Bag opener

Abstract

 Arrangement for completely opening synthetic bags (1) filled with garbage, utilizing a conveyor belt (2) and two rotating wheel-shaped tear and spread elements (3a,3b) disposed above it. Between the tear and spread elements (3a,3b) a brake-element (12) is positioned, to prevent the tear and spread elements (3a,3b) in conjunction with the conveyor belt (2) from passing on the still intact bag (1). Before the bags (1) reach the tear and spread elements (3a,3b) they are, prefera-bly in the upper side, given a transverse cut.

Description

[0001] The present invention relates to an arrangement for opening synthetic bags, such as garbage bags, at least partly filled with, for example, garbage, comprising a transport means, such as a conveyor belt, for a transportation of the bags, a first and a second, at least substantially wheel-shaped, in the operating mode rotating around, respectively, a first and a second axle, tear and spread element, for grabbing the bags on both sides, in which process the bags are torn open and spread out, and their contents at least substantially released.

[0002] An arrangement of this kind is known from application EP-A-0 443 999. The drawback of this prior art arrangement is that, owing to the way the tear and spread elements are disposed, it occupies a large floor area. This is especially a problem if the capacity of an existing garbage processing installation is to be expanded and a number of bag openers are to be arranged in parallel, the more so as the capacity of the bag opener often determines the capacity of the garbage processing installation.

[0003] The arrangement described here is particularly compact, and is characterized in that the first and the second tear and spread elements are positioned above the transport means. This allows a number of bag openers to be placed closely alongside one another, whereby each transport means may dump the opened bag on a conveyor belt running in transverse direction at the end of the transport means. Along this conveyor belt the actual sorting of the garbage takes place, with the synthetic bags usually being removed first. In the manner outlined above, the processing capacity of an available floor area can generally be increased fourfold. Furthermore the arrangement has the advantage that, owing to the chosen disposition of the tear and spread elements, it is virtually impossible for the garbage to get stuck or piled up, so that little maintenance is required.

[0004] An advantageous embodiment of the invention is characterized in that the first axle forms a positive angle, and the second axle a negative angle, with a transport direction of the transport means, causing the upper side of the bag to be torn to both sides and the actual spreading out to be realized.

[0005] A further advantageous embodiment is characterized in that both tear and spread elements are provided with drive means for realizing a peripheral velocity which deviates from a speed of the transport means. It is precisely the speed difference between the two tear and spread elements on the one hand and the transport means on the other that effects the actual tearing result. Preferably the peripheral velocity is chosen to be greater than the speed of the transport means. The tear and spread element can then already begin to move off any released garbage. This effect occurs especially if the tear and spread elements are provided with projections at their circumference and if the transport means is provided with ribs, which are placed at least substantially at right angles to the transport direction.

[0006] The best operation of the arrangement is obtained if the bags are placed centrally on the transport means; only then will the tear and spread elements act symmetrically on the bags, and a complete opening and emptying be achieved. To this end the arrangement may be equipped with guide rails, centring the bags while they are transported to the tear and spread elements. A centring effect can also be achieved by giving the earlier mentioned ribs a form somewhat resembling a V.

[0007] A requirement the user of an arrangement of this kind wants to be met is that glassware, such as bottles, contained in the bags should hardly ever break. Yet another advantageous embodiment of the invention is therefore characterized in that the tear and spread elements are at least in a vertical sense movably fitted. The tear and spread elements may for example be fitted using springs, or hinged using a counterweight. Besides, in order to further reduce the risk of breakage, the circumference of the tear and spread elements may be provided with a layer of springy material, such as rubber, in which the projections are then fitted. With this the tearing effect of the projections is retained, while a projection thus embedded in rubber can now, at least to some extent, give way, which may generally prevent a bottle from breaking.

[0008] It has been experimentally determined that a still better operation of the arrangement is achieved by holding back the bag during tearing and spreading, with on the lower side the ribs and on the upper side the tear and spread element acting on the bag. A very advantageous embodiment of the invention is therefore characterized in that a brake-element is positioned between the tear and spread elements, which impedes the transportation of a bag to be opened by the transport means and the cooperating tear and spread elements grabbing the bag to be opened. If, moreover, the tear and spread elements and the brake-element are mounted at the very back above the transport means, a virtually complete separation of the garbage and the bag is achieved, with the bag leaving the transport means last and therefore being easy to remove. It may further be noted that the brake-element originally comprised of a knife, located between the tear and spread elements which, while the bag went past, cut its upper side open lengthwise. Surprisingly, the arrangement proved to be functioning better as the knife became blunted, which gave rise to the described improvement, where the knife has no longer any cutting function at all.

