EP1127023A1

EP1127023A1 - Air-conveying apparatus with automatically adjusted transporting air stream

Info

Publication number: EP1127023A1
Application number: EP99950803A
Authority: EP
Inventors: Didier Charolle; Jo[L Trenel
Original assignee: Netra Systems SA
Current assignee: Netra Systems SA
Priority date: 1998-10-23
Filing date: 1999-10-20
Publication date: 2001-08-29
Also published as: FR2784975B1; AU6344699A; WO2000024654A1; CA2341592A1; FR2784975A1

Abstract

The invention concerns an air-conveying apparatus comprising, for each conveying section: means for measuring (10) the pressure inside the pneumatic conveyor(s) (5) or outside said pneumatic conveyor(s) (5), in the proximity of transporting air jets, said measuring means (10) delivering one or several control signals (10a); and means for automatically adjusting (11, 13) the measured value, on the basis of one or several predetermined set values and of the control signal(s) delivered by the measuring means, said measuring means being designed to act on the air flow rate input into the pneumatic conveyor(s) (5) of the section.

Description

AIR CONVEYOR WITH AUTOMATICALLY REGULATED AIRFLOW

The present invention relates to the field of pneumatic transport of articles, under the action of air jets. Its purpose is an air conveyor, the air flow for transporting the articles is automatically regulated. The invention finds more particularly, but not exclusively, its application to the pneumatic conveying of light articles, of the plastic container type (PET, PVC.) Which are suspended during their transport on a guide rail, and which are transferred along this guide rail under the action of air jets.

It has been known for many years to transport light articles, by means of air conveyors using a plurality of transport air jets directed on the articles so as to cause them to advance in a given transport direction. In general, these air conveyors are formed by one or more successive aeraulic sections, each aeraulic section comprising one or more successive blowing boxes which are designed to be supplied with pressurized air by at least one fan. Each blowing box has a plurality of slots and / or blowing orifices, which are judiciously distributed along the path of the articles, and which allow an escape of pressurized air in the form of a plurality of air jets which are directed on the articles.

In a first known type of air conveyor, the articles are transported by being suspended and guided on a guide rail. This type of conveyor is particularly well suited to the online transfer of plastic containers provided with a collar forming a protuberance, and in particular of plastic bottles or preforms (PET, PVC, etc.).

Patent US-A-4,284,37O describes an example of this first type of air conveyor in which the blowing slots of the blowing boxes are arranged above the guide rail of the articles which makes it possible to propel the articles by blowing above their collar. The patent US-A-5, 1 61, 91 9 describes another example of this first type of air conveyor in which the blowing slots of the blowing boxes are arranged below the guide rail, which makes it possible to propel articles by blowing under their collar. It is also possible to design air conveyors combining both transport air jets generated at or above the article guide rail, and transport jets generated below the article guide rail .

In a second known type of air conveyor, the articles are not suspended, but are transported on the surface of a transport apron. This apron may be constituted by the upper wall of the blowing boxes, which wall is in this case provided with slots and / or blowing orifices for the creation of transport air jets. Also, lateral transport air jets directed on the articles and created above the transport apron can be implemented. This type of air conveyor is for example used for the transport of articles not having a flange for their suspension, and for example cans, various packages, etc.

In practice, when the aforementioned air conveyors are installed on an industrial site, it frequently happens that they are subjected to significant temperature variations during the course of a day. In particular, in certain geographical areas, the differences in day and night temperatures can be very significant. Also during the day there are significant temperature differences between the morning and the evening. These temperature differences are further accentuated when air conveyors are installed high in poorly insulated and air-conditioned industrial premises. In practice, we see that the surrounding temperature of an air conveyor reaches in many cases 40 ° C, and can in certain cases exceed this value and reach up to 60 ^° C during the day, and that this temperature can conversely drop to around 20 ° C. These large temperature differences disturb the proper conveying of the articles. In particular, when the temperature increases too much, there is a noticeable loss of speed of the articles transported, leading to a degradation of the efficiency of the conveyor, which can go in certain cases up to a stop of the conveyor.

