GB2286464A - Apparatus for metering a weighed quantity of tobacco - Google Patents

Abstract

An apparatus for metering a weighed quantity of tobacco comprises a container (18) for storing the tobacco to be metered; a coarse-dosing device (48) for providing a charge of tobacco having a weight approximating to that of the quantity to be metered; a fine-dosing device (52) for providing sufficient tobacco to make up the weight of the charge of tobacco provided by the coarse-dosing device (48) to that of the quantity to be metered; a conveyor (26) for transporting tobacco from said container (18) to said coarse and fine-dosing devices (48, 52); a weighing system (16) adapted to receive tobacco from both said coarse and fine-dosing devices (48, 52); and control means responsive to the weight of tobacco received by the weighing system (16) to control the quantities of tobacco provided by said coarse and fine-dosing devices (48, 52). The weighing system (16) comprises two or more weighing compartments and has means to direct the tobacco provided by said devices to a selected one of the compartments. <IMAGE>

Description

APPARATUS FOR DETERING A WEIGHED QUANTITY OF TOBACCO The present invention relates to an apparatus for metering a weighed quantity of tobacco.

In the past tobacco metering devices have been produced in which an appropriate quantity of tobacco is supplied to the weighing dish of a weighing machine from a storage container. The quantity of tobacco, which is supplied from the storage container by way of a first path, is regulated in accordance with the weight ascertained by the weighing machine. Thus, if the weight ascertained by the weighing machine corresponds to a desired value, the quantity of tobacco is removed from the weighing dish for further processing. Typically this is achieved by providing the weighing dish with a flap which, when opened, allows the quantity of tobacco to fall under the influence gravity into a conveyor.

If, on the other hand, the weight ascertained by the weighing machine is less than the desired value, the missing quantity is supplied to the weighing dish from the storage container by way of a second path. At the same time the quantity of tobacco which is supplied by the first path is increased so that during the next weighing operation the quantity supplied by the first path is closer to the desired value.

If the weight ascertained by the weighing machine is greater than the desired value, the quantity of tobacco is removed from the weighing dish in such a way that it can be returned to the storage container. At the same time the quantity of tobacco which is supplied by the first path is decreased so that during the next weighing operation the quantity supplied by the first path either corresponds to or is less than the desired value.

Clearly the over supply of tobacco to the weighing dish and its subsequent return to the storage container is wasteful of time and detracts from the overall efficiency of the tobacco metering device.

In an attempt to overcome these defficiencies improvements have been suggested to the coarse-dosing device which is responsible for supplying the quantity of tobacco by way of the first path and which responds to control signals from the weighing machine so that successive quantities are closer to the desired value. One such improvement is disclosed in UK Patent no. 1,589,979, the subject matter of which is incorporated herein by reference.In particular there is described in UK Patent no. 1,589,979 an apparatus for weighing out charges of tobacco, comprising a container for receiving the tobacco to be weighed out, a coarse-dosing device for providing a coarse-dosing weight of tobacco approximating to the desired weight, a feed pipe for supplying the coarse-dosing device with tobacco, a vibratory conveyor for feeding the tobacco from the container into the feed pipe, a fine-dosing device for providing a quantity of tobacco to make up the coarse-dosing weight precisely to the desired weight and a weighing machine having a weighing dish disposed in the region of the outlets of the coarse and fine-dosing devices, the coarsing-dosing device having at least one dosing compartment movable from a filling position to a discharge position and back, and means being provided for varying the coarse-dosing weight of the tobacco to be fed into the dosing compartment, wherein the dosing compartment is rotatably or slidingly mounted between two holding plates disposed one above the other, there being first and second boreholes in the upper holding plate, the feed pipe leads into the first borehole, first and second openings are provided in the lower holding plate at locations respectively opposite the first and second boreholes, the dosing compartment being in the filling position when it is aligned with the first borehole and the first opening, and being in a discharge position when it is aligned with the second borehole and the second opening, and there is a piston actuatable by a drive for accelerated ejection of the coarse-dosed tobacco into the weighing dish from the dosing compartment when the latter is in the discharge position.

