EP0452338B1 - U-shaped staple and device for closing bags and tubes - Google Patents

Abstract

U-shaped staples for closing bags and tubes in continuous strips comprise a base (7) and two branches (4) whose ends are bent outwards to form a connecting bridge (2) which can be detached from the individual staples in a strip (1) of staples. Damage to the closed package and other packages can be caused by burrs which are formed when the individual staples are detached from the strip (1) and which project beyond the width of the staple. To resolve this problem, the strip of staples has an approximately parallel-sided section (3) in the region of the ends (6) of the branches, which is narrower than the strip. The regions of the ends (6) of the branches, which are bent outward, therefore rest uniformly against the outer sides of the branches (4), within the width of the strip, without burrs which project beyond the width of the strip. A device for closing bags and tubes by means of these staples has a closing punch (9) which co-operates with a die (8). The effective surface (29) of the punch has a groove (10) whose width is equal to that of the staple and whose depth is less than the total thickness of the branch involved in the closing process. During the closing process, the side walls of the groove (10) guide the ends (6) of the branches and ensure that the ends (6) of the branches of the staples are pressed against the outside of the branches (4) of the staples without forming burrs.

Description

The invention relates to a U-shaped closure clip made of tape material for bags and hoses and a closure device with a closure stamp and a die. The closure clip consists of a clip base and two legs, the ends of which are bent outwards and form a separable connecting web with the leg ends of adjacent clips. To close a packaging envelope, the section of the bag or tube (eg a filled sausage casing) gathered into a braid is inserted into the clip, which in turn is held in a die which is shaped in accordance with the clip base. The limbs of the clip are then cut off from the clip strand with the aid of a closing stamp that is moved against the die, bent around the packaging braid, and the braid is thus closed by the clip. The ends of the legs are pressed against the outside of the legs.

When the individual clips are separated from the ribbon-like strand, cutting burrs occur at the point of separation in the area of the connecting web. After the leg ends have been closed and pressed against the outside of the leg, they can protrude laterally beyond the bandwidth of the clip if the bandwidth of the entire clip including the connecting web is approximately constant, as was the case with previously used clip clips (DE-C-10 78 495, DE-A-26 06 658 and DE-A-31 48 757). As a result, there is a risk that the sealed packaging, such as the casing of a sausage, will be damaged. There is also the risk that during further processing, e.g. when cooking, other packaging will be injured. Finally, in cases where the sealed sausage is welded into an evacuated secondary packaging, this can be damaged by the separating burr, which has often caused the user to cut the sealing clip of the sealed sausage before packaging in the secondary packaging. This additional effort is time consuming and costly.

Therefore, in the closure clip strand known from DE-A-17 61 616, the connecting web has an arcuate constriction on both sides, approximately symmetrical to the ideal dividing line, which reduces the bandwidth on both sides. This should prevent the burrs of the cutting edges from projecting laterally on the leg ends bent outwards after the closure. This has also been largely achieved so that in many cases it was no longer necessary, e.g. cut off the closing clip from the sausage before a second packaging.

However, it has been shown that the bent leg ends, as part of the connecting web, are not always centered on the outer side of the legs due to the closing stamp be pressed. Rather, there is sometimes a slight tilt when closing, so that the leg ends are pivoted slightly to the side. You then protrude laterally over the adjacent leg. The required avoidance of the ridges projecting beyond the bandwidth was therefore not achieved with sufficient certainty.

The invention is based on the object of specifying a clamp closure for bags and hoses which ensures reliable closure and has no burrs projecting beyond the bandwidth, and a device suitable for its manufacture.

According to a first aspect of the invention, this object is achieved in that, in the case of a closure clip as part of a band-shaped closure clip strand, the reduction in the bandwidth of the leg ends also extends over a section of the legs adjoining the ends and, in the region of the reduced bandwidth, the outer edges of the ends and sections of the legs run approximately parallel. Due to their parallel edges, the narrower legs can be guided in the separating and closing punch during the closing process - for example with the help of the lateral edges of a groove or such a depression. The closing movement of the legs is not hindered by this, but its lateral pivoting out (center offset) is reliably avoided. At the same time, the separating and closing stamp also acts directly on the legs next to the bent leg ends and closes the clamp.

