GB2032380A - Filling sacks with particulate material - Google Patents

Abstract

Sacks (10) are filed with particulate material by inserting a rigid filling nozzle (22) into an inlet at the top of the sack (there being no other opening at the top), the nozzle having an air venting passage (34) restricted (40) to control the air outflow and thereby minimise entrainment of material. The nozzle discharges the material downwardly and the inlet (36) to the venting passage is located above the discharge outlet (24). <IMAGE>

Description

SPECIFICATION Filling sacks with particulate material This invention relates to filling powdered or granulated solids into bags or sacks (herein referred to generally as sacks), and is especially applicable to filling plastics sacks having a self-closing valve.

Sacks of the foregoing type are usually made in the shape of a non-rigid closed rectangular box, and have a tubular sleeve of flexible material in one corner, which opens into the interior of the sack. This sleeve is the only opening into the sack, and is arranged so that when a sack is filled the sleeve is flattened and acts as a valve.

The filling of plastics sacks of this kind is generally carried out using a rigid tubular horizontal filling nozzle through which the material is discharged into the sack from an elevated feed hopper or similar storage receptacle, usually under slight pressure. A sack to be filled is placed with its inlet sleeve fitted over the filling nozzle, the sack being suspended from the nozzle. There may be an inflatable cuff around the nozzle, which is inflated so as to seal the gap between the nozzle and the sleeve. When sacks were made of paper, there was usually sufficient porosity in the paper, or slight leakage through the seams, to relieve the air displaced by the particulate material. Also, since the paper was substantially inelastic, there was no expansion of the sack.Thus, paper sacks could usually be filled in this manner without much difficulty, and assume a generally rectangular shape suitable for stacking in layers.

When such sacks are made of plastics film instead of paper, however, the lack of porosity in the film, and its semi-elastic nature, result in air having difficulty in escaping, so that the sack tends to inflate, and excessive pressure can cause deformation of the sack. The filled sacks, therefore, frequently resemble resilient cushions, and have a rather rounded shape.

This is wasteful of space, and does not lend itself to easy or safe multiple stacking of such sacks.

The present invention provides a method of filling a sack with particulate material, which comprises inserting a filling nozzle into an inlet opening at the top of the sack, the sack having no other opening at the top, the nozzle having an air venting passage extending from its inner end to a region outside the sack, and discharging the particulate material into the sack through said nozzle, the venting tube being of restricted cross-section such that the flow of air being vented is insufficient to entrain enough of the particulate material to block the air venting tube.

The sack is preferably of plastics material. The inlet opening may be provided with a sleeve which extends into the interior of a sack and into which sleeve the nozzle is inserted, the sleeve being flattened by the pressure of the contents when the sack is filled. The inner end of the air venting tube preferably opens adjacent the top of the inner end of the nozzle, so that it lies above the maximum level to which the material rises in the sack. Two or more air venting tubes may be provided if desired. The air venting tube may be provided with means for restricting the flow of air, the restriction means being adjustable or interchangeable with other such means so as to provide a different degree of restriction.

In order that the invention may be more clearly understood, various embodiments will now be described with reference to the accompanying drawings, wherein: Fig. 1 shows a plan view of an empty sack laid flat, Fig. 2 shows the manner in which the sack is fitted onto the filling nozzle, Fig. 3 shows a perspective view of a filled sack laid flat, Fig. 4 shows a perspective view of one embodiment of filling nozzle of the present invention, Fig. 5 shows a perspective view of a second embodiment of filling nozzle of the present invention, Fig. 6 shows a longitudinal cross-sectional view through the filling nozzle of Fig. 5, and Fig. 7 shows a transverse cross-sectional view through the filling nozzle of Figs. 5 and 6; Referring to the drawings, and firstly to Figs. 1 to 3; a sack 10 is made up from flexible sheet material in the shape of a non-rigid closed rectangular box, as clearly seen in Figs. 2 and-3. When empty, the sack can be folded flat as shown in Fig. 1, with the top and bottom panels 12, 14 respectively being folded over into the same plane as the side panels 16. An inlet opening is provided in a top corner of the sack, and a flexible sleeve 18 is sealed into this opening so that the inner end of the sleeve opens into the sack. The outer end of the sleeve may terminate flush with the side wall of the sack, or, as shown in Figs. 1 to 3, it may project some distance beyond the side wall of the sack.

