DEVICE FOR CUTTING OFF WRAPPING STRINGS ON WRAPPED ARTICLES

Abstract: A device for cutting off wrapping strings or bands (4) on wrapped articles, such as bales of pulp (1), comprises a cutting-edge holder (15) which, from a first inoperative position located outside the boundary surfaces of the wrapped article (1), can be projected along a path of movement towards the article to a second position in which the cutting edge is located at least in the same plane as one of the boundary surfaces of the article. The device further comprises a sensor (19) for sensing, while the article is moving in the longitudinal direction in relation to the device, the position of a separate wrapping string (4) and causing the cutting-edge holder (15) to project towards the article in order to cut off the wrapping string when this crosses the path of movement of the cutting-edge holder.

Description: DEVICE FOR CUTTING OFF WRAPPING STRINGS ON WRAPPED ARTICLES Background of the Invention The present invention relates to a device for cutting off wrapping strings or bands on wrapped articles, such as bales of pulp, comprising a cutting-edge holder which, from a first inoperative position located outside a bound¬ ary surface of a separate article, can be projected at high speed towards said article to a second position in which the cutting edge is located at least in the same plane as the boundary surface of the article while cutting off a separate wrapping string on the article. Devices for cutting off wrapping strings on wrapped articles are known in the art. SE 465,459, for instance, teaches a cutting device comprising a foot member and a toothed wheel which are arranged on a movable arm and adapted to be applied against a boundary surface of the article passing by on a conveyor. The toothed wheel serves to seize a separate wrapping string and lift it onto the upper side of the foot member to remove the string some¬ what from the article and enable it to be cut off. Cutting can be performed e.g. between a shearing means and an abutment. One drawback of this cutting device is that the foot member and the toothed wheel have to be applied, and trail and rotate, respectively, against the outside of the pass¬ ing article. As a rule, this does not involve any incon- veniencies when the outside of the article is smooth. How- ever, some articles, e.g. bales of pulp, are usually wrapped in paper which is often torn or folded. As a result, the paper often catches on the foot member, caus¬ ing a stoppage. Further, the bale itself may be damaged, with parts of the paper sheets projecting beyond the normal boundary surface of the bale, thereby making it impossible for the toothed wheel and the foot member to intercept the string. Should the cutting operation fail for some reason or other, e.g. because the wrapping paper has got stuck, the bale may catch in the foot member, thereby damaging the equipment. Furthermore, SE 394,096 discloses a device for sever- ing the wrapping strings on bales of pulp with the aid of impact means. Each such means is supported on the end of a pivot arm which can be pivoted towards and away from a lateral surface of the bale. To ensure that all the wrapping strings on the bale are cut off, a plurality of impact means do, however, have to be arranged and be simultaneously swung at high speed towards the stationary bale, the impacts being evenly distributed over the whole lateral surface. Naturally, such a device consumes excessive amounts of energy, since but a few impact means actually cut off a wrapping string. Further, there is a considerable risk that the wrapping strings are flipped away in an uncontrolled fashion when being cut off, which makes it difficult, or even impossible, to remove the strings by an automatic device. Summary of the Invention The present invention aims at obviating the above drawbacks inherent in prior-art cutting devices and providing a device which has a low energy comsumption and which averts the risks of functional trouble due to damage to the wrapping paper or to the article itself. Another aim of the invention is that a failure to cut off a wrapping string should not cause the article to be caught in the cutting device. Yet another aim of the invention is to enable the string to be cut off also when the surface of the article has been damaged. A further aim of the invention is that the wrapping strings should be maintained in their positions on the bale also after cutting. These and other aims of the invention are achieved by a device for cutting off wrapping strings, which is more specifically characterised in that the cutting-edge holder is located beneath the article, more precisely between two endless conveyor elements or chains, so that the wrapping string, when cut off, will be retained in position by be¬ ing squeezed between the article and each of the conveyor chains, and that the device has a sensor for sensing, while the article is moving in the longitudinal direction in relation to the device, the position of a separate wrapping string and causing the cutting-edge holder to project towards the article in order to cut off the wrapping string when this crosses the path of movement of the cutting-edge holder. Brief Description of the Drawings In the drawings. Fig. 1 is a side view of a device for removing wrapping strings from bales of pulp; Fig. 2 is a top view of the device in Fig. 1; Fig. 3 is an end view from the left of the device in Fig. 1; Fig. 4 is a side view of a cutting device according to the invention; Fig. 5 is a top view of the cutting device in Fig. 4; and Fig. 6 is an end view of the cutting device, as seen in the direction of conveyance. Description of a Preferred Embodiment