To date, it has been considered that this deterioration in the conveyability of the articles under the effect of large variations in temperature is mainly due to a significant variation, under the effect of temperature, of the coefficients of friction between the articles and their support (guide rail or transport apron). In particular, in the case of a plastic article, it has hitherto been considered that high temperatures contribute to making plastic articles "sticky", and thereby significantly increase the frictional forces between the articles. and their support. Knowing that it is not possible to modify the structure of the articles transported to make them insensitive to temperature differences, no satisfactory technical solution has been proposed to date to overcome this technical problem. The only solution possibly envisaged would be to act on the cause of the deterioration of the conveyability of the conveyors, that is to say to maintain the ambient temperature of the air conveyors at a substantially constant level, for example by air conditioning the industrial premises. in which the air conveyor is installed. However, this solution is on the one hand extremely expensive, and on the other hand is not really conceivable in practice when the air conveyors are installed in height at more than two meters from the ground.

The invention aims to provide an air conveyor, which unlike air conveyors known to date, is not or almost not affected by the temperature variations of its surrounding air.

The solution of the invention is based on the implementation of a automatic regulation of the transport air flow of the articles, in order to maintain at a substantially constant level the flow of transport air, which makes it possible to obtain a conveyor which adapts automatically and in real time to the temperature conditions of its surrounding air. The invention therefore relates to an air conveyor which in known manner comprises one or more successive conveying sections, each conveying section comprising one or more blowing boxes which are designed to be supplied with air under pressure, and which comprise a plurality of air exhaust ports for the creation of transport air jets directed on the articles so as to advance them.

Typically according to the invention, the air conveyor comprises, for each conveying section:

means for measuring the pressure inside the casing or blowing boxes, or means for measuring the speed or the air flow rate inside the blowing box or boxes or outside the or blowing boxes, in the vicinity of the transport air jets, which measuring means deliver one or more control signals,

- And automatic regulation means of the measured quantity, according to one or more predetermined set points and the control signal (s) delivered by the measuring means, which regulation means are designed to act on the incoming air flow in the blowing box or boxes of the conveying section.

It is the merit of the invention to have firstly demonstrated that the predominant factor affecting the conveyability of the articles under the influence of temperature differences was not mainly the modification of the coefficient of friction between the articles and their support, but was mainly linked to a significant change in the density of the air inside the blowing boxes in the event of a change in temperature. It was certainly possible, by reasoning a posteriori to consider that the temperature differences influenced the density of the air inside the blowing box and therefore on the speed or flow of air entering this blowing box. However, to the knowledge of the plaintiff, it has never before been demonstrated a priori that this influence of the temperature modifies the air flow in the blowing boxes in sufficiently large proportions to very strongly degrade the conveyability of the articles, and that it was enough to automatically regulate the flow of transport air in the blowing boxes, by acting on the air flow entering the blowing boxes, to compensate for the effects of temperature on the conveying articles. It should also be emphasized that the choice of the regulated quantity is also paramount for obtaining the result. Indeed, the first solution originally envisaged by the applicant was to automatically regulate the air flow entering the blowing box from a measurement of the temperature of the air surrounding the conveyor. However, after tests were carried out, this solution did not give satisfactory results.

Other characteristics and advantages of the invention will appear more clearly in the light of the description which will now be made of a preferred embodiment of an air conveyor according to the invention, which description is given by way of illustration. non-limiting example and with reference to the attached drawing in which:

- Figure 1 is a schematic sectional view of an example of an air conveyor, of known structure to which the invention can be applied, - and Figure 2 schematically illustrates the measuring means and the regulation means according to to the invention.

FIG. 1 shows an example of a known air conveyor, to which the invention can be applied. In the example illustrated, this air conveyor is used to transport, by pneumatic means, plastic bottles 1, in line one behind the other. Each bottle 1 usually comprises a protrusion 1 a forming flange, and is usually transported by being suspended and guided on a guide rail 2 formed by two sub-neck guides 3,4. Usually, the air conveyor comprises a plurality of successive conveying sections, each section being composed of one or more successive blowing boxes 5. The blowing boxes 5 of the same conveying section are supplied with pressurized air by means of the same fan 6, connected to one of the boxes of the section. The successive conveying sections forming the conveyor are, as a general rule and preferably, independent or almost independent from each other from an aeraulic point of view; for this purpose, the last blowing box 5 of a conveying section and the first blowing box 5 of the following section are separated by a sheet, at their internal volumes 5a pressurized and more commonly called "plenum". In FIG. 1, the bottom wall of each blowing box

