Apparatus For Transporting Cigarette Packs In Packing Machines

Abstract

Apparatus for transporting cigarette packs to or from the cells of a rotary turret in a packing machine comprises a foraminous belt whose upper stretch transports the packs, a chamber adjacent to the underside of the upper stretch and having an open upper side which is overlapped by the belt, and a blower which circulates air through the chamber and the perforations of the belt, either in a direction to evacuate air from the chamber whereby the packs which travel with the upper stretch are drawn against the belt during travel along the open side of the chamber, or in a direction to expel air from the chamber and through the perforations of the belt so that such air forms a cushion which reduces friction between the upper stretch and the packs.

Description

BACKGROUND OF THE INVENTION

The present invention relates to improvements in apparatus for transporting cigarette packs or analogous block-shaped articles, particularly for transporting packs containing smoking products to and from packing machines wherein the packs are provided with envelopes of transparent, translucent or opaque sheet material.

It is already known to wrap packs containing cigarettes or other smoking products into sheets of transparent synthetic plastic material while the packs occupy cells in an intermittently or continuously revolving turret. The packing machine which embodies the turret is further provided with a feeding unit which delivers unwrapped packs to, and with a takeoff unit which receives wrapped packs from, the turret. The feeding and/or the takeoff device normally comprises an endless belt whose surface is roughened to reduce the likelihood of slippage of packs with reference to the belt during transport into or from the cells of the turret. Such solution is not entirely satisfactory because the roughened part of the belt can damage or deface the packs; furthermore, a roughened surface cannot prevent slippage of packs which must be transported at a very high speed to or from the turret of a modern packing machine.

It is also known to provide the feeding device or the takeoff device with a belt which cooperates with spring-biased presser rolls. These rolls serve to press the packs against the belt so that the packs cannot slide with reference to the belt or vice versa. A drawback of this proposal is that the presser rolls are likely to deform or to otherwise affect the appearance and/or condition of relatively soft packs, especially if the packs are to be transported at a very high speed and must be pressed against the belt with a considerable force.

SUMMARY OF THE INVENTION

An object of our invention is to provide an apparatus for transporting packs containing smoking products to and/or from a packing machine in such a way that the packs can be transported at a very high speed, without appreciable deformation and at desired intervals.

Another object of the invention is to provide a transporting apparatus which can be utilized as a substitute for the feeding or takeoff device of a conventional packing machine wherein packs containing cigarettes, cigars, cigarillos or other smoking products are provided with transparent, translucent and/or opaque envelopes.

A further object of the invention is to provide a transporting apparatus whose operation can be readily synchronized with operation of the machine which supplies thereto unwrapped packs or analogous articles or which receives such articles from the transporting apparatus.

An additional object of the invention is to provide the transporting apparatus with a novel monitoring device which can detect flaws in the rate of transport of articles and can initiate remedial action to correct the flaw or to insure stoppage of parts which cause or can be affected by improper transport of articles.

Still another object of the invention is to provide a transporting apparatus which comprises a small number of simple parts, which requires little or no attention when in use, and which can be adjusted to transport lighter, heavier, smaller, bulkier and/or differently configurated packs or analogous articles.

Our invention resides in the provision of an apparatus for transporting packs of cigarettes or other smoking products, particularly for delivering packs into or for removing packs from movable cells or analogous receptacles of a packing machine. The apparatus comprises a travelling foraminous conveyor, preferably an endless perforated belt having a receiving end, a discharge end, and an intermediate portion extending between the two ends and having an article supporting side and a second side, a chamber adjacent to the second side of the intermediate portion in the region of one of the ends and having an open portion which is overlapped by a part of the intermediate portion of the conveyor, and air circulating means operative to convey currents of air through the chamber and through the overlapping part of the intermediate conveyor portion to thereby influence friction between the conveyor and the packs. If the chamber is a suction chamber, i.e., if it is connected with a suction generating part of the air circulating means, suction created in the chamber causes the packs to adhere to the first side of the intermediate conveyor portion so that such packs are less likely to move with reference to the conveyor or vice versa. If the chamber is a plenum chamber, i.e., if it is connected to an air-compressing part of the air circulating means, currents of air issuing from the open side of the plenum chamber and passing through the perforations of the conveyor can form along the first side of the intermediate conveyor portion an air cushion which reduces or eliminates friction between the conveyor and the packs so that the conveyor can remain in motion while the packs are held against movement with the intermediate portion.