A hopper 20 for particulate material (only the bottom part of the hopper is shown in Fig. 2) is provided with a horizontal filling nozzle 22 at its discharge end, the free end of the nozzle being generally rounded but with a downwardly opening discharge outlet 24. The sleeve 18 of a sack 10 to be filled is fitted over the nozzle 24 so that the nozzle extends along the top of the sack. The sack is thus suspended from the nozzle. A conventional sack filling nozzle may be provided with an inflatable cuff, which is then inflated to seal the space between the sleeve and the nozzle. However, nozzles of the present invention do not have such inflatable cuffs (or at any rate the cuffs do not need to be inflated in carrying out the process of the present invention).The particulate material, usually under slight positive pressure, is discharged from the hopper through the nozzle and into the sack. When the sack is full the flow of material is stopped and the filled sack is removed from the nozzle. Before the sack is removed a jet of compressed air may be directed into the nozzle to clear any material lodging therein into the sack. On removal from the nozzle, the pressure of the contents of the sack causes the tubular sleeve to flatten and effectively close the sack. As shown in Fig. 3, the projecting end of the sleeve can then be folded to lie against the side wall of the sack, and secured there if desired.

Referring to Fig 4; this embodiment of nozzle 22 for carrying out the process of the present invention has the same form as that illustrated in Fig. 2, but is provided with a pair of air venting tubes 26. These can conveniently be constructed from a tube cut in half lengthwise to form semi-circular channels which are welded onto each side of the nozzle 22 near the top of the nozzle; that is so that the openings 28 to the air venting tubes are at the inner end of the nozzle and generally above the discharge outlet 24. The air venting tubes extend along the nozzle to a point which will lie outside the sack, and can either terminate at that point or can lead through conduits to a suitable discharge zone for the vented air (for example a dust collection system).The outer end of the nozzle is mounted to an adaptor plate 30 by means of which it is secured to the outlet of the hopper 20.

Using such a nozzle, plastics sacks can be filled, for example with pelleted carbon black, without any tendency to balloon and, providing the outside contours and surface finish of the nozzle are suitably smooth and the sleeve 18 of the sack and the filling nozzle are dimensionally matched, the fitting of the empty sacks and removal of the filled sacks can be accomplished without difficulty, and the whole operation conducted with greater speed and efficiency than has generally been the case hitherto. The effect of the weight of material entering the sack is to squeeze the suspended sack to a minimum size with no excess air trapped inside, so that on removal of the filled sack this readily takes up the desired shape as indicated in Fig. 3.

The cross-sectional area of the venting passages is arranged so as to provide some restriction on the rate of flow of air, so that the escaping air does not entrain too much of the particulate material, and result in the passages becoming blocked. Instead of controlling the dimensions of the air venting passages themselves, the same effect can be achieved by restricting the flow of venting air by means of a valve or a restricted orifice at the outlet end of each venting passage. Apart from avoiding blockages of the venting passages, the controlled escape of venting air limits the escape of the material, particularly in the case of dusty materials, and therefore limits the extent of pollution and wastage.

It is desirable that the filling spout should be readily removable, for example by dismounting the adaptor plate 30 from the hopper, so that a range of interchangeable filling nozzles can be used with different air venting rates according to the materials to be filled in the sacks. This interchangeability also enables sacks having different sizes of inlet sleeves to be accommodated. Where the inlet sleeve is of a standard size, then a single filling nozzle with an adjustable or interchangeable air venting restrictor may be preferred.Another advantage of using a specific air venting arrangement, as in the present invention, is that any escaping material, particularly in the case of dusty materials, will be almost exclusively confined to that which may be entrained in the venting air, and hence an anti-pollution dust collecting system can be localised at the outlet of the vent ing passage, whereas at present extensive dust col lecting systems with suction hoods have to be arranged overthe entire filling region. The cleanli ness of the whole system is thereby likely to be improved using the present invention.

It should also be noted that, although particularly intended for use with plastic sacks, the improved process and filling nozzle of the present invention can advantageously be used with conventional paper sacks having self-closing inlets. Again, an inflatable cuff around the nozzle is unnecessary in such cases. The better venting and elimination of trapped air allows more rapid handling than when using a conventional filling nozzle.