A station which is arranged at a conveying path for bales of pulp and in which wrapping strings are automati¬ cally removed from the bales will first be described with reference to Figs 1-3. A separate bale 1 is transported on a conveyor 2 in the direction indicated by the arrow 3. The bales do not always have the same number of wrapping strings 4, but usually have two strings extending in two orthogonal directions. An inventive cutting device, generally designated 5, is located between two endless driving elements or chains 6 of the conveyor 2, more precisely substantially beneath a plane of conveyance defined by the conveyor 2. An intercepting means 7 is supported on a level above the bales by an upright frame 8, a pivotable bracket arm 9 projecting from the upper end thereof, and parallel-displacement rods 10 directed down¬ wards from the bracket arm. By means of a pneumatic cylin¬ der 11, the intercepting means 7 can be raised to an upper inoperative position, as illustrated by dashed lines in Fig. 1. The cutting device 5 is arranged just before the intercepting means 7, so that the strings cut off are immediately intercepted and retained by the intercepting means 7. In this description, the terms "before" and "in front of" are used to indicate a position in a direction against the normal direction of conveyance of the bales of pulp. Correspondingly, the terms "after" and "behind" are used to indicate a position in the direction of conveyance of the bales of pulp. When the bales have strings extending in two ortho¬ gonal directions, the separate bale 1 should first be conveyed through the station oriented in one direction, the strings 4 extending transversally of the direction of travel of the conveyor being cut off by the cutting device 5 and immediately intercepted and retained by the inter¬ cepting means 7. At a turning device, generally designated 12, the bale stops, is lifted and rotated through a quarter of a turn by the cylinder 13, and is lowered onto the conveyo .. The bale is then backed to the area in front of the cutting device 5 and again conveyed through the station, the other pair of wrapping strings being cut off, and removed by the intercepting means 7. All the strings have now been removed, and the bale can thus be conveyed to the next processing station. At this point, the intercepting means 7 is holding four wrapping strings and is raised to its upper position. By the pneumatic cylinder 14, the bracket arm 9 and the intercepting means 7 are swung aside, as illustrated by dashed lines in Fig. 2, and the strings are then con¬ veniently dropped into a container, for instance a wire coiling reel. To minimise idle time, the intercepting means may instead be swung out and drop the strings after only two strings have been removed from the bale and while the bale is being conveyed to the turning device 12, turned and then backed to the area in front of the cutting device. When the bale returns to the area in front of the cutting device 5, the intercepting means 7 is then again in posi¬ tion to intercept and remove the two remaining strings on the bale. Another bale may then immediately be passed through the station and its first two strings be removed. Figs 4.-6 illustrate the construction of the inventive cutting device 5 in more detail. The cutting device includes a cutting blade 15 which, by a pneumatic cylinder 16, can be displaced between a lower inoperative position, indicated by full lines in Fig. 4, and an upper cutting position, indicated by dashed lines in Fig. 4. A line 17 indicates the level of the upper plane of the conveyor 2, i.e. the plane in which the bales are moved along the conveyor. As appears from Fig. 4, the cutting edge 18 of the blade 15 is, in the first inoperative position, locat¬ ed at a distance beneath the plane of conveyance of the bales and, in the second projecting position, located at a distance above this plane. Further, the path of movement of the cutting blade is linear and substantially perpen- dicular to the plane of conveyance 17. - A sensor 19 is arranged immediately in front of the path of movement of the cutting blade. In the preferred embodiment, the sensor 19 is an inductive sensor that responds to metallic objects in its immediate vicinity, i.e. it can sense the passage of a metallic wrapping string. When doing so, the sensor transmits a signal to an electric control circuit (not shown) which, with a certain delay, causes the pneumatic cylinder 16 to project the cutting blade 15 in order to cut off the wrapping string when this crosses the path of movement of the cutting blade. As appears from the drawings, the sensor 19 and the path of movement of the cutting blade are located in the space between two rotatable wheels or circular discs 20 having concentric axes of rotation. The wheels 20 are arranged at one end of a U-shaped pivot arm 21 -which is pivotable about a shaft 22 acted upon by a torsional spring. This spring urges the wheels 20 towards an upper end position, as indicated by dashed lines in Fig. 4. When a bale is moved over the device, the wheels 20 will be depressed to a downwardly-pivoted position, as indicated by full lines in Fig. 4. The pivotal movement of the wheels 20 and the pivot arm 21 acts on a limit switch 23, which in turn acts on the control circuit of the cutting blade so as to prevent the blade from being projected when the wheels 20 are unloaded, in spite of the fact that the sensor 19 detects the presence of a metallic object. It is not until the wheels 20 are loaded and depressed that the cutting blade 15 can be caused to project. The cutting blade is thus prevented from projecting unintentionally, e.g. when the device is being