Nevertheless despite this improvement, it has been found that the typical handling capacity of tobacco metering devices is limited whilst from time to time it is still necessary to return to the storage container a quantity of tobacco the weight of which exceeds the desired value.

Accordingly, the present invention seeks to address, at least in part, some of the disadvantages of the prior art.

According to the present invention there is provided an apparatus for metering a weighed quantity of tobacco comprising a container for storing the tobacco to be metered; a coarse-dosing device for providing a charge of tobacco having a weight approximating to that of the quantity to be metered; a fine-dosing device for providing sufficient tobacco to make up the weight of the charge of tobacco provided by the coarse-dosing device to that of the quantity to be metered; means for transporting tobacco from the container to the coarse and fine-dosing devices; a weighing system adapted to receive tobacco from both the coarse and fine-dosing devices; and control means responsive to the weight of tobacco received by the weighing system to control the quantities of tobacco provided by the coarse and fine-dosing devices, the weighing system comprising two or more weighing compartments and having means to direct the tobacco provided by the devices to a selected one of the compartments.

It has been found that the handling capacity of certain prior art tobacco metering devices is dependent on the capacity of the single weighing compartment with which it was equiped. Providing a second weighing compartment increases the capacity of the metering device so much that the metering device is capable of operating continuously. Clearly this results in a higher machine speed and an increased throughput. What is surprising however, is that the provision of a second weighing compartment also results in the metered quantities being of more accurate weight. As a consequence less tobacco is required to be supplied to the weighing compartment by the fine-dosing device which increases the capacity of the metering device still further.

Advantageously, the directing means may be interposed between the weighing compartments and the coarse and fine-dosing devices. Preferably the weighing compartments may be disposed side by side and the directing means comprise one or more inclined surfaces mounted on a shuttle, the shuttle being movable between successive positions in each of which tobacco falling on to one or more of the inclined surfaces slides off to be directed to a selective one of the weighing compartments.

Advantageously, the apparatus may comprise hopper means movable between a forwardly tilting position in which tobacco passing through the hopper means is directed to a respective one of the weighing compartments and a rearwardly tilting position in which the tobacco passing through the hopper means is directed to a recycling system adapted to return the tobacco to the container.

A number of embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic side view of a tobacco metering device emboding the present invention; Figure 2 is a schematic view from the other side of the metering device of Figure 1; Figure 3 is an enlarged cross-sectional view of one embodiment of a coarse-dosing device for use in the metering device of Figure 1; Figure 4 is an enlarged cross-sectional view of a second embodiment of a coarse-dosing device for use in the metering device of Figure 1; Figure 5 is a schematic view of one of the two paths by which tobacco is directed to a respective one of two weighing compartments; Figure 6 is a perspective view of a weighing system of the metering device of Figure 1; Figure 7 is a front view of the weighing system of Figure 6; and Figure 8 is a perspective view of the metering device of Figure 1 showing a conveyor used to transport a correctly metered quantity of tobacco to a subsequent workstation.

Referring to Figure 1, the tobacco metering device 10 can be seen to comprise three principle components: a tobacco storage container and feed system 12, a fine and coarse-dosing system 14 and a weighing system 16.

Looking at each of these components in turn, the tobacco storage container and feed system 12 comprises a storage container 18, a substantially horizontal endless conveyor belt 20 which is guided by guide-rollers 22 and 24, and an inclined endless conveyor belt 26 which is guided by guide rollers 28, 30, 32 and 34. The substantially horizonal conveyor belt 20 is disposed adjacent an under side of the storage container 18 so that tobacco from the storage container can fall onto the belt under the influence of gravity. Similarly, the inclined conveyor belt 26 is disposed adjacent and below one end of the substantially horizontal conveyor belt 20 so that on reaching guide-roller 22 tobacco moving along the horizontal conveyor belt falls onto the inclined conveyor belt and is carried upward towards guide roller 34.On its way the tobacco passes a scraper unit 36 which is disposed adjacent the inclined conveyor belt 26 and is shaped so as to level the tobacco and provide an even distribution along the belt. On reaching the guide roller 34, the tobacco falls, again under the influence of gravity, into the fine and coarse-dosing system 14 to be described below.