In addition - in contrast to the closure clip known from DE-A-17 61 616 - the bandwidth is also reduced at the bend points of the leg ends and therefore a lower bending resistance is opposed to the pressing of the leg ends when closing. That has a special effect with thick strip material and is particularly important with regard to the shortness of the leg ends to be bent and the correspondingly small lever arms and for the reliable guidance of the leg ends in the stamp. As a result, the bent leg ends are also pressed closer to the legs, which further reduces the risk that the locking clip will later cause damage. The higher surface pressure when closing, which pushes the outer cutting burr almost completely away, acts in the same direction.

From GB-A-920 335 it is known to positively guide a locking clip during the closing in the separating and closing tools, with the aid of a rib which is almost completely circumferential around the band of the - individual - clip and which is supported by corresponding grooves in the Closing stamp and the die is added. It is disadvantageous that the rib stiffens the clip and thereby increases the required closing pressure; furthermore the fact that no pressure is exerted on the clamp in the area of the unsupported rib projecting into the groove, so that uneven bending and flow processes in the clamp result when the clamp is closed. It was not possible to derive any suggestion that in the manner according to the invention only the ends of a clip separated by severing from a strand and thereby achieve the advantageous effects set out above could be obtained. DE-A-37 15 626 was also unable to provide such a suggestion, because - in order to achieve another goal - it suggests a change in the strip thickness and not in the bandwidth.

The reduction in the bandwidth is between 5 and 40%, preferably between 10 and 30%.

A preferred embodiment of the invention is that a groove or U-shaped embossing is attached to the underside of the band material at the transition from the clip leg to the connecting web, as is known per se from DE-A-17 61 616. With this U-shaped embossing, the advantages which are described in the aforementioned prior publication are additionally achieved in the closure clip according to the invention.

Another preferred embodiment of the invention is that in a closure clip according to the invention, which has the aforementioned U-shaped impressions, a hollow curvature is provided in the longitudinal direction on the bottom or top of the connecting web between the U-shaped impressions, in the middle of which the strip thickness is still is less than in the area of the U-shaped impressions. The closure clip according to DE-A-17 61 616 already has a hollow curvature on the upper side of the connecting web. However, this hollow curvature is longer than the distance between the mutually facing limits of the U-shaped impressions. Therefore, a smaller strip thickness is created between the U-shaped embossing and the outlet of the curvature than in the area of the center of the curvature, i.e. at the later separation point. As a result, there is a risk that when winding up and unwinding the staple strand into a roll, an arbitrary kinking occurs between the individual fastening clips at that point of the smallest strip thickness, that is to say during the U-shaped embossing. However, it is desirable that the clamp strand bends in the middle of the connecting web when winding up, so that a clamp strand without a kink is present in the U-shaped embossments during unwinding. With such kinks in the U-shaped embossments, there is a risk that the clamp inserted into the die during feed will be tilted and that no perfect closure can be brought about.

The proposed preferred attachment of the hollow curvature on the bottom or top between the U-shaped embossments ensures that a predetermined bending point is created in the middle of the connecting web and prevents kinks at the U when winding and unwinding the staple strand -shaped impressions arise.

The fact that the strip thickness in the middle of the hollow curvature is less than in the region of the U-shaped embossment additionally means that, also as a result of the reduced strip width according to the invention, the smallest cross section of the strip material is present at the separation point. As a result, the abrasion that often arises in the form of leaves is largely avoided during the separation process, while such abrasion occurs occasionally in a thicker overall cross section, especially in the case of food packaging.

Another aspect of the invention is that (only) the closing stamp of the closing device has a groove, the groove corresponds to the reduced width of the ends of the closure clip leg. Then the closing punch according to the invention can also act directly on the other legs next to the leg ends, which are usually bent outwards, and exert closing pressure. The depth of the groove must be less than the thickness of the leg ends bent outwards so that they are fully pressed.

The arrangement is preferably also such that the groove has a depth that decreases in its longitudinal direction (circumferential direction of the clip) from the center to the ends. This also ensures that the closing force is distributed as evenly as possible to the clamp during the closing process without impairing the guiding function of the groove in the region of the leg ends.

