A CONVEYOR APPARATUS

Abstract: A conveyor apparatus is designed for the transport of small parts, but also for the transport of elongate, continuous material pieces such as film strips (9), fibres or the like, and comprises an ejector, with a main channel (3) into which discharge aspiration means (2, 11) for air. According to the invention, the main channel (3) has a straight and interiorly smooth portion. The aspiration means include a side channel (2) with a nozzle (11) coaxially disposed therein. The side channel, which is straight and cylindrical, is connected to a connection (10) in the wall of the main channel, the nozzle being located radially outside the cross-section of the main channel and being placed and directed such that the centre axis (13) of the nozzle and the centre axis (14) of the main channel disect one another at an acute angle, preferably approximately 22<o>, at a point located downstream of the opening. Downstream of the opening (10), the main channel (3) has a straight portion, whose length is from 5 to 8 times its diameter.

Description: TITLE OF INVENTION A CONVEYOR APPARATUS TECHNICAL FIELD The present invention relates to a conveyor apparatus which is primarily intended for the conveyance or transport of light plastic material, such as film strips or the like, but which, naturally, may also be employed for the conveyance of small details, and which is designed as an ejector with a main channel into which discharges means for the aspiration of a driving gas under pressure. BACKG3R00ND ART It is previously known to convey or transport different forms of material such as grain, plastic granulate, flocks and fibres etc. in conduits in which an air current carrying the material is employed. It is also previously known to employ ejectors for advancing the air current which carries the transported material in the con¬ duit. When demands for large transport capacity are raised, this entails that very great air volumes must be set in motion in the conduit. When the transported material finally arrives at the end of the conduit, this large volume of air must be separated-off from the transported material. If, in such an instance, the transported material is light in weight or consists of particles of different sizes and weights, the air separation operation may cause con¬ siderable problems which are aggravated the greater the volume of air. For example, these problems may reside in the fact that lighter fractions of the transported material give off dust and are set in vortex, and that the transported material is subjected to a pressure which is dependant upon the flow speeds and rates, mat¬ erial transport rates and the like in the conduit and the apparatus which is subsequently employed for separation of the air. In such a case, the separated material may, hence, be under a pressure which varies with time when it is discharged from the separator which, in many practical situations, may consist of a cyclone. Naturally, large air volumes also entail a waste of energy and heat losses if the conveyance takes place from a heated space to a cooler space. HϊOBLEM S-CRϋCTDRE Thus, the object of the present invention is to realise a con¬ veyor apparatus which, using a minimal volume of air, permits max¬ imum transport capacity, at the same time as the conveyor apparatus is designed so as to make for the transport of small details but also of elongate, continuous material pieces, such as fim strips, fibres and the like. SOLUTION This object is attained according to the present invention if the conveyor apparatus disclosed by way of introduction is chara¬ cterised in that the main channel has a straight and substantially cylindrical portion which is interiorly smooth; that means for the aspiration of the gas include a nozzle which is located at an open¬ ing in the wall of the main channel and radially outside the main channel, a centre line through the nozzle making an acute angle with a centre line of the main channel. According to the present invention, it also suitably applies that the nozzle is disposed in a side channel whose termination to¬ wards the main channel covers the opening thereof; and that the nozzle is directed and placed such that the point of disection be¬ tween the centre line of the nozzle and the centre line of the main channel will be located downstream of the opening. One embodiment of the present invention which is particularly simple in manufacture is characterised in that the side channel accommodating the nozzle is substantially straight and cylindrical, the nozzle being coaxial therewith. in order to guarantee the good efficiency of the conveyor ap¬ paratus as regards taking in new material, at the same time as the discharge speed from the discharge end of the conveyor apparatus is made as low as possible, the subject matter of the present in¬ vention is also characterised in that the main channel has, on its upstream side, an