The substantially horizontal conveyor belt 20, which is preferably actuated by means of a free-wheel and an air cylinder, is controlled by means of a photocell 38 disposed within the storage container 18 so that the conveyor belt can only be actuated provided there is sufficient tobacco within the storage container to obstruct the photocell. By contrast, the inclined conveyor belt 26 is preferably driven by a dc motor (not shown) with the speed of both conveyor belts being controlled by means of potentiometer mounted within a control cabinet 40.

If the storage container 18 is itself filled automatically by an automatic tobacco feed (again, not shown), the storage container is preferably provided with one or more further photocells 42. In this way the automatic tobacco feed may be actuated when the or each further photocell 42 is no longer obstructed and switched off when sufficient tobacco has been delivered to the storage container 18 for the or each further photocell to be once more obstructed.

Turning now to a consideration of the fine and coarse-dosing system 14, the tobacco from the inclined conveyor belt 26 falls on to a vibrating trough 44. The vibrating trough 44 is provided with a false bottom in the form of a grating defined by a plurality of bars, the spaces between which can be varied depending on the characteristics of the tobacco to be metered. A distribution pipe 46 is disposed below the grating and extends substantially vertically downward so as to communicate with a coarse-dosing device 48. At the same time a second distribution pipe 50 also extends from a position just below the grating, albeit along an inclined path, to a fine-dosing device 52.The inclined distribution pipe 50 is provided at an end adjacent the grating with a flap 54 capable of closing the pipe whilst the vertical distribution pipe 46, which is preferably formed of plexiglass, is provided with two mutually spaced pairs of photocells 56 and 58. The purpose of the photocells 56 and 58 is to control the quantity of tobacco entering the vertical distribution pipe 46 having fallen through the grating. Thus, when the lower pair of photocells 56 is unobstructed a control signal is generated to actuate the horizontal and inclined conveyor belts 20 and 26 which are only stopped in response to a further control signal, this time generated by the upper pair of photocells 58, when sufficient tobacco has entered the vertical distribution pipe 46 so that the upper pair of photocells are once more obstructed.If for some reason the vertical distribution pipe 46 should become blocked this may be detected by a further sensor 60 disposed in alignment with the pipe at an end adjacent the vibrating trough 44 and used to generate a control signal to stop the metering device 10.

The coarse-dosing device 48 to which the tobacco is fed by the vertical distribution pipe 46 is similar to that disclosed in UK Patent no. 1,589,979. Refering to Figure 3, the coarse-dosing device 48 can be seen to comprise two horizontally extending holding plates 62 and 64 interposed between which there is provided a carriage 66 having a dosing compartment 68, both the carriage and dosing compartment being movable between a filling position and a discharge position. The lower of the two holding plates 62 is rigidly connected to a base plate 70 while the upper holding plate 64 is held by four bolts 72 of which only two are shown in Figure 3.Each of the bolts 72 pass through holding plate 64 at their upper end and it is at this end that each of the bolts is provided with a respective coil spring 74 which together urge the holding plate against the carriage 66.

The carriage 66 comprises a pipe section 76 which serves to define the dosing compartment 68. At respective opposite ends of this pipe section 76 the carriage 66 is provided with a pair of guide plates 78 which extended laterally of the pipe section and which, in at least one preferred embodiment, are slideably received in slots provided in the upper and lower holding plates 62 and 64.

The carriage 66 as represented by the solid lines is shown in Figure 3 in the filling position in which tobacco is directed to the dosing compartment 68 from the vertical distribution pipe 46 by way of a suitable aperture 80 provided in the upper holding plate 64. Directly below this aperture 80 there is provided a second aperture 82, this time in a lower holding plate 62. A low pressure pipe system 84 communicates with the second aperture 82 to draw tobacco into the pipe section 76, the second aperture being fitted with a sieve 86 to prevent tobacco from being prematurally discharged from the dosing compartment 68. The low pressure necessary to obtain the desired tobacco density is generated by means of a fan 87 and varied by means of an infiltrated-air adjusting disc 89.The resulting partial vacuum is indicated on pressure gauge 91 whilst a dust container 93 and dust filter 95 are interposed between the fan 87 and the dosing compartment 68.