Finally, it is advantageous to round off the corners of the groove cross section, because in this way sharp edges on the most outstanding sections of the closed clip are avoided. The clamp can also be removed more easily after the closing process of the closing device.

• Fig. 1 einen Verschlußklammerstrang in perspektivischer Darstellung:
• Fig. 2a einen abgewandelten Verschlußklammerstrang in Seitenansicht;
• Fig. 2b einen Querschnitt des Verschlußklammerstrangs in Fig. 2a;
• Fig. 3 (a und b) weitere Abwandlungen des Verschlußklammerstrangs in einer der Fig. 2a entsprechenden Seitenansicht;
• Fig. 4 eine erfindungsgemäße Verschließvorrichtung in Seitenansicht;
• Fig. 5 einen zugehörigen Verschließstempel im Mitten-Querschnitt;
• Fig. 6 die Verschließvorrichtung der Fig. 4 in perspektivischer und in der Schnittebene der Fig. 5 geschnittener Darstellung; und
• Fig. 7 eine der Fig. 6 entsprechende Darstellung einer Verschließvorrichtung zum Verschließen der Verschlußklammern gemäß dem ersten Aspekt der Erfindung.

The invention is explained below with reference to the drawings. It shows:

• 1 shows a closure clip strand in a perspective view:
• 2a shows a modified closure clip strand in a side view;
• 2b shows a cross section of the closure clip strand in FIG. 2a;
• 3 (a and b) further modifications of the closure clip strand in a side view corresponding to FIG. 2a;
• 4 shows a closing device according to the invention in a side view;
• 5 shows an associated closing punch in the central cross section;
• FIG. 6 shows the closing device of FIG. 4 in a perspective view and a section in the sectional plane of FIG. 5; and
• FIG. 7 shows an illustration corresponding to FIG. 6 of a closing device for closing the closing clips according to the first aspect of the invention.

In the closure clip strand 1 in FIG. 1, the ends 6 (see FIG. 2) of the legs 4 forming the connecting webs 2 and in each case a small section 3 of the legs 4 are reduced in bandwidth parallel to the longitudinal axis of the closure clip strand. The side surfaces 6a of the leg ends 6 and the side surfaces 3a of the sections 3 of the legs 4 run parallel to one another. The (later) separation point in the connecting web 2 is indicated by the dash-dotted line 2a. The bracket base is designated 7.

2a, 3a and 3b show the closure clip strand 1 from FIG. 1 with U-shaped impressions 11 at the transition of the clip legs 4 to the connecting web 2. In FIG. 2b, the closure clip strand 1 from FIGS. 2a, 3a and 3b with the Side surfaces 3a of section 3 with reduced bandwidth are shown in section.

As can be seen in FIG. 2a, the material cross section 12 in the middle of the connecting web 2 is larger than the material cross section 13 in the area of the U-shaped embossments 11 .

3a therefore shows the closure clip strand 1 of FIG. 2a with a hollow bulge 14 on the underside of the connecting web 2 between the U-shaped impressions 11 and FIG. 3b with a hollow bulge 16 on the top of the connecting web 2 between the U-shaped ones Embossments 11. When rolling up and down, the closure clip strand only bends in the middle of the connecting web 2, the later separation point 2a.

The closing device according to the invention is now described. The matrix 8, of which only the upper part, which is of interest here, is shown in FIG. 4, has a trough-shaped recess 22 which, at the beginning of a closing process, partially accommodates a closing clip 30, which is already closed in FIG. 4, and the necessary during the closing process Abutment forms. A corrugation 24 on the bottom of the recess 22 holds the closure clip 30 in the desired position during the closing process, when this begins with the cutting of the clip 30 from a strip of contiguous clips (FIG. 1); for this purpose, the cutting edges 25 and 26 work together (on the closing punch).

The closing ram 9 is movable in the direction of arrow 28 (which can be a swiveling movement with a large swiveling radius). 4, 6 and 7, the closing punch 9 has reached its lower end position - at the end of a closing process.

The active surface 29 of the closing die 9 is, as can be seen in FIG. 4, concave. In the Wilkfläche 29 a groove 10 is incorporated, the depth of which is greatest in the middle (at 31) and decreases towards the ends; in the example to zero. The greatest depth of the groove is less than the thickness of the legs 4 of the bracket 30; it only reaches the (smaller) thickness of the leg ends 6 at their outlet.