If the air circulating means comprises a suction generating part and an air compressing part, the apparatus can further comprise regulating means for connecting the chamber with one of the parts at a time so that the chamber is a suction chamber and causes an increase in friction between the packs and the intermediate conveyor part when it is connected with the suction generating part and that the chamber is a plenum chamber when it is connected to the air-compressing part to thereby reduce friction between the packs and the intermediate conveyor part.

The operation of the air circulating means can be programmed as a function of operation of the machine which receives packs from or delivers them to the conveyor of the transporting apparatus. If the chamber is adjacent to the discharge end of the conveyor and normally serves as a suction chamber, the apparatus can further comprise means for controlling the operation of the air circulating means as a function of the condition of the machine which receives packs from the discharge end. For example, the controlling means may include a valve which connects the chamber to the atmosphere or with an air-compressing part of the air circulating apparatus when the machine which receives packs from the conveyor is arrested so that friction between the conveyor and the packs then decreases to insure that the packs are not damaged if they are held against movement off the intermediate part while the conveyor remains in motion.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved transporting apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a partly elevational and partly central longitudinal vertical sectional view of a packing machine which comprises two transporting apparatus each of which is constructed and assembled in accordance with a first embodiment of our invention;

FIG. 2 is a top plan view of a part of the structure shown in FIG. 1;

FIG. 3 is a fragmentary longitudinal vertical sectional view of a packing machine which comprises a modified transporting apparatus; and

FIG. 4 is a partly sectional perspective view of a monitoring device for one of the transporting apparatus shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIGS. 1 and 2, there is shown a portion of a packing machine which is designed to provide cigarette packs 5 with envelopes of preferably transparent or translucent sheetlike synthetic plastic wrapping material. The packing machine comprises a rotary conveyor here shown as a turret 30 and two novel transporting conveyors one of which feeds cigarette packs 5 into successive receptacles or cells 47 of the rotary part of the turret 30 and the other of which receives wrapped packs 5a from such cells. The turret 30 comprises a stationary base plate or platform 31 which is mounted on a frame 32 and a rotor or wheel 33 which is provided with radially extending entraining members or blades 34. The wheel 33 is secured to a vertical drive shaft 35 and rotates on a thrust bearing 36 surrounding the shaft 35 in the region directly above the platform 31. The shaft 35 rotates in a radial antifriction bearing 37 which is mounted in the frame 32 and the lower end portion of this shaft is rigid with two coaxial gears 45, 46. The indexing means for intermittently rotating the main shaft 35 comprises an electric motor 38 which drives the input member of a variable-speed transmission 39. The output member 41 of the transmission 39 carries a gear 42 which is coplanar with and drives the gear 45 by way of an endless chain 43. The gears 45, 46 form integral parts of a gear cluster 44.

That transporting conveyor which delivers unwrapped cigarette packs 5 to the cells 47 of the wheel 33 comprises an endless foraminous belt 3 which is provided with a smooth external surface. That transporting conveyor which receives wrapped cigarette packs 5a from the cells 47 comprises a second endless foraminous belt 48. The perforations or openings of the belts 3 and 48 are respectively shown at 4 and 49. The left-hand end or receiving end of the belt 48 extends into a recess 31a of the platform 31. The discharge end of the belt 3 is trained over a roller 51 which is adjacent to the periphery of the platform 31 and the receiving end of this belt is trained over a second roller, not shown. The receiving end of the belt 48 is trained over a roller 52 which is adjacent to the innermost portion of the recess 31a. The discharge end of the belt 48 is trained over a second roller, not shown. The platform 31 is provided with an extension 53 which is immediately adjacent to the discharge end of the belt 3 and is provided with a lateral stop or rail 54 for cigarette packs 5.