Once the dosing compartment 68 has been filled with tobacco, the carriage 66 is displaced laterally by means of a pneumatic drive cylinder 88 to the discharge position which is represented by the dashed lines in Figure 3. In this position the pipe section 76 communicates with two further apertures, one 90 in the upper holding plate 64 and the other 92 in the lower holding plate 62. A piston 94, disposed adjacent the coarse-dosing device 48, is arranged so as to extend through it is the aperture 90 provided in the upper holding plate 64 when it is actuated by a second pneumatic drive cylinder 96. Thus, when the carriage 66 is in the discharge position, the piston 94 may be extended into the pipe section 76 causing the tobacco in the dosing compartment 68 to be ejected through the aperture 92 in the lower holding plate 62 whereupon the tobacco falls, under the influence of gravity, into the weighing system 16. Once the tobacco has been ejected from the dosing compartment, the piston 94 is retracted and the carriage 66 returned to the filling position where a fresh quantity of tobacco is drawn into the dosing compartment 68 by a combination of gravity and the low pressure pipe system 84.

The volume of the dosing compartment 68 is selected in such a way that the quantity of tobacco ejected through the aperture 92 is as close as possible to 95% of the desired weight of tobacco to be metered. To this end the coarse-dosing device 48 may be adapted so as to allow the volume of the dosing compartment 68 to be varied. Once such arrangement is shown in Figure 4 in which a like parts of the coarse-dosing device have been identified by the same reference numerals as used previously. As can be seen, the coarse-dosing device 48 is provided with a dosing plunger 98 which is capable of being introduced into the dosing compartment 68 through the aperture 82 provided in the lower holding plate 62 when the carriage 66 is in the filling position.The depth and penetration of the dosing plunger 98 into the dosing compartment 68 depends on the setting of a stop lever 100 against which there abutts a shoulder 102 of a piston rod 103 of a drive cylinder 104. The setting of stop lever 100, and thus the volume of the dosing compartment 68, is in turn determined by an eccentric disc 106, the rotational position of which may be altered by means of dc motor 108 in response to an appropriate control signal generated by the weighing system 16.

The operational sequence of the coarse-dosing device of Figure 4 is similar to that of Figure 3 except that when the carriage 66 is first returned to the filling position the drive cylinder 104 is actuated and the dosing plunger 98 introduced into the dosing compartment 68. Only then is a closing plate 110 removed from the aperture 80 provided in the upper holding plate 64 to allow tobacco to enter the dosing compartment 68 from the vertical distribution pipe 46. When the dosing compartment 68 has been filled with tobacco, the vertical distribution pipe 48 is once more closed by the closing plate 110 and the drive cylinder 104 actuated so as to withdraw the dosing plunger 98 until its upper face is flush with the lower holding plate 62.Once in this position the carriage 66 is free to be moved to the discharge position with the remainder of the operational sequence as previously discribed.

Further modifications to the coarse-dosing device 48 will be apparent to those skilled in the art not least from a reading of UK Patent no. 1,589,979 the subject matter of which, as stated previously, is incorporated herein by reference.

Whatever the design of the coarse-dosing device 48, the tobacco metering device 10 is preferably provided with a Dosoll lubricating device 112 capable of providing a continuously adjustable quantity of lubricating fluid, particularly if tne tobacco to be metered contains a lot of casing or is overly moist.

As mentioned above, the coarse-dosing device 48 is intended to provide the weighing system 16 with as close as possible to 95% of the desired weight of the tobacco to be metered. The remaining 5% is provided by the fine-dosing device 52.

In contrast to the coarse-dosing device 48, the fine-dosing device 52 comprises a spiral vibrator 114 disposed at an end of the inclined distribution pipe 50 remote from the flap 54. The spiral vibrator 114 is in turn comprised of a plate 116 defining a substantially helical path and a vibration unit 118 for vibrating the plate. Fine tobacco particles falling onto the spiral vibrator 114 are caused by the vibrations to travel along the helical path defined by the plate 116 until, on reaching an edge of the spiral vibrator, they also fall, again under the influence of gravity, into the weighing system 16. As soon as the desired weight of tobacco is registered by the weighing system 16 the vibration unit 118 is switched off thereby preventing further tobacco particles from reaching the edge of the spiral vibrator 114.