Fig. 5, which only shows the closing stamp 9, shows the cross section of the groove 10, which is rounded in the corners 32. In practice, when it comes to sealing sausages, in which the end of one sausage and the beginning of the next sausage are sealed at the same time, two sealing devices of the type shown are arranged one behind the other, i.e. in the plane of the drawing, so that to the left of the 5 shown in Fig. 5 another sealing mirror formed mirror image (with the associated die). There is a certain space between the two stamps through which a cutting knife can be moved. The drawings show the closing devices on an enlarged scale: the width of the closing punch 9 shown in FIG. 5 is for example 13 mm, the width of the groove 10 5 mm.

After a closure clip 30 has been separated from the clip strand - and before it is closed - the closure clip 30 has an upwardly open U-shape with diverging legs 4, to which leg ends 6 angled into the horizontal line are connected. These are grasped by the groove 10 during the closing process and guided laterally in this. With a further stroke of the closing die 9, the legs 4 bend around the packaging braid 5, the leg ends 6 firmly resting on the outside of the legs 4, which ultimately results in the shape shown in FIGS. 4 and 6. 6, the cut braid 5 of a sausage casing or the like is indicated within the closed bracket 30.

The closure clip 30 in FIG. 7 is the one described above, in which the width of the leg ends 6 and a subsequent part 3 of the legs 4 are reduced. The width of the groove 10 is correspondingly reduced both sides of the groove 10 located sections of the active surface 29 of the sealing die 9 act at least at the end of the sealing process directly on the shoulders 4a of the locking clip 30, which are formed after the leg sections 3 of reduced width from the subsequent full-width sections. The drawing shows that the leg ends 6 (of smaller width) as parts of the former connecting web 2 have been pressed centrally against the outer surface of the legs 4.

Claims (9)

1. A U-shaped sealing clamp of strip material for bags and tubes, comprising a clamp base (7) and two flanks (4), the ends of which are bent outwards, forming a separable connecting bar (2) with clamps adjacent to the flank ends in a non-separable clamp part (1), and having a reduced strip width on both sides, characterised in that the reduction of the strip width also extends respectively over one section (3) of flanks (4), connecting with ends (6), and in the region of the reducing strip width, the side surfaces (6a, 3a) of ends (6) and sections (3) of flanks (4), extend approximately in parallel.
2. A sealing clamp according to Claim 1,
   characterised in that the strip width is reduced by between 5 and 50%, preferably by between 10 and 30%.
3. A sealing clamp according to Claims 1 and 2,
   characterised in that on the underside of the strip material at the junction of the clamping flanks (4) to connecting bar (2) there is a U-shaped impression (11) arranged respectively.
4. A sealing clamp according to Claim 3,
   characterised in that the connecting bar (2) between the U-shaped impressions (11) has a concave curvature (14, 16) in the longitudinal direction, in the centre of which the strip thickness (cross-section 15) is less than in the area of the U-shaped impression (11).
5. A sealing clamp according to Claim 4,
   characterised in that the concave curvature (14) is arranged on the underside of the connecting bar (2).
6. A sealing clamp according to Claim 4,
   characterised in that the concave curvature (16) is arranged on the upper side of the connecting bar (2).
7. A device for sealing bags and tubes by means of a U-shaped sealing clamp of strip material according to one of the preceding claims, having a sealing ram (9) and a matrix (8), and against which the sealing ram can be so-positioned that it presses the flanks (4) of a clamp supported on the matrix against one another and presses into the base (7) of the clamp, and whereby the sealing ram has a groove (10) in its working surface which extends in the circumferential direction of the clamp and which form-sealingly interacts with the sealing clamp during sealing, characterised in that the width of the groove (10) corresponds to the reducing width of the ends of the sealing flanks and the depth of which is less than the thickness of the outwardly bent flank ends (6).
8. A device according to Claim 7, characterised in that the depth of groove (10) diminishes in the longitudinal direction from the centre (31) towards the ends.
9. A device according to Claim 7 or Claim 8, characterised in that the corners (32) of the groove cross-section are rounded.

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