The first transfer conveyor further comprises a suction chamber 55 installed below the underside of the upper stretch of the belt 3 and having an open upper portion so that it can draw currents of air across the openings 4 to thereby cause cigarette packs 5 to adhere to the exposed upper side of the belt 3 during transport toward the rotor 33. The upper stretch constitutes an intermediate portion which extends between the receiving and discharge ends of the belt 3 and a part of which overlaps the open top portion of the chamber 55. The chamber 55 is connected with a suction conduit 56 which is connected with a second suction conduit 58 by way of a regulating valve 57. The conduit 58 is connected with a vacuum tank 59 which is connected to the suction side of an air circulating device (e.g., a blower) 62 by a further suction conduit 61. A second suction chamber 63 is installed below the upper stretch of the belt 48 and has an open top portion which attracts wrapped cigarette packs 5a to the upper side of this belt during transport of packs 5a away from the wheel 33. The suction chamber 63 is connected with the vacuum tank 59 by way of suction conduits 64, 66 which contain a second regulating valve 65. The valve members of valves 57, 65 are biased by springs and can be actuated by the lobes 68 of a rotary programming cam 67 which is driven by the gear 46 of the cluster 44 by way of an endless chain 72 and a gear 71 mounted on the camshaft 69.

The platform 31 and its extension 53 are provided with ports or orifices 73 located above the open upper side of a pressure chamber or plenum chamber 74 connected with the pressure side of the blower 62 by way of conduits 75, 78 which contain a flow restrictor or throttle 76 and a pressure tank 77. A further flow restrictor or throttle 81 is installed in a discharge conduit 79 which communicates with the conduit 78. The conduit 79 discharges surplus air into the surrounding atmosphere. The ports 73 are provided in those portions of the platform 31 and extension 53 which are located below the path of movement of cigarette packs 5 into the cells 47 of the wheel 33. The means for driving the blower 62 comprises a separate electric motor (not shown) which is started and arrested with the motor 38, or the transmission 39 comprises a second output member which can drive the rotary part or parts of the blower 62. The wheel 33 is indexed intermittently and the drives (not shown) which move the belts 3 and 48 continuously are designed in such a way that the belts 3, 48 advance by a distance which at least equals the length of a pack 5 or 5a, as considered in the longitudinal direction of the upper stretches of these belts, during each interval between successive indexing movements of the wheel 33. The transmission ratio between the main shaft 35 and camshaft 69 is such that the regulating valves 57, 65 are opened by lobes 68 of the programming cam 67 during a predetermined portion of each interval between indexing movements of the wheel 33. Thus, the regulating valves 57, 65 insure that the suction chamber 55 communicates with the vacuum tank 59 by way of the suction conduits 56, 58 when the suction chamber 63 communicates with the vacuum tank 59 by way of the conduits 64, 66.