The quantity of tobacco falling onto the spiral vibrator 114 is monitored by means of a sensor 120 disposed adjacent the end of the inclined distribution pipe 50 remote from the flap 54. If the quantity of tobacco detected by the sensor 120 is below a predetermined threshold, a control signal is generated to open flap 54 thereby enabling a fresh quantity of tobacco to enter the inclined distribution pipe 50 and fall towards the spiral vibrator 114.

In a departure from previous tobacco metering devices, the weighing system 16 comprises two independent weighing compartments 120 and 122 disposed side-by-side. Accordingly, tobacco falling from the coarse and fine-dosing system 14 is directed to the appropriate weighing compartment following by one of two paths. As can be seen from Figure 5, each of the two paths is defined by respective first and second hoppers 124 and 126. In each case the first hopper 124 defines a substantially vertical channel for the passage of tobacco but is closed at a lower end by means of a flap 128 which is movable between an open and a closed position under the action of a pneumatic drive cylinder 130.By contrast, each of the second hoppers 126 define an open-ended channel but are pivotable under the action of a further pneumatic drive cylinder 132 between a forwardly tilting position in which tobacco passing through the hopper is delivered to a respective one of the two weighing compartments 120 or 122 and a rearwardly tilting position in which the tobacco is delivered to a recycling system 133 for return to the storage container 18.

In order to determine which of the two paths is to be taken by the tobacco falling from the coarse and fine-dosing system 14, and therefore to decide to which of the two weighing compartments 120 and 122 the tobacco is to be delivered, a distributing guide 134 is interposed between the two first hoppers 124 and the coarse and fine-dosing devices 48 and 52. As can be seen from Figures 6 and 7 the distributing guide 134 is provided with oppositely inclined guide surfaces 136 and 138 that meet at an upper apex 140.As can also be seen from these Figures, the distributing guide 134 is mounted on a shuttle 142 between two guide rails 144 and 146 and is movable under the action of yet a further pneumatic drive cylinder 148 between a first position, shown in Figure 6, in which tobacco falling from the coarse and fine-dosing system 14 impacts upon the distributing guide and slides down inclined guide surface 138 to be directed to the path leading to the right of the two weighing compartments 122 and a second position, not quite reached in Figure 7, in which the falling tobacco impacts upon the distributing guide and slides down inclined guide surface 136 to be directed to the path leading to the left of the two weighing compartments 120.

In use a quantity of tobacco is ejected from the dosing compartment 68 of the coarse-dosing device 48 and falls onto the distributing guide 134 to be directed to either the left or the right of the two first hoppers 124. There, with the flap 128 in the closed position, the quantity of tobacco is weighed. If the measured weight is equal to or less than that of the quantity to be metered, pneumatic drive cylinder 132 is actuated to pivot the associated second hopper 126 to the forwardly tilting position. Only then is pneumatic drive cylinder 130 actuated to move the flap 128 to the open position and allow the tobacco to fall from the first hopper 124, through the second hopper 126 and into the appropriate weighing compartment. There the tobacco is weighed again and if the measured weight is less than that of the quantity to be metered the vibration unit 116 of the fine-dosing device 52 is actuated so as to cause fine tobacco particles to fall from the edge of the spiral vibrator 114. With the flap 128 still in the open position and the second hopper 126 still in the forwardly tilting position the fine tobacco particles are allowed to reach the weighing compartment thereby increasing the weight of the tobacco contained therein. When this weight reaches that of the quantity of tobacco to be metered the vibration unit 116 is switched off and a flap 150 is opened in the floor of the weighing compartment to allow the tobacco to fall into a conveyor 152 disposed below the compartment.The conveyor 152 with the correctly metered quantity of tobacco is then transported to a subsequent workstation where the tobacco is processed further.