Figs. 5 to 7 show an alternative design of filling nozzle in which the desirable circular external cross-section is retained. In this case, the nozzle 22 (see Fig. 6) has essentially the same shape as the nozzle shown in Figs. 2 and 4. However, it is surrounded by a second circular tube 32 of larger diameter, but of generally similar configuration. The discharge openings 24 of the two tubes 22, 32 have the same size and shape, and are coincident as can be seen in Figs. 5 and 6; the two tubes preferably being welded together around the edges of this opening. The tube 22 is located eccentrically within the tube 32 so that they are in contact along the bottom but spaced apart along the top region, as can be seen clearly in Figs. 6 and 7, thereby providing a crescent-shaped air venting passage 34. The inlet to this air venting passage is provided by a small orifice 36 in the rounded inner end region of the tube 32 above the discharge opening 24. The outlet from the passage 34 is provided by an upstanding spigot 38 which is externally screw-threaded for connection to a further venting conduit or, as shown in Fig. 6, to an air flow restrictor 40. The restrictor 40 can be interchanged with other restrictors which provide different degrees of restriction on the air flow. If the spigot 38 is connected to a further air venting conduit, suitable airflow restrictor means can be provided in that conduit.

Figs. 4 to 7 show just two of a large number of possible different arrangements of air venting passage on a filling nozzle of the general type shown in Fig. 2.

Claims (13)

1. A method of filling a sack with particulate material, which comprises inserting a filling nozzle into an inlet opening at the top of the sack, the sack having no other opening at the top, the nozzle having an air venting passage extending from its inner end to a region outside the sack, and discharging the particulate material into the sack through said nozzle, the venting passage being of restricted cross-section such that the flow of air being vented is insufficient to entrain enough of the particulate material to block the air venting passage.

2. A method according to claim 1 wherein the sack is of flexible plastics material.

3. A method according to claim 1 or claim 2 wherein the inlet opening is provided with a sleeve which extends into the interior of a sack and into which sleeve the nozzle is inserted, the sleeve being flattened by the pressure of the contents when the sack is filled.

4. A method according to any one of the preceding claims wherein the inner end of the air venting passage opens adjacent the top of the inner end of the nozzle, so that it lies above the maximum level to which the material rises in the sack.

5. A method according to any one of the preceding claims wherein the air venting passage is provided with means for restricting the flow of air, the restriction means being adjustable or interchangeable with other such means so as to provide a different degree of restriction.

6. A method of filling a sack with particulate material substantially as described herein with reference to the accompanying drawings.

7. Afilling nozzle for use with a method of any one of the preceding claims, the nozzle comprising a rigid elongate tube having an inlet for particulate material at one end and an outlet for the material at the other end, the outlet being substantially to one side of the longitudinal axis of the nozzle, the nozzle having an air venting passage extending from the particulate material outlet end region to a point from which air can be discharged externally of the sack, the inlet to the air venting passage being located substantially on the opposite side of the longitudinal axis of the nozzle to the particulate material outlet.

8. A nozzle according to claim 7 wherein the particulate material outlet end of the nozzle is generally rounded to assist its insertion into a sack.

9. A nozzle according to claim 7 or claim 8 wherein the air venting tube is provided with means for restricting the flow of air, the restriction means being adjustable or interchangeable with other such means so as to provide a different degree of restriction.

10. A nozzle according to any one of claims 7,8 and 9 comprising two tubes located eccentrically one inside the other, the inner tube being for passage of particulate material, and the crescent-section space between the two tubes providing the air venting passage.

11. A filling nozzle substantially as described herein with reference to the accompanying drawings.

12. A machine for filling sacks with particulate material, the machine comprising a horizontal rigid filling nozzle for insertion into an inlet opening at the top of a sack, the nozzle having an air venting passage extending from its inner end to a region outside the sack, and means for supplying particulate material to the nozzle for discharge into the sack, the nozzle being arranged to discharge the particulate material downwardly into the'sack, the air venting passage having an inlet substantially above the particulate material discharge opening of the nozzle.

13. A machine according to claim 12 wherein the nozzle is in accordance with any one of claims 7 to 10.