The operation

The transmission 39 drives the wheel 33 intermittently in such a way that the length of intervals between successive indexing movements is very short. When the wheel 33 comes to a halt upon completion of a step in a clockwise direction, as viewed in FIG. 2, the wheel 33 assumes a position corresponding to that shown in FIGS. 1 and 2. Two lobes 68 of the programming cam 67 then maintain the regulating valves 57, 65 in open positions so that the suction chambers 55, 63 are connected with the vacuum tank 59. These suction chambers draw air through the adjoining openings 4 and 49 and thus insure that the packs 5, 5a are attracted to the upper stretches of the respective belts 3, 48 so that each such pack is moved lengthwise at the exact speed of the corresponding belt. Thus, the wrapped pack 5a in that cell 47 which enters the transfer station 60 in the region above the recess 31a of the platform 31 is automatically and rapidly evacuated from its cell by the receiving end of the upper stretch of the belt 48. At the same time, the packs 5 which adhere to the upper stretch of the belt 3 due to suction in the chamber 55 form a pusher or ram which pushes the preceding pack 5 onto the extension 53 of the platform 31 and into the registering cell 47 of the wheel 33. The transfer station which accommodates the extension 53 is denoted by the numeral 50. The foremost pack 5 comes to a halt when its front end face abuts against the bottom surface or inner surface 33a in the registering cell 47. The purpose of the plenum chamber 74 is to discharge through orifices 73 a certain amount of air which forms a cushion at a level directly above the extension 53 and thus insures that the foremost pack 5 can enter the registering cell 47 with minimal friction. The rate at which the chamber 74 discharges compressed air through the orifices 73 can be regulated by appropriate adjustment of the throttle 76 in the pressure conduit 75.

The programming cam 67 permits the aforementioned springs to close the regulating valves 57, 65 at the exact moment when a fresh pack 5 reaches the bottom surface 33a in the registering cell 47. The suction chambers 55, 63 are then disconnected from the vacuum tank 59 and communicate with the atmosphere by way of regulating valves 57, 65. Thus, vacuum in the chambers 55, 63 is destroyed abruptly so that the upper stretch of the belt 3 can slide with reference to the packs 5 which rest thereon. At the same time, the transmission 39 indexes the wheel 33 by a step whereby the blade 34 which is adjacent to the transfer station 50 entrains the pack 5 in that cell 47 which received the pack from the extension 53, and such pack moves with the wheel 33 through an angle of predetermined magnitude to place a fresh (empty) cell 47 into registry with the transfer station 50. At the same time, the wheel 33 moves a freshly wrapped pack 5a into the transfer station 60 so that such pack 5a can be withdrawn as soon as the regulating valve 65 again establishes a connection between the suction chamber 63 and vacuum tank 59. This completes one stage of the cycle and the next stage begins as soon as the programming cam 67 causes two of its lobes 68 to open the regulating valves 57, 65.

The means for feeding prefabricated sheetlike blanks of transparent or translucent plastic material into the path of movement of packs 5 into the cells 47 and the means which thereupon converts such blanks into envelopes is known in the art and forms no part of the present invention. As a rule, each blank is automatically draped over the front, top and bottom sides of a pack 5 while the latter enters its cell 47, and the wheel 33 then advances the partially wrapped pack past a series of stationary and/or movable tucking, folding, heat-sealing and like devices which complete the conversion of blanks into envelopes.

FIG. 3 illustrates a portion of a second packing machine wherein all such parts which are clearly identical with or analogous to the corresponding parts of the packing machine of FIGS. 1 and 2 are denoted by similar reference numerals plus 100. This illustration shows only the first transporting conveyor, namely, that conveyor which includes the foraminous belt 103. In this packing machine, the wheel or rotor 133 of the turret 130 is driven continuously and the second transfer conveyor of FIGS. 1 and 2 is replaced by a customary mechanical ejector, e.g., a pusher or plunger (not shown) which expels wrapped packs from the cells of the wheel 133 in a manner well known from the art of conventional packing machines. Furthermore, the suction chamber 55 of FIG. 1 is replaced by a chamber 190 which also replaces the plenum chamber 74. A conduit 189 connects the chamber 190 with a regulating valve 182 which is connected with the vacuum tank 159 by a suction conduit 184 and with the pressure tank 177 by a conduit 183. The latter contains a flow restrictor or throttle 176. A further conduit 178 connects the pressure tank 177 with the pressure side of the blower 162; the suction side of this blower is connected with the vacuum tank 159 by a further suction conduit 161. The regulating valve 182 is operated by an electromagnet 185 which is connected with a source of electrical energy by conductors 186, 187. A master switch 188 is installed in these conductors and is closed by hand when the packing machine is started, or automatically in response to starting of the drive for the wheel 133. In the latter instance, the switch 185 preferably opens automatically when the wheel 133 comes to a halt.

