Bag slitting machine

Abstract: A machine (1) for slitting filled bags (2), incorporates saw means (8), and displacement means (9) to cause relative movement between the saw means (8) and a bag (2) to be slit, the saw means (8) comprising a blade (10) in which a cutting section (11) of the blade (10) is located orthogonally with respect to the direction of relative movement such that the cutting section (11) penetrates a leading end (3) of the bag (2) and, during continued relative movement, cuts through both the bag contents and the bag sides (5), towards the trailing end (4) of the bag (2).

Description: This invention relates to a bag slitting machine for the slitting and emptying of bags containing products such as asbestos, cement, grain, etc. Known machines are described in GB 0198685, GB 1315853, GB 2060545, GB 2092980 and US 3853235. Previous systems have usually employed a pair of circular cutting blades or saws adapted firstly to form a cut in one end of the bag and secondly to continue the cut individually along each lateral side of the bag, and this cutting technique has required a specialised conveyor means capable of driving the bag along the cutters, and hence has usually required the use of a spiked chain conveyor to engage the bag to provide for positive drive of the bag through the cutters. In FR-A-1547391 is disclosed a bag slitting machine in which the bags are slit into two halves by means of a band saw which, by its very presence within the bag during slitting, also has some bag splitting effect to encourage discharge of the bag contents, with the splitting completed by the two separated bag halves being carried on the spikes of rollers rotatable about parallel axes. The band saw, and specifically its slitting section, are statically positioned with respect to the slitting machine, so that the slitting section is constantly in an effective slitting position. The present invention provides a machine which departs from this conventional cutting technique, and yet which achieves not only rapid bag cutting and hence contents discharge, but also machine production cost reduction. According to the present invention, there is provided a machine for slitting filled bags, as defined in Claim 1. Although the relative movement could be effected by displacing the saw means, with the bag static, preferably the bag is displaced with respect to a statically positioned saw means. Such bag displacement means conveniently comprises a conveyor means (such as a relatively cheap belt conveyor, or a relatively expensive spiked conveyor with retractable spikes) or the convex periphery of a feed roller; or a gravity chute (either vertical or inclined). The saw means preferably takes the form of a band saw, although a reciprocating blade saw means could be used. Beyond the saw means, the machine is preferably provided with support means, such as a plurality of bars, for temporarily supporting the upper part of a partially or wholly slit bag. Some embodiments of the machine would also benefit from the presence of bag guide bars to guide the lower part of the bag downwardly and hence assist in exposing the bag contents for efficient emptying. With a belt conveyor, downward movement of the lower part of the bag may be effected by providing a plurality of discs (which may be freely rotatable or driven in the opposite direction to the conveyor) adjacent the discharge end of the belt conveyor, to define a nip capable of gripping firstly the lower part of a partially slit bag and then eventually the upper part of the bag until the entire bag has been passed, in an emptied condition, through the nip. With a vertical gravity chute, a nip may be defined between an array of bag guide bars beyond the saw means, and a roller with retractable spikes, the periphery of the roller being appropriately spaced from the guide bars to define a nip through which firstly the lower part of a partially slit bag and then eventually the upper part of the bag is dragged by the spikes until the entire bag has been passed, in an emptied condition, through the nip. With a feed roller this may form part of a feed screw, with the bags fed laterally on to the top of the feed screw, to constitute a combined feed roller and screw. With this last mentioned arrangement a nip roller may be provided adjacent the screw, again to define a nip into which a slit bag is pulled firstly by its lower part, and then by its upper part. Irrespective of the various possibilities of feed arrangement, the slit bags may, if required, be allowed to fall into a rotatable, wire mesh emptying cage in which the bags are retained, for later removal, with any remaining bag contents adapted to fall from the cage onto suitable conveying or storage means. With a belt conveyor, this may be horizontal or inclined, depending on the materials of the belt and of the bags and hence the coefficient of friction and the force required to drive a bag into the saw means. In accordance with a preferred technique cutting is halted shortly before the blade reaches the trailing end of the bag. This may be achieved by any of various means, such as by employing sensing means to detect the trailing end, and possibly also the leading end, of a bag, and upon detection of the trailing end, to activate a movable, e.g. pivotable, obstruction means, such as the advanceable and retractable splitter bar referred to earlier to displace the latter to a position in advance of the blade thus to obstruct further