At the same time as the vibration unit 116 is switched off, pneumatic drive cylinder 148 is actuated to move the shuttle 142 to the other end of the guide rails 144 and 146 so that the distributing guide 134 may direct the next quantity of tobacco to be ejected from the coarse-dosing device 48 to the other of the two first hoppers 124 whereupon the weighing process is repeated.

Should at any time the measured weight of the tobacco within either of the first hoppers 124 exceed the quantity to be metered, the relevant pneumatic drive cylinder 132 is actuated to pivot the associated second hopper 126 to the rearwardly tilting position. Only then is pneumatic drive cylinder 130 actuated to move the flap 128 to the open position and allow the tobacco to fall from the first hopper 124, through the second hopper 126 and into the recycling system for return to the storage container 18.

By changing the direction of pivotal movement of the second hopper 126 from side to side to forward and back it has been possible to create sufficient space to provide two independently operable weighing compartments side by side.

This in turn has led to a dramatic increase in the speed at which the tobacco metering device 10 can operate. Whereas in prior art devices the next quantity of tabacco could not be ejected from the coarse-dosing device 48 until after sufficient fine tobacco had been added to the previous charge by the fine-dosing device 52 and the correctly metered quantity had begun its journey to the next workstation, now the two weighing compartments 120 and 122 can be operated in parallel enabling a fresh quantity of tobacco to be delivered to one of the compartments from the coarse-dosing device while the other compartment still contains the previous charge.

This increased operating speed somewhat surprisingly also results in the metered quantities being of more accurate weight. This is because each of the individual weighing compartments 120 and 122 actually has more time in which to determine the weight of the tobacco which is delivered to it. As a result the tobacco delivered by the coarse-dosing device 48 many be allowed to drain completely through the first and second hoppers 124 and 126 thereby requiring less additional tobacco to be added from the fine-dosing device 52.

It will be apparent to those skilled in the art that, if desired, a tobacco metering device may be provided with more than two weighing compartments. Likewise, it will also be apparent to those skilled in the art that whilst the means to direct the falling tobacco to a selected one of the weighing compartments has been described as an appropriately shaped shuttle interposed between the weighing compartments and the coarse and fine dosing devices, this need not necessarily be the case. Indeed one or both of either the weighing compartments or the coarse and fine dosing devices may be adapted to move so that at any one time the coarse and fine dosing compartment are disposed directly above a selected one of the weighing compartments. In such an arrangement there would be no requirement for a means to direct the falling tobacco to be interposed between the two.

Claims (5)

1. An apparatus for metering a weighed quantity of tobacco comprising a container for storing the tobacco to be metered; a coarse-dosing device for providing a charge of tobacco having a weight approximating to that of the quantity to be metered; a fine-dosing device for providing sufficient tobacco to make up the weight of the charge of tobacco provided by the coarse-dosing device to that of the quantity to be metered; means for transporting tobacco from said container to said coarse and fine-dosing devices; a weighing system adapted to receive tobacco from both said coarse and fine-dosing devices; and control means responsive to the weight of tobacco received by the weighing system to control the quantities of tobacco provided by said coarse and fine-dosing devices, the weighing system comprising two or more weighing compartments and having means to direct the tobacco provided by said devices to a selected one of said compartments.

2. An apparatus in accordance with claim 1, wherein said directing means is interposed between said weighing compartments and said coarse and fine-dosing devices.

3. An apparatus in accordance with claim 2, wherein said weighing compartments are disposed side-by-side and said directing means comprises one or more inclined surfaces mounted on a shuttle, the shuttle being movable between successive positions in each of which tobacco falling onto one or more of the inclined surfaces slides off to be directed to a selected one of the weighing compartments.

4. An apparatus in accordance with any preceding claim and comprising hopper means movable between a forwardly tilting position in which tobacco passing through the hopper means is directed to a respective one of the weighing compartments and a rearwardly tilting position in which the tobacco passing through the hopper means is directed to a recycling system adapted to return the tobacco to said container.

5. An apparatus for metering a weighed quantity of tobacco substantially as herein described with reference to the accompanying drawings.