The operation of the structure shown in FIG. 3 is as follows:

In normal operation of the packing machine, the chamber 190 is a suction chamber, i.e., energization of electromagnet 185 causes the valve 182 to seal the conduit 189 from the pressure tank 177 and to connect this conduit with the vacuum tank 159 so that the packs 105 are attracted to the smooth upper side of the upper stretch of the belt 103 to thus insure that this belt supplies packs into successive cells of the continuously rotating wheel 133. That pack 105 which enters a cell is immediately entrained by the corresponding blade 134 of the wheel 133 and is transported along the aforementioned tucking, folding, heat-sealing and like devices which convert the respective blank into an envelope before the pack reaches the mechanical ejector which expels the pack from the cell and causes it to move onto a conventional takeoff conveyor, not shown. The chamber 190 insures that the packs 105 cannot slide with reference to the upper stretch of the belt 103 and the latter is driven at such a speed that it invariably delivers a fresh pack 105 into an empty cell of the wheel 133 before the adjoining blade 134 reaches the transfer station 150. The electromagnet 185 is energized because the master switch 188 is closed as long as the wheel 133 rotates. When the wheel 133 comes to a halt, for example, because a pack jams at a point between the transfer station 150 and the other transfer station, the master switch 188 opens automatically to deenergize the electromagnet 185 whereby the latter permits a spring 182a to change the position of the valve member in the regulating valve 182 in such a way that the conduit 189 is sealed from the vacuum tank 159 but is connected with the pressure tank 177. The chamber 190 is then converted into a plenum chamber and discharges air through the openings 104 at such a rate (determined by setting of the adjustable throttle 176) that the air forms a cushion above the upper stretch of the belt 103. Thus, the drive for the belt 103 need not be arrested when the wheel 133 comes to a halt because the packs 105 then "float" on a cushion of air above the upper stretch of the belt 103 and do not exert a strong pressure against the bottom surface 133a of the wheel 133. The regulating valve 182 is reset automatically when the wheel 133 starts to rotate and the valve then connects the conduit 189 with the suction conduit 184 while simultaneously connecting the conduit 183 with the atmosphere.

The cushion of air which develops above the upper stretch of the belt 103 when the electromagnet 185 is deenergized insures that the upper stretch of the belt 103 cannot scratch or otherwise deface or damage the packs 105 while the foremost pack bears against the bottom surface 133a of the arrested wheel 133.

The transporting apparatus of our invention has been used with very satisfactory results in connection with high-speed machines wherein cigarette packs are provided with envelopes of transparent or translucent synthetic plastic material. It was found that the apparatus can transport packs to or from the turret of the packing machine at desired rates of speed without any deformation and/or other damage to the packs, even if the packs are transported at very high speeds. In presently known packing machines, the delivery of packs into and withdrawal of wrapped packs from the turret often presents serious problems which cannot be overcome by resorting to aforementioned conventional transporting apparatus. Suction in the chambers which are adjacent to the receiving or discharging end of the foraminous conveyor can be readily selected in such a way that the packs adhere to the upper stretch of the belt without any slippage so that the packs can be transported at an optimum speed, not only into but also away from the cells of the intermittently or continuously rotating turret.