bag advance so that the part slit bag may be pulled from the conveying means, e.g. by the technique described in GB 0198685 for bag emptying purposes, or for completion of bag emptying. In an alternative manner of achieving this effect, the cutting action of the blade may be stopped and, with a diamond coated blade for instance, which, in contrast to a conventional, reciprocable blade, would not be provided with a serrated tooth edge, and hence would not form a cutting edge, so that by stopping such a blade, the blade itself acts as an obstruction means and the upper part of a part-slit bag would automatically start to feed in the reverse direction over the top of the blade. In accordance with another possibility, it will be appreciated that cutting can be effected completely through the bag from its leading end to its trailing end, so that an upper part of the bag is completely separated from a lower part of the bag. The invention will now be further described in greater detail, by way of examples, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a first embodiment of machine; Figure 2 is a side elevation of Figure 1; Figure 3 corresponds to Figure 1 but shows a second embodiment of machine; and Figures 4 and 5 are side elevations of Figure 3, showing two different operational positions. In all embodiments, like components are accorded like reference numerals. A machine 1 is provided for slitting filled bags 2, of industry-standard profiles, forms and capacities such as paper bags or hessian sacks, each bag 2 comprising a leading end 3, a trailing end 4, lateral sides 5 and, after slitting as will be described later, an upper part 6 and a lower part 7. The machine 1 incorporates saw means 8 and displacement means 9 to cause relative movement between the saw means 8 and the bag 2 to be slit. The saw means 8 preferably comprises band saw having an endless band 10 in which a cutting section 11 is located orthogonally with respect to the direction of relative movement, and which as illustrated is orthogonal to the longitudinal axis of the bag 2 such that the cutting section 11 penetrates the leading bag end 3 and, during continued relative movement cuts through both the bag contents and the bag sides 5, towards the trailing end 4 of the bag 2. Relative movement between the bag 2 and saw means 8 is preferably effected by displacing the bag 2 with respect to a statically positioned saw means 8. For this purpose the bag displacement means 9 may be constituted by a conveyor means, specifically a belt conveyor 13, with an associated chute 14 and a feed roller/screw 15 in the embodiment of Figures 1 and 2. In the embodiment of Figures 3 to 5 the belt conveyor 13 has an upper belt run 16 onto which bags 2 to be slit are loaded by any convenient means - normally manually or mechanically - the conveyor having a head drum 12 and a tail drum 18. Beyond the saw means 8, the machine 1 is provided with support means in the form of a plurality of parallel bars 21 for temporarily supporting the upper part 6 of the bag 2. In Figures 1 and 2 a nip 23 is defined between roller means 27 and the feed roller/screw 15, through which nip 23 the slit bag is progressively pulled, beginning with its lower part 7, as Figure 2 indicates. The saw means 8, in both embodiments, has the band 10 extending, under suitable tension, between a drive pulley 28 and a return pulley 29 with the cutting section 11 of length exceeding the width of the bags 2. The pullies 28 and 29 may be rotatable about horizontal axes 30 (Figures 3 and 4), or inclined axes 32 (Figures 1 and 2), while the diameters of the pullies 28 and 29 may be such that equipment may be located within the saw means 8. In Figure 2 is indicated a simple pendulum type sensor 34 for sensing the presence of the trailing end 4 of the bag 2, whereupon the sensor 34 falls, clockwise, to the position indicated in dotted line. This sensor movement may be employed to trigger a control system (not shown) to stop the drive to pulley 28 and hence to stop the cutting action of the band 10. With the latter being of the diamond coated type, the cutting section 11 thereafter acts additionally as a splitter means to progressively penetrate the slit bag 2 and then to act as an obstruction means to prevent further bag advance and hence also, as the cutting action is stopped, to prevent the upper bag part 6 being completely separated from the lower bag part 7. Progressive separation of the upper and lower parts 6 and 7 is ensured, as slitting proceeds along the bag by the bag being displaced past the cutting section 11 of the band 10, by the presence in the embodiment of Figures 1 and 2 of a splitter bar 35, which is supported from link arms 36 swingable between a non-active position within the band 10, and an active position shown in dotted line, under the control of a bag end sensor 34, ahead of the cutting section 11, to halt further bag displacement. Figures 3 to 5 indicate that the cutting section 11 of the band 10 may additionally function as a splitter means, with sensing of the trailing end 4 of the bag 2 swinging the entire saw means 8 about the axis 37 from the cutting position illustrated in Figure 4 (where the cutting section 11 additionally functions as a splitter bar), to the slit bag release position illustrated in Figure 5, and also illustrated in dotted line in Figure 3. Figure 3 also indicates that the belt conveyor 13 can comprise a plurality of individual and mutually spaced-apart belts 38.