[0009] A still better result, i.e. a still better separation of the garbage on the one hand and the bag on the other, can be obtained by equipping the arrangement with vibratory means, mounted between the first and the second tear and spread element, to produce a horizontal, at least substantially symmetrical vibration around the transport direction of the combined tear and spread elements. This causes any garbage remaining in corners of the bags to be successfully removed.

[0010] A further advantageous embodiment of the arrangement is characterized in that there is provided at least one cutting element, located, in the transport direction, before the tear and spread element. The best result is achieved if the cutting element is arranged to make a cut in the upper side of the bag to be opened. A particularly advantageous result is achieved if the cutting element is arranged to cut the bag to be opened in a direction which is at least substantially at right angles to the transport direction. As is known from the prior art, the cut can be made using, for example, a knife, a sawing arrangement, an electrically heated wire, or a laser. By suitably controlling such a cutting element it is possible to obtain a transverse cut running practically across the centre of the bag. With a bag preprocessed in this manner, on the transversely positioned conveyor belt the bag will practically always end up on top of its contents, simplifying the automatic or manual removal of the bag.

[0011] The invention will now be further explained with reference to the following figures, in which:

Fig. 1

is a schematic representation in side view of an arrangement according to the invention;

Fig. 2

is a schematic representation in top view of an arrangement according to the invention.

[0012] Fig. 1 shows a possible embodiment of the arrangement according to the invention, with bags 1 filled with garbage being transported, with the aid of a conveyor belt 2 provided with a drive (not shown), to two wheel-shaped tear and spread elements 3a,3b positioned above the conveyor belt. Tear and spread element 3b being located exactly behind tear and spread element 3a, it is therefore not visible in Fig. 1. The tear and spread elements 3a,3b are provided with drive means 4a,4b, for example electric motors, which drive the tear and spread elements 3a,3b such that they operate in conjunction with conveyor belt 2, while their peripheral velocity is greater, for example 50%, than the transporting speed of conveyor belt 2. Conveyor belt 2 is further provided with ribs 5, placed at right angles to the transport direction. It is precisely the speed difference between the conveyor belt 2 on the one hand and the circumference of the two tear and spread elements 3a,3b on the other which accomplishes that the bag is torn open. By positioning tear and spread elements 3a,3b such that they form an angle with the transport direction, in the sense that they diverge viewed in the transport direction, the desired spread can be accomplished. The bags thus cut open and spread next land on, for example, a conveyor belt 6, which for illustration purposes is positioned here at right angles to conveyor belt 2. Conveyor belt 6 may alternatively be positioned below conveyor belt 2, such that released garbage and empty bags are moved off in the direction from where the filled bags are fed in. It has been found that bags making a 180° turn together with the conveyor belt tend to be held back somewhat, presumably on account of electrostatic charging, which causes them to drop later than the garbage so that they land behind it. This makes the collecting of the bags simpler still.

[0013] In order to prevent any bottles that may be present in the garbage from breaking, tear and spread elements 3a,3b are mounted on a frame 7, which can rotate around an axle 8, the acting forces being further reducible using a counter-weight 9 or a spring (not shown). The actual tearing action of tear and spread elements 3a,3b is achieved by accommodating projections 10 in their circumference. Projections 10 increase the risk of bottles present in the garbage being broken. To reduce this risk the circumference of tear and spread elements 3a,3b is provided with a rubber layer 11, in which the projections 10 are fitted. This allows a projection 10 to give way to a certain extent if a hard object, such as a bottle, is encountered. Projections 10 are preferably fitted exchangeably in rubber layer 11, for example using a threaded connection, as some of them may break during operation.

