a tool having first and second parts disposed along a common axis, and drive means for reciprocating said second part toward and away from said first part into working and open positions with respect to said first part, and between which a workpiece is compressively sealed, the improvement comprising: spring means for limiting the sealing force applied by said second piece against said first piece and the workpiece; measuring means for determining the prestress of said spring means in both the working and open position of said tool; and adjusting means for changing the resistance applied by said spring means; whereby said measuring means measures the resistance of said spring mean when said second part is in the working position during each work cycle, and said measuring means and said adjusting means are usable together to measure and set the prestress of said spring means.
12. The packaging thermoforming machine workstation of claim 11, wherein said spring means is disposed upon said tool.
FIELD OF THE INVENTION The invention refers to a workstation at a packaging machine, in particular a thermoforming station, with a tool having an upper part and a lower part whereby at least one of said parts is driven with a stroke-type movement and a compressive force is exerted via said tool onto a workpiece in the working position, whereby the tool has a spring arrangement, the prestress and deflection path of which in the working position can be adjusted. Such workstations are understood to include, in particular, shaping or sealing stations for manufacturing or sealing of packaging containers deep drawn from thermoplastic synthetic foil. The tool has two parts which may, in an appropriate arrangement, be designated as an upper and a lower part and one of which is driven with a stroke-type movement while the other part is either arranged in a stationary position or is likewise driven or, in any case, can be moved to another position. In a sealing station, a lidding foil is sealed onto the moulded foil web under the action of a compressive force. The two foil webs, which are moved with a stepped motion through the entire packaging machine and, thereby, are also worked on at other workstations, represent the workpiece.
BACKGROUND OF THE INVENTION A workstation of the type described above is known. It is constructed as a sealing station at a thermoforming machine. The tool is formed by an upper and lower part, whereby the lower part is driven with a stroke-type movement via a bell crank lever mechanism and acts upon the workpiece, namely the two foil webs, in the working position which represents the closed position of the tool. In doing this it is important that the workpiece is worked upon under compressive force. In order to achieve such a reproducible compressive force, spring arrangements are known which consist of one or more springs. These spring arrangements are provided in the path of one of the two parts of the tool and serve the purpose of creating the compressive force not via the bell crank lever mechanism in direct frame-type support on the workpiece, but rather to allow the force of the spring arrangement to act on the workpiece in the closed position of the tool which might be the working position. For this purpose, the spring arrangement is somewhat compressed in the working position. The spring arrangement is provided in a fettered position. It is known to arrange the prestress and the spring deflection path so that they may both be adjusted. By prestress is meant the force with which the spring arrangement is prestressed in the open position of the tool. By spring deflection path is meant the path through which the spring assembly was compressed into the working position. It is understood that the compressive force, corresponding to the compression or rather, the deflection path of the spring arrangement, exerted by the spring arrangement on the workpiece is greater than the prestress set in the open position of the tool. The setting of the prestress and the spring deflection path is carried out according to the dimensional specifications of the manufacturer of the workstation. As the synthetic foils forming the workpiece have different properties according to the particular case, i.e. in particular, different thicknesses or tolerance ranges for the thicknesses, it is necessary, for correct functioning of the workstation to readjust or rather set the compressive force, for example so that in a sealing station, the lidding foil is so sealed onto the cup foil that long-term tightness is achieved. Accordingly, the setting of the prestress is altered or rather, adapted to a process which is dependent on the skill of the operator. Alterations to the prestress as a consequence of aging, breakage, setting of the spring arrangement, etc. can have a disadvantageous effect on production results and can often remain unnoticed over long production cycles. It can also happen that a lidding foil only becomes detached after several days or even weeks so that appropriate inspections directly after sealing do not detect this error which occurs as a result of a deviation to the compressive force. The number of rejects which can be produced in this way can be considerable.
SUMMARY OF THE INVENTION It is the object of the invention to so equip a workstation of the aforementioned type that the compressive force, which acts on the workpiece in the working position, can be better and more precisely adjusted and can be reproducibly maintained.
BRIEF DESCRIPTION OF THE DRAWINGS The workstation according to the invention will be further explained and described by means of preferred embodiment examples.
DETAILED DESCRIPTION The workstation illustrated in cross-section in FIG. 1 has a frame 1 made up of several parts upon which an upper part 2 and a lower part 3 of a tool 2, 3 are located. The upper part 2 is fixed to the frame 1 while the lower part 3 is mounted such that it may move in the vertical direction with respect to the frame 1. The workpiece 4 to be worked upon is moved with a stepwise motion and stopped between the upper part 2 and the lower part 3, whereby during standstill in the working position the working on the work piece is performed e.g. by sealing a lidding foil onto a cup foil, which together form the workpiece 4. The tool 2, 3 can have the upper part 2 and the lower part 3 directly engaged. However, it is also possible to use tool inserts which are arranged such that they may be exchanged. A drive is provided for moving the lower part 3 back and forth relative to the upper part 2, whereby this drive is frequently derived from the complete drive for the packaging machine. Such a drive shaft 5, passing through the entire packaging machine, is indicated schematically. A cam disc 6 is mounted on this drive shaft 5 and the perimeter of said cam disc has, for example, a curved path which works in conjunction with a swinging arm 7, mounted on frame 1 by means of a joint 8 such that it may swing back and forth. On the other end of the swinging arm 7 there is a pushrod 10 which engages with said arm via a joint 9 which is movable with respect to the frame 1; said pushrod is constructed such that adjustments to the length may be carried out. The pushrod 10 leads to a bell crank lever mechanism having levers 11 and 12 connected to each other via knee joint 13. The dead center position is illustrated in FIG. 1 by the continuous lines while the open position of the bell crank lever mechanism is shown by means of dotted lines. Lever 12 of the bell crank lever mechanism finally engages via joint 14 with the lower part 3 of tool 2, 3. For guiding the lower part 3 on frame 1, guide rods 15 are connected to lower part 3 and said guide rods are guided in slide bearings 16 on frame 1. The pushrod 10 engages via joint 17 with lever 11. Lever 11 is mounted via joint 18 on a thrust pad 19 which is guided in a vertical direction via slide bearing 20 on frame 1. The thrust pad 19 continues via a shoulder 21 into a rod 22 and finishes in a threaded shank 23, upon which at least one adjusting nut 24 is fitted. Here, rod 22 passes through the device 25 for measuring the compressive force on the workpiece 4. Measuring device 25 can consist of a weighing cell, force receiver, piezoelectric element or similar. One side of the device 25 is supported on the shoulder 21 of the thrust pad 19. The other side is supported on a spring arrangement 26 which is here made up of an assembly of Belleville spring washers 27. In principle, one single spring is sufficient for the make-up of spring arrangement 26. The spring arrangement 26 is in turn supported on a bush 28 which can be adjusted via a thread 29 on a yoke 30, whereby the yoke 30 is connected to the frame 1. The adjusting nut 24 is supported by the bush 28 so that, hereby, the device 25 and the spring arrangement 26 are fettered in series. Turning the adjusting nut 24 relative to the threaded shank 23 leads to an alteration or rather an adjustment of the prestress in the spring arrangement 26. Turning bush 28 in thread 29 leads to an adjustment or rather an alteration to the spring deflection path of the spring arrangement 26 in the working position. The adjustment of both variables relative to each other produces the adjustability of the compressive force for the parts of the tool 2, 3 on the workpiece 4 in the working position.
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