GB2078659A - Band straightening device for strapping apparatus - Google Patents

Abstract

A straightening device (30) for a band (10) is positioned to follow a tensioning and closing head (20) as viewed in the direction of band feed. The device (30) and a flap (31) on which it is mounted are pivoted about an axis (27) by a ram (29) away from the band path before the band is tightened around a package (not shown) and cut off from a feed roll, and are pivoted back into the band path for threading of an end of the band into a guide channel (not shown) for the next package. The straightening device (30) preferably comprises three or five rollers. <IMAGE>

Description

SPECIFICATION Strapping apparatus This invention relates to strapping apparatus for strapping bands comprising a guide channel and a device for straightening the band.

This straightening is necessary since the strapping band is curved when it is unwound from the supply drum and also because it is particularly severely bent as it travels through the feed rollers and especially the tensioning rollers and when it is tightened around sharp edges of items which are being strapped. With a bent strapping band there is the danger that the bent piece and especially the leading end will become caught at the edges of the guide channel or may slip out of the open portions of a guide channel formed in this way. It is conventional for such open portions of a guide channel to be in the form of U-shaped rails for several operational reasons.

A strapping device with a straightening device and which is intended to overcome this disadvantage is described in published German Patent Application 1 9 03 105. The construction shown there does control the straightening action in accordance with the curvature and the tension of the strapping band, but using a relatively complicated device. Because of this its method of operation is unsatisfactory, since the accurately straightened strapping band, on tightening the loop, runs through the tensioning rollers again in the reverse direction and is thereby curved, and the part of the strapping band which, after the forming of the closure and the cutting off step, lies between the tensioning rollers and the straightening rollers remains curved, since it does not again run through the straightening device during the strapping of the next package item.

Kinks which can be caused for example by the sharp edges of items being packaged or by the corners of the guide channel will likewise not all run through the straightening device and will create curved ends.

This curved end then constitutes the leading end of the strapping band when it comes to the next strapping operation. The end remains bent since it always lies on the side of the straightening device which has already traversed the device, and this part cannot run through the straightening device again.

In the case of large guide channels and small packages the end of the strapping band can even be rolled several times by the tensioning rollers, and is then very severely curved.

This disadvantage makes itself apparent especially when dealing with strapping bands of low strength and with very thin strapping bands, so that these materials cannot be used for automatic strapping machines because of the frequent breakdowns.

It is an object of the present invention so to shape the leading end of a strapping band that it does not become caught up in the guide channel and that the strapping band is properly guided even in guide channels which may be open on one side, as for example with U-shaped tracks.

In accordance with the invention there is provided strapping apparatus for strapping bands comprising a guide channel and a device for straightening the strapping band, wherein the straightening device is positioned to follow a band tensioning and closing feed, and is pivotable into and out of the plane of the band.

Prior to the tightening of the strapping band the straightening device is pivotally displaced out of the plane of the strapping band, and is only pivotally displaced back again into the plane of the strapping band shortly before the strapping band is unrolled from the supply drum for the next package. The straightening device can comprise three or more rollers into which the leading end of the strapping band is introduced.

One particular advantage lies in the fact that the straightening device can be fitted on to a flap which is located beneath the closing head and which guides and supports the strapping band.

This flap which is known per se is provided in any manner and must be pivoted out of the way before the feeding in of the strapping band. By virtue of the construction of the flap one can do away with any special hinge or any special drive for the flap.

In one embodiment the straightening device comprises two rollers positioned beneath the band and a third roller positioned in the centre above them, with the strapping band being guided through the rollers. The degree of curvature produced by the rollers can be varied by displacing the centrally positioned roller in a direction towards the other rollers. This curvature should be adjusted to be equal and opposite to the curvature of the strapping band. This means that with a very strongly curved strapping band, as for example if it has been bent through 900 around crates, it may be necessary to have more than three rollers in the straightening device. For such severe curvature the straightening device is preferably constructed to include five rollers, with the second and fourth rollers mounted eccentrically and adjustable as to position.

With the apparatus according to the invention it is possible to slide a substantially straight strapping band into the guide channel or, by an appropriate setting of the rollers, to produce a leading end of the strapping band which is directed slightly downwards at the leading end for example. This is particularly advisable with guide channels which have no cover on the side facing towards the article being strapped. This is applicable for example to a stack of bricks which are set on a supporting foundation. The supporting foundation then serves simultaneously as a guide channel. The face of the stack which rests on the support forms the upper cover of the foundation which can be made from arrayed U-shaped iron pieces. Each U-shaped iron piece can be used as a guide channel through which the strapping band Is fed.An unstraightened band will strike against a lump or a gap in the bricks with its face which is concave in relation to the bricks, and thus tend to build up an accumulation of the band with subsequent breakage of the band.

With any straightened strapping band with a convex shape facing away from the bricks the leading end of the strapping band is pressed on to the bottom web of the U-shaped iron guide and consequently slips into the whole guide channel along the bottom webs of the track. Possible catching points in the strapping guide are levelled off so that the strapping band runs through without hindrance and lies looped around the article and is fed back again into the strapping head.