5 forms in the middle part a recess 7 delimiting a blowing channel 8, which in the example illustrated has a rectangular section. At the step 7 delimiting the blowing channel 8, the blowing box 5 is provided with a plurality of air exhaust orifices 9 which in the example illustrated are in the form of blowing slots. In practice, the blowing slots 9 are judiciously distributed over the entire length of the blowing channel 8. The pressurized air discharged by the fan 6 inside the blowing box 5 escapes into the blowing channel 8, by the blowing slots 9, in the form of transport air jets which are oriented in the direction of the bottles 1, and which make it possible to propel the bottles 1 along the guide rail 2 formed by the under-neck guides 3, 4.

The invention, a preferred embodiment of which will now be described, is not limited to the particular structure of the air conveyor of FIG. 1 but is generally applicable to any air conveyor, in which the articles are transported by means of air jets of transport from blowing boxes supplied with pressurized air. In particular, the articles are not necessarily transported while hanging as in the conveyor of FIG. 1, but can be transported by air jets on the surface of a transport apron. Also, in other variants of air conveyors which are known to date and in which the articles are transported while hanging, the blowing slots can also be provided below the level of the under-neck guides 3; 4; the transport air jets can also come from channels which are produced in the guides under the neck 3.4, and which communicate with the interior of the blowing box 5. The air conveyor can also include secondary blowing boxes which are used for the creation of transport jets at the level of the body of the bottles.

FIG. 2 shows a particular example of implementation of the measurement and regulation means of the invention. In this FIG. 2, only one conveyor section of the conveyor has been shown diagrammatically, as well as the fan 6 supplying this section. In the particular example illustrated in FIG. 2, this section consists of a single blowing box 5. With reference to FIG. 2, in a preferred embodiment, the air conveyor of the invention implements, for each conveying section, a flow meter 1 0, making it possible to measure the flow rate of the air flow inside the blowing box of this section. This flowmeter, which in the illustrated example is located upstream of the fan 6, delivers a control signal 10a characteristic of the instantaneous air flow measured. This control signal 1 Oa is operated by automatic regulation means, which in the example illustrated are designed to act on the speed of rotation of the motor M of the fan 6, so as to maintain the flow of air discharged by the fan. inside the blowing box 5 at a substantially constant value fixed by a predetermined set point. More particularly, in the example illustrated, these regulation means use a regulator 1 1 and frequency converters 1 3 for adjusting the speed of rotation of the motors M of each fan 6. The regulator 1 1 receives as input the control signals 1 0a delivered by the flowmeters associated with each section of the conveyor, as well as the set values for each section (signal 12a) which are delivered by a programmable controller 1 2. At the output, the regulator 1 1 delivers signals 1 1 a for the frequency inverters 1 3 which respectively drive the motors M of the fans 6.

The set value set by each signal 1 2a delivered by the programmable controller 1 2 can be variable from one section of the conveyor to another and depends on the phase of transport of the bottles in this section (phase of transport in accumulation of bottles, transfer phase, docking phase ...). In practice, the set value is determined automatically and in real time by the programmable controller 12, from information delivered by two cells C1 and C2 which are associated with each section of the conveyor, and which makes it possible to detect the presence of bottles in the stretch. These cells C1 and C2 are, for example, optoelectronic or ultrasonic type cells.

The function of the regulator 1 1 in FIG. 2 is generally, for each conveyor section, to control the frequency converter 1 3 associated with the fan 6 of this section, so as to maintain the air flow measured by the flow meter 1 0 substantially at the set value delivered by the programmable controller 1 2. It may for example be a PI type regulation (Proportional / Integral) or a regulation by return of states, which in this case requires the modeling of a transfer function. In the particular example illustrated, the regulator 1 1 is dissociated from the programmable controller 1 2, and can be achieved by means of a card specific electronics. In another variant, this regulation could be integrated into the operating program of the programmable controller 1 2. Also, the programmable controller 1 2 can generally be replaced by any suitable processing unit.