An important requisite for satisfactory operation of packing machines for cigarette packs or the like is to insure that any flaws in the feed of fresh packs to the intermittently or continuously rotating wheel of the turret are detected without appreciable delay so that the operator or an automatic control system of the machine can undertake certain steps in order to avoid damage to the machine and/or to cigarette packs. Since the packing machine normally operates at a very high speed, even short delays in detection of unsatisfactory feed of packs to the cells of the wheel 33 or 133 could result in substantial losses in output. For example, interruptions or disturbances in the feed of cigarette packs 5 or 105 should immediately initiate stoppage in delivery of wrapping material, stoppage of delivery of paste which is often employed to seal the overlapping portions of envelopes, stoppage of the feed which delivers tax stamps, and or other functions. As a rule, the takeoff conveyor (namely, the conveyor which includes the belt 48 of FIGS. 1 and 2 or a conveyor which receives wrapped packs from the mechanical ejecting device mentioned in connection with FIG. 3) has a relatively small capacity so that it cannot receive a very large number of wrapped packs. If there is a disturbance in the operation of mechanism which receives or removes wrapped packs from the takeoff conveyor, the belt 3 or 103 accumulates an excessive number of unwrapped packs. This is another reason for supervising the transport of packs on the belt 3 or 103. As a rule, wrapped packs are removed from the packing machine at predetermined intervals whose length depends on the setting and speed of the packing machine.

One device for monitoring the feed of cigarette packs on the belt 3 is illustrated in FIG. 4. This device includes means for monitoring the width of gaps between successive packs. If the width of such gaps decreases to a predetermined value, for example, to zero, this indicates that the packs are piling up downstream of the monitoring station and that remedial steps (e.g., stoppage of the belt 3) must be undertaken in order to avoid defacing or damaging of packs. Instead of serving to stop the belt 3, signals produced in response to a reduction of the width of gaps between successive packs can be used to stop the machine which supplies packs to the belt 3 or to stop the supplying machine and the packing machine.

Referring to FIG. 4, in detail, that portion of the endless foraminous belt 3 which is illustrated in this Figure is located ahead of the suction chamber 55 shown in FIG. 1. The belt 3 travels above two longitudinally spaced rollers 1, 2 which are respectively mounted ahead of and behind a housing 7. This housing is connected to a suction conduit 9 containing a regulating valve 11 and connected to the suction side of a suction pump 12. The top wall of the housing 7 is located directly below the upper stretch of the belt 3 and is provided with a longitudinally extending slot or opening 8 which draws air when the pump 12 is driven. Such air passes through the openings 4 of the belt 3 and through the gaps 6 between successive unwrapped cigarette packs 5. The detector means of the monitoring device comprises a container or bellows 13 which is fixed to the bottom wall of the housing 7 and is also connected with one arm of a two-armed lever 14 which is fulcrumed in the housing 7, as at 14a. The other arm of the lever 14 carries a platelike actuating member 18 which can depress the movable contact 17 of a microswitch 16. Conductors 19, 21 connect the microswitch 16 in circuit with an energy source and with one or more signal generating or like devices, not shown. The microswitch 16 is mounted in the interior and on the bottom wall of the housing 7. The interior of the bellows 13 is completely sealed from the interior of the housing 7. Instead of being connected in circuit with a signal generating device (e.g., with a lamp or a bell), the microswitch 16 can be connected with the drive of the packing machine which receives packs 5 from the belt 3 or with the drive of the machine which supplies packs to the belt.

The operation

As long as the width of gaps 6 between successive packs 5 on the upper stretch of the belt 3 exceeds a predetermined minimum value (e.g., zero), the pump 12 can draw air through the gaps 6, openings 4 of the belt 3, slot 8 of the housing 7, the interior of the housing 7, conduit 9 and regulating valve 11 (which is assumed to be open). Pressure in the interior of the housing 7 then exceeds a minimum pressure which must be established before the bellows 13 can expand sufficiently to pivot the lever 14 in a clockwise direction, as viewed in FIG. 4, and to thereby close the microswitch 16 by way of the plate 18. If the packs 5 begin to pile up downstream of the roller 2, they form a column whose length increases toward and beyond the roller 2 whereby the width of the gaps 6 between the packs above the slot 8 decreases to zero so that the pump 12 merely draws air from the housing 7 and reduces the pressure therein below the aforementioned value at which the bellows 13 expands sufficiently to close the microswitch 16. As stated before, such closing of the microswitch 16 can result in generation of an optical signal, an audible signal or in stoppage of the belt 3 and/or machine which supplies packs to the belt. The signal produced on closing of the microswitch 16 can also serve to stop the packing machine which receives packs 5 from the belt 3.

