A unit for conveying containers

Technical Field The present invention relates to a unit for conveying containers. In particular, the invention relates to a unit for conveying bottles and similar receptacles, taken up at the outfeed stage of a dispensing and storage unit and fed in an ordered succession to the infeed stage of a user machine which, for example, could be a filling or capping machine.

Background Art The prior art embraces the use of conveyor units comprising a transport belt, on which containers are supported and caused to advance, delimited laterally by two restraints serving to guide the containers along what is generally a rectilinear feed path. Such units are fully able to perform the task required of them with no difficulty of any kind as long as the containers being handled, or at least the surfaces by way of which the containers make contact one with another, are of regular shape generated by a substantially constant cross section, for example cylindrical or parallelepiped. Drawbacks have been encountered in cases where the containers being handled present a substantially flared shape. In this instance the containers are significantly less stable, so that if subjected to impact or pressure from adjacent containers in the course of their passage along the aforementioned feed path, they will tend to tilt and become unstable to the point of toppling over. Attempts to overcome this problem include the adoption of conveyor belts furnished with pockets designed to accommodate the bases of the containers, thus guaranteeing their stability and keeping them in position. Such conveyor belts present the drawback, however, that the stations upstream and downstream of the belt must be equipped with devices by which the containers can be placed in and removed from the relative pockets, and this tends to complicate their structure and functionality. The object of the present invention is to provide a conveyor unit free of the drawbacks mentioned above.