repaired or serviced. Con¬ veniently, the required loading pressure on the wheels 20 is set so high that a human being is unable to release the cutting blade and thus risk being injured. The inventive cutting device is arranged essentially midway between the conveyor chains 6, indicated by dashed lines in Fig. 5. The pivot arm 21 and the wheels 20 are arranged in a channel structure 24, while the cylinder 16 and the cutting blade 15 are mounted on a bracket 25 suspended from the channel structure 24. An upper protec- tive hood 26 serves to protect the device and has an open¬ ing through which the cutting blade 15 can be projected. To enable the cutting blade to be projected at high speed, the pneumatic cylinder is suitably of a type having a thick piston rod, so that only an insignificant amount of air has to be evacuated from the top side of the piston when the cutting blade is projected. To make it possible to cut off the wrapping strings while the bale is at the same time continuously moved, the cutting blade must, immediately after being projected, be returned to the starting position, which is done by the control circuit switching, via an air valve, the air pressure from the underside of the cylinder piston to the top side thereof. The air pressure is preferably switched before the cutting blade has reached its upper end position, so that the blade is slowed down comparatively gently. It goes without saying that the invention may be modified in many ways within the scope of the appended claims. For instance, the path of movement of the cutting blade 15 need not be linear and perpendicular to the plane of conveyance of the articles, and the blade need not necessarily be projected by a pneumatic cylinder. Further, the sensor 19 does not have to be arranged in front of the cutting blade 15 against the direction of conveyance, but the sensor and the blade may be arranged parallel to each other, in which case the blade can be projected without delay. Naturally, the invention is not restricted to the cutting of metallic wrapping strings. If another sensor is used, wrapping strings of other materials can be sensed and cut off. Instead of a single string-removing station where the bales of pulp are turned through 90°, backed through the station and again conveyed through the station for removal of the wrapping strings extending perpendicu¬ lar to the first strings, as described in the foregoing, use can be made of two successive stations, making it possible to remove the strings from the bales during continuous conveyance thereof, with no time-consuming stoppages.

Claims: CLAIMS 1. A device for cutting off wrapping strings or bands on wrapped articles, such as bales of pulp (1), comprising a cutting-edge holder (15) which, from a first inoperative position located outside a boundary surface of a separate article, can be projected at high speed towards said article to a second position in which the cutting edge is located at least in the same plane as the boundary surface of the article while cutting off a separate wrapping string on the article, c h a r a c t e r i s e d in that the cutting-edge holder (15) is located beneath the article, more precisely between two endless conveyor elements or chains (6), so that the wrapping string (4), when cut off, will be retained in position by being squeezed between the article and each of the conveyor chains, and that the device has a sensor (19) for sensing, while the article is moving in the longitudinal direction in relation to the device, the position of a separate wrapping string (4) and causing the cutting-edge holder (15) to project towards the article in order to cut off the wrapping string when this crosses the path of movement of the cutting-edge holder. 2. A device as set forth in claim 1, c h a r a c - t e r i s e d in that it is located beneath a plane of conveyance (17) of the wrapped articles (1) . 3. A device as set forth in claim 1 or 2, c h a ¬ r a c t e r i s e d in that the path of movement of the cutting-edge holder (15) is linear. 4. A device as set forth in any one of the preceding claims, c h a r a c t e r i s e d in that the cutting- edge holder (15) has a linear cutting edge (18) extending in parallel with the direction of movement of the articles (1). 5. A device as set forth in any one of the preceding claims, c h a r a c t e r i s e d in that the sensor (19) is located in front of the cutting-edge holder (15), as seen in the direction of movement of the articles (1), the cutting-edge holder (15) being projected with delay after the sensor has sensed the presence of a wrapping string (4). 6. A device as set forth in any one of the preceding claims, c h a r a c t e r i s e d in that the sensor (19) is an inductive sensor for sensing metallic wrapping strings (4) . 7. A device as set forth in any one of the preceding claims, c h a r a c t e r i s e d in that it comprises a blocking means (20, 21, 23) which has to be activated to enable the projection of the cutting-edge holder (15). 8. A device as set forth in claim 7, c h a r a c ¬ t e r i s e d in that the blocking means comprises two rotatable, spaced-apart wheels (20) which have concentric axes of rotation and which are resiliently applied against the article (1). 9. A device as set forth in claim 8, c h a r a c ¬ t e r i s e d in that the sensor (19) is located in the area between the wheels (20). 10. A device as set forth in claim 8 or 9, c h a ¬ r a c t e r i s e d in that the path of movement of the cutting-edge holder (15) extends through the space between the wheels (20).

Inventors: GRAHN PER-ARNE, GRAHN, PER-ARNE
Applicants: CONPAP AB
Application year: 1993
Main classification: B65B69
IPC codes: B65B69