[0014] Between the tear and spread elements 3a,3b there is positioned a brake-element 12, which in this case has the form of a knife and is fitted to a frame 13, which frame 13 can likewise rotate around axle 8. Although brake-element 12 gives the impression of having a cutting function, this is, at least practically, not the case. Brake-element 12 is exclusively there to prevent the intact bag 1 from shooting undisturbed past tear and spread elements 3a,3b. For this reason the edge of brake-element 12 is not sharp but rather rounded off. To further increase the braking effect the edge may be provided longitudinally with a number of ridges, constructed without sharp protrusions and carefully deburred to prevent remnants of synthetic bags catching on them. Brake element 12 may also for example be constructed as one or more chains, which are suspended from frame 13 and impede the progress of bag 1.

[0015] With the arrangement described above approximately 90% of all offered bags can be opened such that the empty bags can be disposed of without trouble, which in the field is usually found acceptable.

[0016] A further enhancement can be achieved by fitting, before the tear and spread element, a cutting element 14, making a central cut in the upper side of the bags at right angles to the transport direction. With such a cut made, practically all bags are completely opened in the subsequent process, with the contents initially lying on top of the opened bag, the reversal of which, contents below and bag on top, is achieved on conveyor belt 6, provided there is an appropriate difference in height between transport arrangement 2 and conveyor belt 6, so that the empty bag can easily be removed. Cutting element 14 in the arrangement shown is constructed as an electrically heated wire, which is lowered with the aid of actuators 15a,15b (the latter not shown) the moment when bag 1 has arrived exactly below it, actuators 15a,15b being controlled with the aid of a sensor (not shown) detecting the presence of a bag. Cutting element 14 may, of course, also be constructed as a knife, a saw or a laser. In the latter case actuators 15a,15b can be eliminated, and the laser beam should, at the right moment, according to a method known in the art, make a scan at right angles to the transport direction.

[0017] Fig. 2 shows the same embodiment of the invention in top view, highlighting the relative positions and orientations of tear and spread elements 3a,3b and of brake-element 12, with frame 13 also being visible. The positioning of a vibratory element 16 can be seen, too, which here takes the form of a pneumatically controlled cylinder. The operation is as follows. While bag 1 is being torn open, tear and spread elements 3a,3b will be lifted by the bag, with frame 7 rotating around axle 8. Frame 7 rotates back as soon as the bag is at least practically empty. This reverse rotation may be monitored through a detector (not shown), with the cylinder then being controlled such that, symmetrically around the transport direction, tear and spread elements 3a,3b will execute a few vibrations. For this the elasticity of frame 7 may be utilized, but alternatively frame 7 could be fitted with two hinges 17a,17b to facilitate vibrating. A suitable vibration frequency is 0.5 - 2 Hz.

[0018] The desired vibration may also be generated without a vibratory device and hinges, by constructing the arms of frame 7 such that they can easily be set vibrating, and by selecting the length and the rigidity such that the natural frequency of frame 7 lies within the above-mentioned frequency band. During the tearing open of the bag the tear and spread elements 3a,3b will again be lifted. At the same time both elements experience a movement towards each other, the movement being occasioned by forces arising on account of the angles the two elements form with the transport direction. When the bag has become at least practically empty, tear and spread elements 3a,3b will return to the initial position, where they can rotate freely just above transport means 2. Since this occurs fairly abruptly, frame 7 starts vibrating spontaneously, which causes a practically empty bag which is still attached to tear and spread elements 3a,3b to be given an extra shaking, which loosens any garbage that may be left in the corners of the bag.

Claims

1. An arrangement for opening synthetic bags, such as garbage bags, at least partly filled with, for example, garbage, comprising a transport means, such as a conveyor belt, for a transportation of the bags, a first and a second, at least substantially wheel-shaped, in the operating mode rotating around, respectively, a first and a second axle, tear and spread element, for grabbing the bags on both sides, in which process the bags are torn open and spread out, and their contents at least substantially released, characterized in that the first and the second tear and spread elements are positioned above the transport means.

2. Arrangement as claimed in claim 1, characterized in that the first axle forms a positive angle, and the second axle a negative angle, with a transport direction of the transport means, for the realization of the spreading out.

3. Arrangement according to claim 2, characterized in that both tear and spread elements are provided with drive means for realizing a peripheral velocity which deviates from a speed of the transport means.

4. Arrangement as claimed in claim 3, characterized in that the peripheral velocity is greater than the speed of the transport means.

5. Arrangement as claimed in claim 3 or 4, characterized in that the transport means is provided with ribs, which are placed at least substantially at right angles to the transport direction.

Drawing