Unstraightened strapping bands can it is true also be fed by complex and costly channel winding mechanisms which are fitted with channel flaps and are inserted into the U-shaped iron pieces, but these usually require a great deal of space, particularly in manufacturing installations where a strapping machine is built in subsequently.

A preferred embodiment of the invention will now be described by way of example and with reference to the accompanying schematic drawings, in which: Fig. 1 is a side view of a strapping system in which the pivotable device of the invention can find application for the straightening of a strapping band; Fig. 2 is a front elevation of the strapping system, being a sectional view taken along the line Il-IlofFig. 1; Fig. 3 is a front view of the strapping head with the straightening device pivoted inwards; Fig. 4 is a front view of the strapping head with the straightening device pivoted outwards; and, Fig. 5 is a side view of the strapping head with the straightening device pivoted inwards and of the feed rollers.

In Figures 1 and 2 the strapping head of a packing system is indicated at 20. A stack 21 of blocks rests on a foundation stand 1 6 and is encircled by guide channels 16, 17, 18, the guide channel 1 6 simultaneously forming a part of the foundation support. The strapping band 10 which is taken from a supply roll 24 is fed by means of a pair of feed rollers 11 and 12 through a closing portion 19 of the strapping head 20, a straightening device 30 comprising three rollers 13, 14, 15, the left-hand guide channel element 17, the foundation support 1 6 which constitutes a band guide, and the right-hand guide channel element 18, to loop around the package and back into the strapping head 20.

In Fig. 5 there is shown a pivotable flap at 31 on which the straightening device 30 is fitted.

Furthermore the flap 31 also carries a band stop edge 9 which stops the strapping band 10 as it runs into the strapping head 20 and which holds the two overlapping band elements over one another until a band gripper which is not shown but which is located in the closing part 1 9 grips and clamps the lower band. The flap 31 with the straightening device 30 can be pivoted by means of a pneumatic cylinder 29 out of the feed plane of the strapping band. Fig. 4 shows the flap 31 with the straightening device 30 pivoted out of this plane.

After the band threading process, and by X reversing the feed rollers 11 and 12, the strapping band 10 can be drawn back in the clockwise sense opposite to that shown, and can be tightened around the stack 21 without the flap 31 and straightening rollers 13 and 14 being involved.

After completion of the tensioning process for the strapping band the overlapping strapping band elements are positively connected together in the closing device 19 and are cut off from the supply roll 24.

The strapping head 20 which is lowered for tightening and closing the strapping band is subsequently raised from the stack 21 by a lifting device which is not shown, so that the flap 31 with the straightening device 30 can then again be pivoted into the feed plane of the strapping band.

The pneumatic cylinder 29 drives the flap 31 by means of a rack 25 and pinion 26 to pivot it about a shaft 27.

The strapping band 10 which is retrieved from the guide channel has now been rolled twice by the pair of feed rollers 11 and 12 and already has a considerable deformation, indeed it is concave in relation to the stack. Upon renewed insertion into the guide channels 16, 17, 18 the strapping band 10 first runs through the straightening device 30.

By appropriate setting of the eccentrically mounted, upper roller 1 5 the strapping band 10 is reshaped so that it is approximately flat or convex relative to the stack. The strapping band 10 runs down the channel guide 22 as it is advanced further. Thus, the leading end of the strapping band with its curvature directed towards the back of the channel guide 22, slides through the Ushaped foundation support 16, is received by the guide channel 1 8 and is fed back into the strapping head 20 until it strikes the band stop edge 9.

The straightening device 30 can include one or more driven rollers. In such a case it is preferred to position the driven straightening device at the point 23 for example. The not yet straightened leading end of the strapping band 1 0 would run through the smooth guide channel 17, especially if this is enclosed on all sides and the ends of the guide channels are socketed into one another to avoid having edges on which the strapping band could become caught.

By means of the described device one achieves an optimum operating reliability. The previously unalterable wave-shaped leading end of the strapping band is straightened into a desirable and advantageous form. Even with complicated channel guides, for example open guides without channel flaps, one is certain of a reliable feeding ef the strapping band.

Moreover, there is no need for costly channel guides or mobile channel interleaves in order to Y guide the strapping band through foundation supports or the like.

Claims (6)

1. Strapping apparatus for strapping bands comprising a guide channel and a device for straightening the strapping band, wherein the straightening device is positioned to follow a band tensioning and closing head as viewed in the direction of band feed, and is pivotable into and out of the plane of the band.

2. Strapping apparatus according to claim 1, in which the straightening device comprises a set of rollers which are pivoted out of the plane of the band for the retraction of the package-looping strapping band from the guide channel and the following tensioning and closing process and which are pivoted through the guide channel.

3. Strapping apparatus according to claim 1 or 2, in which the straightening device is fitted on to a guide flap which is pivotally located beneath the closing head.

4. Strapping apparatus according to any of claims 1 to 3, in which the straightening device comprises three rollers with the middle roller eccentrically mounted and adjustable.

5. Strapping apparatus according to any of claims 1 to 3, in which the straightening device comprises five rollers with the second and fourth rollers eccentrically mounted and adjustable.

6. Strapping apparatus substantially as hereinbefore described with reference to the accompanying drawings.