inlet channel of substantially the same diameter as the main channel; and that the main channel has a broadened portion a distance downstream of the opening. In order to permit a further reduction of the volume of air passing through the conveyor apparatus without any appreciable re¬ duction of its transport capacity, the present invention further calls for the provision of a throttle in the inlet channel, prefer¬ ably at its intake. An optimated embodiment of the present in¬ vention is characterised in that the throat cross-sectional area of the nozzle constitutes approximately 4% of the cross-sectional area of the main channel, and that the angle between the centre line of the nozzle and the centre line of the main channel lies in the ra¬ nge of between 20 and 25°. It further suitably applies that the length of the main channel between the broadened portion and the nozzle lies in the order of magnitude of from 5 to 8 times its dia¬ meter. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The nature of the present invention and its aspects will be more readily understood from the following brief description of the accompanying Drawings, and discussion relating thereto. In the accompanying Drawings: Fig. 1 is a schematic illustration of the conveyor apparatus according to the present invention; and Fig. 2 is a simplified cross-section through an ejector ap¬ paratus included in the present invention. DESCRIPTION OF PREFERRED EMBODIMENT The invention is generally based on the concept that an air jet of slight volume flow and relatively low pressure but high spe¬ ed shall flow in the longitudinal direction of a relatively slim- lined, preferably straight and interiorly smooth conduit for ac¬ celerating the material flow therethrough. The low volume flow but high flow speed of the driving jet entails that the total volume flow of air passing through the conveyor apparatus will be small while nevertheless not negatively affecting the transport capacity. Tfc will be apparent to the skilled reader of Fig. 1 that the conveyor apparatus according to the present invention includes a high-pressure fan or a compressor 1, which, by the intermediary of a side channel 2, is connected to a main channel 3 in the conveyor apparatus. The main channel consists of an interiorly smooth, sub¬ stantially cylindrical and straight tube which, on the downstream side of the side channel, has a broadened portion 4, there being subsequently connected thereto a conveyor conduit 5 of sub¬ stantially the same diameter as the larger end of the broadened portion. The length of the transport conduit 5 may be selected op¬ tionally and may, thereby, be adapted to meet the demands which are placed in each individual case. Suitably, the ratio between the diameter of the transport conduit 5 and the main channel 3 is ap¬ proximately 4:3. On the upstream side of -the main channel 3, the conveyor ap¬ paratus is provided with an inlet conduit 6 with an intake device 7. In the embodiment shown on the Drawings, the intake device 7 is designed for the infeed of film strips which may be the residual product of the manufacture of plastic film. To this end, the intake device is provided with two rolls 8 which are employed for the in¬ feed of the two film strips 9. Furthermore, the rolls 8 are ar¬ ranged in such a manner in the intake device 7 so as to form a throttle, which entails a relatively high flow speed between the rolls, whereby the infeed capacity will be improved, at the same time as the air volume which passes in through the intake device is reduced. It has proved in practice that the- inlet conduit 6 should be of substantially the same inner diameter as the main channel 3, and that a very powerful throttle can be accepted in the intake device 7. Fig. 2 shows a diametric longitudinal section through the main channel 3 and the side channel 2 connecting thereto. It will be ap¬ parent from the Drawing that the main channel 3 consists of a cy¬ lindrical tube with a completely smooth inner side surface. The main channel has " , further, an opening 10 which is designed and di¬ mensioned so as to connect to the inner surface in the side channel 2, at least along the downstream half of the connection between the side channel 2 and the main channel 3. -interiorly in the side channel 2, there is disposed a nozzle 11 which is located cer 1 -rally in the side channel and is directed coaxially therewith. It should, here, be observed that the side channel 2 is of uniform thickness throughout its length, for which reason there will be formed a chamber or free space downstream of the opening 12 of the nozzle, so that the air jet departing from the opening may freely pass therethrough without impinging upon its walls or being affected thereby. In the illustrated embodiment, the nozzle is, furthermore, designed as an approximately frusto-conical funnel which, at its throat portion or opening 12, is once again broadened