Disclosure of the Invention The stated object is realized, according to the present invention, in a unit for conveying containers of which the features are recited in claim 1. The invention will now be described in detail, by way of example, with the aid of the accompanying drawings, in which: -figure 1 is the schematic illustration of a unit for conveying containers according to the invention, viewed in plan and partly as a block diagram; -figures 2, 3 and 4 show three types of containers by way of example, illustrated schematically and in perspective, for which the unit of figure 1 provides a particularly suitable transfer system; -figure 5 is a detail of figure 1, illustrated schematically and in perspective; -figure 6 is the section on V-V in figure 5; -figure 7 shows a portion of the unit in figure 1, viewed schematically and in perspective. -figure 8 is a detail of the unit in figure 1 shown in an alternative embodiment, viewed schematically and in perspective. Referring to figure 1, numeral 1 denotes a unit, in its entirety, by which containers 2 are conveyed in a direction denoted Fl. The conveyors 2 can present a flared shape, referable to a longitudinal axis 2a, for example elongated and flat as in the example of figure 2 illustrating a container 2 of which the flare is presented by divergent flank faces 2b disposed transversely to the feed direction Fl. The conveying unit 1 provides the link between a dispensing unit, represented schematically by the block denoted 3, and a user machine 4 of which the drawings show an infeed conveyor 5. The conveying unit 1 comprises conveyor means, denoted 6 in their entirety, serving to support and transfer the containers 2. In the example of figure 1 such means 6 are composed of a first conveyor belt 7 looped around respective return pulleys 8 and 9, positioned downstream along the feed direction Fl followed by the containers 2, and a second conveyor belt 10 looped around respective return pulleys 11 and 12, positioned upstream; the downstream pulleys 9 and 12 of the two belts are power driven by drive means denoted 9a and 12a respectively. The top branch 13 of the second conveyor belt 10 and the top branch 14 of the first conveyor belt 7, which extend in tandem and in a common plane between the outfeed stage 15 of the dispensing unit 3 and the infeed stage 16 of the infeed conveyor 5, combine to create the surface on which containers 2 emerging in succession from the dispensing unit 3 are carried. The advancing containers 2 are guided by means denoted 17 in their entirety, extending along the conveyor means 6 and establishing a predetermined feed path P of which a first leg Pa follows a substantially rectilinear course and a second leg Pb follows a substantially undulating course. With reference to figures 5 and 7, the first leg Pa of the guide means 17 presents a first and a second pair of lateral restraints denoted 18a and 19a respectively, positioned one above the other. The distance separating the two restraints of the upper pair 18a is greater than the distance separating the two restraints of the lower pair 19a. Similarly, the second leg Pb of the guide means 17 presents first and second pairs of lateral restraints denoted 20a and 21a respectively, positioned one above the other. The distance separating the two restraints of the upper pair 20a is greater than the distance separating the two restraints of the lower pair 21a. Thus, the aforementioned guide means 17 establish a relative guide channel 22 of which the transverse dimensions, determined by the successive pairs of restraints 18a-19a and 20a-21a, are marginally greater than the corresponding dimensions of the flared containers 2 standing on the top branch 13 of the second conveyor belt 10 and the top branch 14 of the first conveyor belt 7. More exactly, the restraints 18a and 19a delimiting the first leg Pa of the path P are afforded by the mutually opposed rectilinear edges of respective fences denoted 18 and 19, and the restraints 20a and 21a delimiting the second leg Pb of the path P are afforded by the mutually opposed undulating edges of respective fences denoted 20 and 21. As illustrated in figures 5, 7 and 8, the unit 1 further comprises auxiliary feed means denoted 23 placed along the undulated leg Pb of the feed path P, above the pair of fences 20 positioned uppermost. In particular, as discernible from figures 1 and 5, such auxiliary feed means 23 consist in pneumatic pushing means 24, connected in familiar fashion to a source of compressed air (not illustrated) and consisting in nozzles 25 positioned along the second leg Pb of the feed path P, distributed alternately at a selected pitch on either side of the channel 22 and in such a way as •to direct flat jets of pressurized air along the feed direction followed by the top branch 14 of the conveyor belt 7. In the example of figure 8, the auxiliary feed means 23 are provided by the bottom branch 26 of a push belt 27 looped around return pulleys 28 of which one only is visible and power driven, and positioned directly above the undulating channel 22 delimited by the relative fences 20 and 21. The push belt 27 is faced externally with a layer of pliant and/or resilient material 29, which in the example illustrated is shown as a continuous layer 30 of bristles, but might consist equally well in a continuous layer of foam rubber or similar material. With reference to figure 1, numeral 31 denotes means, in their entirety, by which the operation of the conveying unit 1 is monitored and controlled, comprising a first sensor 32 and a second sensor 33 placed along the undulated leg Pb of the feed path P and able to detect the presence of the containers 2. The first sensor 32 is placed at a predetermined distance from the outfeed end of the undulated leg Pb of the path P, and the second sensor 33 is placed upstream of the first, at the infeed end of the selfsame leg Pb. The sensors 32 and 33 are connected on the output side to a master control unit 34, which is connected in turn to the aforementioned drive means 9a and 12a. In operation, containers 2 dispensed by the upstream unit 3 are directed onto the top branch 13 of the second conveyor belt 10, along the rectilinear leg Pa of the feed path P, and forward to the top branch 14 of the first conveyor belt 7, passing along the undulated leg Pb of the feed path P internally of the channel 22. The containers 2 pass, as already indicated, from the conveyor means 6 to the infeed conveyor 5 of the user machine 4, which in the example of figure 1 consists in a screw feeder 35 affording pockets 36 and rotating about a horizontal axis 35a parallel to the feed direction Fl. To the end of avoiding breaks in the stream of containers 2 supplied to the infeed conveyor 5 and/or compensating differences in output at the dispensing unit 3 and the user machine 4, a reserve supply of containers 2 is created at least along a final part of the second leg Pb of the feed path P, extending from the infeed stage 16 of the screw feeder 35 back to a point between a minimum distance, determined by the first sensor 32, and a maximum distance 33 determined by the second sensor 33. The reserve of containers 2 is created by operating the conveyor means 6 at a feed velocity Vl greater than the feed velocity V2 of the infeed conveyor 5 serving the user machine 4. As a result of the different feed rates generated in this way, the capacity of the reserve supply can increase gradually until the line of containers 2 reaches back to the position of the second sensor 33 which, on detecting the continuous presence of a container 2, will send a signal Sl to the master control unit 34, which in turn generates a signal S2 to shut off the upstream drive means 12a, thereby- suspending the flow of containers 2 from the dispensing unit 3. During this step, with the second conveyor unit 10 in the pause state, the supply of containers 2 to the infeed 16 of the screw feeder 35 will be guaranteed by the first conveyor belt 7. At the moment the line of containers in the undulating channel 22 clears the first sensor 32, this will send a signal S3 to the master control unit 34 which in its turn generates a signal S2 to restart the drive means 12a, restoring the supply of containers 2 from upstream and allowing them to collect along the second leg Pb of the feed path P. The master control unit 34 will also control the operation of the downstream drive means 9a in such a way that the one velocity Vl always remains greater than the other velocity V2 in any situation. In practice, the containers 2 tend to bunch along the undulated leg Pb of the feed path P, and in particular along the reserve portion, but without their balance being adversely affected, thanks to the transverse displacements imposed on the selfsame containers 2 by the restraints 20a and 21a and to the fact that the containers 2 are able to lean against the selfsame restraints 20a and 21a. Also, the characteristics (length and width) of the undulations presented by the second leg Pb of the feed path P are selected according to the dimensions of the containers 2 as measured parallel to the feed direction Fl, so as to obtain optimum conditions in terms of flow and balance. Finally, it will be appreciated that the unit 1 is equally suitable for handling containers of the type illustrated in figure 3, presenting a flared shape of frustoconical appearance, or of the type illustrated in figure 4 presenting a flared shape of elliptical section, or containers of which the flared profile is attributable to the presence of a handle. Clearly, containers occupying the flow-compensating portion of the second leg Pb are subject to sliding contact both with the conveyor belt 7 and with the restraints 20a and 21a, and accordingly, both the conveyor belt 7 and the restraints 20a and 21a will be fashioned from materials having a low coefficient of friction, such as Teflon and the like. In addition, the movement of the containers 2 along the undulating channel 22 is favoured, and their balance maintained, by the action of the auxiliary feed means 23.