The air conveyor which has just been described with reference to FIG. 2 has the main advantage of being able to adapt automatically to the temperature conditions of the air surrounding each section of the air conveyor and to reduce or even eliminate the risks of degradation of the conveyability and blockage of the bottles, linked to significant variations in the temperature of the air surrounding the conveyor. In particular, when the temperature of the air surrounding the conveyor increases, the density of the air inside the blowing boxes 5 decreases, and in the absence of regulation, the air flow rate measured by each flow meter 10 drops to a value which can be variable from one conveyor section to another. Thanks to the invention, this reduction in flow rate is automatically compensated for by the regulator 11, by an automatic increase in the speed of rotation of the motor M of each fan 6, so as to maintain a substantially constant air flow rate at the interior of each section.

Another advantage of the invention linked to the implementation of a flow measurement is the automatic compensation for the drop in air flow in the blowing boxes 5, linked to the fouling of the blowing slots 9 of the conveyor . In fact, during use, the blowing slots 9 of the conveyor may see their cross-sections for the passage of air jets decrease, due to their fouling. This phenomenon is frequently encountered, for example, on the conveyor sections located near a machine for filling bottles with a sweet liquid, the sugar particles tending to clog the blowing slots. In the event of fouling, the measured air flow tends to drop and this drop in flow is automatically compensated by the regulator 1 1, in the same way as for the temperature variations of the air surrounding the conveyor. Also, the fouling in time of the blowing slots 9 causes a variation in time of the value of the adjustment signal 1 1 a, delivered by the regulator 1 1 to each frequency converter. It thus advantageously becomes possible to provide an alert threshold at the level of the regulator on the level of this adjustment signal, which alert threshold corresponds to a maximum speed of the fan motor, which is characteristic of significant fouling of the slots. blowing, requiring an operation of cleaning the blowing channel 8 and the blowing slots 9.

The invention is not limited to the preferred variant embodiment which has just been described with reference to FIG. 2. In particular, it is possible within the framework of the invention to use several flow meters per conveying section. . Also, the measurement means used are not limited to the use of flow meters. It is for example conceivable to replace the flow measurement by an air speed measurement. Also the measurement of air flow or speed is preferably carried out in the blowing box, which avoids any risk of mechanical contact between the sensors used and the articles transported. However, it is also possible to carry out this measurement of air flow or speed outside the blowing box, near the transport air jets, that is to say in the particular example of FIG. 1 inside the blowing channel 8. With regard to the measuring means, it is also possible to replace the measurement of air flow or speed, by a measurement of the pressure inside the box. 5. The drawback, however, of this solution is that it does not make it possible to detect and compensate for the fouling of the blowing slots. Finally, in the particular example which has been described, the fans being at adjustable speed, the regulation means are preferably designed to act on the speed of rotation of the fans. This however is not limitative of the invention. In another variant, it would be possible to provide at the level of the discharge outlet of the fans, that is to say at the interface between each fan 6 and the corresponding blowing box 5, registers with adjustable opening, controllable electrically. In this case, the regulating means could be designed to automatically adjust the opening section of these registers so as to maintain the air flow entering the blowing box at a substantially constant level.

Claims

1. Air conveyor for transporting articles (1), of the type comprising one or more successive conveying sections, each conveying section comprising one or more blowing boxes (5) which are designed to be supplied with air under pressure, and which comprise a plurality of air exhaust orifices (9) for creating jets of transport air directed on the articles so as to cause them to advance, characterized in that it comprises, for each conveying section : - means for measuring (10) the pressure inside the blowing box or boxes (5), or means for measuring the speed or the air flow rate inside the blowing box or boxes (5) or outside the blowing box or boxes (5), in the vicinity of the transport air jets, which measuring means (10) deliver one or more control signals (10a), - and means automatic regulation (1 1, 13) of the measured quantity, depending on one or more several predetermined setpoints and one or more control signals delivered by the measuring means, which regulation means are designed to act on the air flow entering the blowing box or boxes (5) of the section.

2. Conveyor according to claim 1 characterized in that the means for supplying pressurized air to the blowing box or boxes (5) of a conveying section comprise at least one fan (6) with adjustable speed, and the means control (1 1, 13) are designed to automatically adjust the speed of rotation of each fan (6).