somewhat, preferably by a conical flaring with a top an¬ gle of approximately 30°. The nozzle 11 is fixedly retained in the outer portion of the side channel 2 and has a completely smooth transition interiorly to the inner surface of the side channel and may, possibly, be adjustable in the longitudinal direction of the side channel for purposes of operational opti ation. It will be further apparent from Fig. 2 that the nozzle 11 is located completely outside the cross-sectional area of the main channel 3, for which reason the nozzle 11 can, per se, never der- ange or influence the passage of material or air being transported through the main channel. Moreover, the nozzle is located centrally in the side channel 2 at its region of connection to the main chan¬ nel 3 at the opening 10. Hereby, the nozzle will, as a result of the free space there formed, emit an air jet which is not ap- preciably influenced by the walls of the side channel 2, nor yet by the edges of the main channel 3 defining the opening 10, as a re¬ sult of which the jet departing from the nozzle can be considered as a substantially concentrated free jet which is deflected so as gently to follow the longitudiunal direction of the main channel and there give rise to a flow pattern or field of very high flow speed, at least in the central portions of the main channel 3. Preferably, the outlet of the fan is connected directly to the connecting flange of the side channel 2, as shown in Fig. 2, for which reason the conduit between the fan 1 and the nozzle 11 is of uniform thickness - and also straight - throughout its entire len¬ gth. This results in very slight flow losses. Furthermore, the side channel 2 is of large inner diameter in relation to the nozzle op¬ ening 12 (approximately 350%), which also contributes to reducing the flow losses. However, it is more important that the flow speed (which is already relatively high at the fan outlet) is very gre¬ atly magnified in the nozzle, as a result of which the turbulence which unavoidably occurs at the fan outlet is severely suppressed consequential upon the speed increase, so that the air jet de¬ parting from the nozzle opening 12 may be considered as turbulence- -free. Practical tests have shown that that angle which is made bet¬ ween the centre line 13 of the nozzle 11 and the side channel 2, and the centre line 14 of the main channel has considerable influ¬ ence on the efficiency of the conveyor apparatus. Thus, it has pro- ved that this angle should lie in the range of from 20 to 25°, a marked efficiency maximum being attained at approximately 22°. Even very slight deviations (1-2°) from this optimum value results in a drastic reduction in efficiency. It is probably the case that if the angle is reduced, the jet departing from the nozzle will im- pinge against the edge of the opening 10 or the upper defining wall (shown in Fig. 2) of the main channel 3, with considerable tur- bulance as a result. If, on the contrary, the angle is increased, the jet departing from the nozzle will instead impinge on the lower edge of the main channel 3 in Fig. 2, at a relatively obtuse angle, which will also result in turbulence and diffusion of the jet. As has been mentioned above, the angle of disection between the centre axes 13 and 14, respectively, of the side channel 2 and the main channel 3, should be 22°. In the event the edge of the downstream-located portion of the opening 10 coincide with the in- ner defining surface of the side channel 2 in the region of con¬ nection with the main channel, this entails that the two centre ax¬ es 13 and 14 should disect one another downstream of the opening 10, and more precisely a distance which amounts to approximately one third of the inner diameter of the main channel, or scarcely half of the inner diameter of the side channel. The location of the nozzle opening 12 along the centre axis 13 of the ' side channel 2 is also of great importance to the efficiency of the apparatus. As has been mentioned above, the nozzle 11 must, in its entirety, be placed outside the cross-sectional area of the main channel 3. The conical angle in the nozzle may vary, but the opening 12 of the nozzle must lie in a plane at right angles to the centre axis 13 and be placed along this axis such that its edge lo¬ cated most proximal the main channel 3 is tangential to the outer circumferential surface of the main channel. That portion of the main channel 3 located downstream of the opening 10 should also be of a length which amounts at least to fr¬ om 5 to 8 times the inner diameter of the main channel, in order that no disturbance thereby occur in the flow pattern in the main channel. in one practical optimation of a first embodiment of the sub¬ ject matter of the present invention, it has been noted that, in an positive pressure ofapproximately 1 kp/cm 2 of the compressor 1, the cross-sectional area of the throat in the nozzle 11 should amount to