Claims: A machine (1) for slitting filled bags (2), incorporating: saw means (8) to effect slitting; displacement means (9,14) to cause progressive relative movement between the saw means (8) and a bag (2) to be slit; a splitter means (35,11) located transversely of the direction of relative movement, to progressively penetrate the slit bag (2) to ensure progressive separation of the slit bag (2); characterised in that means (21,37) is provided to advance said splitter means (35,11) to an active position and to retract said splitter means (35,11) to a non-active position. A machine as claimed in Claim 1, characterised in that the displacement means is effective on the saw means (8) to displace the saw means (8), with the bag (2) remaining static. A machine as claimed in Claim 1, characterised in that the displacement means (9) is effective on the bag (2), with the saw means (8) statically positioned. A machine as claimed in Claim 3, characterised in that the bag displacement means (9) comprises a conveyor means. A machine as claimed in Claim 4, characterised in that the conveyor means is a belt conveyor (13). A machine as claimed in Claim 4, characterised in that the conveyor means is a spiked conveyor with retractable spikes. A machine as claimed in Claim 3, characterised in that the displacement means (9) comprises a gravity chute (14). A machine as claimed in Claim 7, characterised in that the chute (14) is vertical. A machine as claimed in Claim 7, characterised in that the chute (14) is inclined. A machine as claimed in any preceding Claim, characterised in that the saw means (8) takes the form of a band saw (10). A machine as claimed in any one of Claims 1 to 9, characterised in that the saw means (8) takes the form of a reciprocating blade saw means. A machine as claimed in Claim 4, characterised in that the conveyor means is constituted by the convex periphery of a feed roller (15). A machine as claimed in Claim 12, characterised in that the feed roller (15) forms part of a feed screw. A machine as claimed in Claim 13, characterised in that a nip roller (27) is provided adjacent the feed roller screw (15), to define a nip (23) into which a slit bag (2) is pulled. A machine as claimed in any preceding Claim, characterised in that a rotatable, wire mesh emptying cage is provided, in which cage slit bags (2) are retained, for later removal, with the bag contents adapted to fall from the cage onto a suitable conveying or storage means. A machine as claimed in any preceding Claim, characterised in that the splitter means is constituted by a transverse splitter bar (35). A machine as claimed in any one of Claims 1 to 15 characterised in that the splitter means is constituted by the cutting section (11) of the blade (10) of the saw means (8). A machine as claimed in any preceding Claim, characterised in that there is provided, beyond the saw means, in the direction of relative movement, support means (21) for temporarily supporting the upper part (6) of a partially or wholly slit bag (2). A machine as claimed in any preceding Claim, characterised in that sensing means (34) is provided for detecting the trailing end (4) of a bag (2). A machine as claimed in any preceding Claim, characterised in that sensing means is provided for detecting the leading end (3) of a bag (2). A machine as claimed in Claim 19, characterised in that an output from the sensing means (34) upon the trailing bag end (4) being sensed is connected to a control system to activate splitter means (35,11). A machine as claimed in Claim 21, characterised in that the splitter means (35,11) is pivotal between an active position and a non-active position under control of the sensing means (34).

Inventors: BENNISON STEWART C O PALAMATIC, BENNISON, STEWART, C/O PALAMATIC HAND. SYS. LTD.
Applicants: PALAMATIC HANDLING SYST, PALAMATIC HANDLING SYSTEMS LIMITED
Application year: 1991
Main classification: B65B69
IPC codes: B65B61, B65B69, B23D53