approximately 4% of the cross-sectional area of the main chan- nel, which, for example, may be realised in a throat diameter of 16 mm and an inner diameter of the main channel 3 of 76 mm. Further¬ more, in this embodiment, the angle between the two centre lines 13 and 14 should be, as has been mentioned above, 22°. In this embodi¬ ment, the inner diameter of the side channel 2 is 6 mm, or approxi- irately 72% of the inner diameter of the main channel 3. Further¬ more, the transport conduit 5 is of a diameter which exceeds the diameter of the main channel 3 by approximately 25 to 30%. In this embodiment, the material thickness of the main channel is approximately 2 mm, for which reason the most proximal edge of che nozzle opening 12 will lie 2 mm radially outside the inner cross-section of the main channel. The distance along the centre line 13 of the side channel 2 between the plane of the nozzle op¬ ening 12 and the point of disection between the two centre lines 13 and 14 of both channels is, in this embodiment, 128 mm. The corres- ponding distance along the centre line 14 of the main channel 3 is 120 mm and the distance parallel with the same centre line between the downstream edge of the opening 10 and the point of disection between the two centre lines 13 and 14 is 24 mm. DESCRIPTION OF ALTERNATIVE EMBODIMENT In a second embodiment of the present invention, the main channel has an inner diameter of 28 mm, while the throat diameter of the nozzle varies depending upon infeed pressure and desired transport capacity. In one case, it may amount to 3.4 mm. In this embodiment, the throat diameter of the nozzle is proportionally less than is the case in the above-described embodiment. In return, this embodiment operates at a higher pressure, namely in the order of magnitude of from 6 to 7 kg/cm 2 . in the above description, the subject matter of the present invention has been presented as being particularly designed for the transport of film strips, but the skilled reader will readily per¬ ceive that the present invention could just as well be employed for the transport of other types of materials, only the intake device 7 needing, in such an event, to be modified correspondingly. The invention should not be considered as restricted to that described above and shown on the Drawings, many modifications being conceivable without departing from the spirit and scope of the ap¬ pended claims.

Claims: CLAIMS 1. A conveyor apparatus, primarily intended for the transport of light plastic material such as film strips (9) or the like, and designed as an ejector, with one main channel (3) in which dis- charge means (2, 11) for the aspiration of a gas under pres¬ sure, characterised in that the main channel (3) has a straight and substantially cylindrical portion which is interiorly smooth- ; that said means for aspiration of the gas comprise a nozzle (11) which is located at an opening (10) in the wall of the main channel and radially outside the main channel, a centre line (13) through the nozzle making an acute angle with a centre line (14) of the main channel. 2. The conveyor apparatus according to claim 1, characterised in that the nozzle (11) is disposed in a side channel (2) whose connection to the main channel (3) covers the opening (10) there¬ of; and that the nozzle is directed and placed such that a point of disection between the centre line (13) of the nozzle and the centre line (14) of the main channel will be located downstream of the op¬ ening. 3. The conveyor apparatus according to claim 2, characterised in that the side channel (2) accommodating the nozzle is sub¬ stantially straight and cylindrical, the nozzle being coaxial ther¬ ewith. 4. The conveyor apparatus according to any one of claims 1 to 3, characterised in that the main channel (3) has, on its upstream side, an inlet channel (6) of substantially the same diameter as the main channel; and that the main channel has, at a distance downstream of the opening (10), a broadened portion (4). 5. The conveyor apparatus according to claim 4, characterised in that there is disposed, in the inlet channel (6), preferably at its intake (7), a throttle. 6. The conveyor apparatus according to any one of the pre¬ ceding claims, characterised in that the throat cross-sectional ar¬ ea of the nozzle (11) is approximately 4% of the cross-sectional area of the main channel (3); and that the angle between the centre line (13) of the nozzle and the centre line (14) of the main chan¬ nel lies in the region of between 20 and 25°. 7. The conveyor apparatus according to any one of claims 4 to 6, characterised in that the length of the main channel (3) between the broadened portion (4) and the nozzle (11) lies in the order of magnitude of from 5 to 8 times its diameter.

Inventors: HOLGERSSON LENNART, HOLGERSSON, LENNART
Applicants: RAPID AB MASKIN, MASKIN AB RAPID
Application year: 1985
Main classification: B65G53
IPC codes: B65G51