The width of the slot 8 is a fraction of the width of the belt 3.

If the pump 12 is connected with the conduit 9 in such a way that it blows compressed air into the housing 7, the bellows 13 is replaced by a bellows 13a which is mounted between the fulcrum 14a and the plate 18. The expanding force of the bellows 13a is selected in such a way that it can maintain the lever 14 in the illustrated position (microswitch 16 open) when the width of gaps 6 suffices to permit escape of air which is blown by the pump 12 or another air compressing device. Air supplied by the conduit 9 then flows through the interior of the housing 7, slot 8, openings 4 and gaps 6 into the atmosphere. If the width of gaps 6 is reduced to a predetermined extent (for example, to zero), pressure in the housing 7 rises and the bellows 13a is compressed so that the lever 14 closes the microswitch 16 whereby the latter can initiate one or more of the aforementioned operations. The just described modified testing device is particularly suited for use in machines which manipulate relatively heavy packs or analogous articles or when the articles are fed by pneumatic means. In the latter instance, air issuing from the slot 8 into the gaps 6 can be used to assist transport of the packs 5 toward the turret of the packing machine, or such air can be used to form a cushion along the walls of the tube in which the packs are fed by pneumatic means. The valve 11 is preferably adjustable so that it enables the operator to regulate the pressure in the housing 7, regardless of whether the housing 7 constitutes a suction chamber or a plenum chamber. The valve 11 should be sufficiently sensitive to permit accurate adjustments of pressure in the housing 7 so as to insure that the microswitch 16 closes when the width of gaps 6 decreases to a predetermined value.

An important advantage of the monitoring device shown in FIG. 4 is that it is rugged and can stand long periods of use without any or with minimal maintenance and adjustment. However, if is equally within the purview of our invention to employ other types of devices which can monitor the feed of articles on the belt 3 or 103.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of our contribution to the art.

Claims

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

1. In a machine for applying wrappers around cigarette packs or analogous articles, a combination comprising a wrapping conveyor having a plurality of receptacles wherein the articles are accommodated during application of wrappers thereto; a first transporting conveyor for supplying articles to said receptacles; a second transporting conveyor for receiving wrapped articles from said receptacles, at least one of said transporting conveyors comprising a foraminous portion movable along a predetermined path and having an article-supporting first side and a second side; a variable-pressure chamber having at least one opening adjacent to said second side of said portion so that pressure changes in said chamber influence the friction between said one side and the articles, and means for varying the pressure in said chamber in dependency on the position of said wrapping conveyor.

2. A combination as defined in claim 1, wherein said chamber is a suction chamber.

3. A combination as defined in claim 1, wherein said means for varying the pressure in said chamber comprises a suction generating part, an air-compressing part and regulating means for connecting said chamber with one of said parts at a time so that said chamber is a suction chamber when connected to said suction generating part and a plenum chamber when connected to said air-compressing part.

4. A combination as defined in claim 1, further comprising means for programming the operation of said means for varying the pressure in said chamber.

5. A combination as defined in claim 1, wherein said one transporting conveyor has an intermediate portion and a discharge end and said chamber is adjacent to said discharge end, and further comprising monitoring means for detecting changes in the spacing between successive articles which are conveyed toward said chamber.

6. A combination as defined in claim 5, wherein said monitoring means comprises a device for conveying streams of air through said intermediate portion of said one conveyor upstream of said chamber and between successive articles at said first side of said intermediate portion so that the characteristics of said air streams are influenced by the relative positions of articles at said first side, and detector means for determining the characteristics of said air streams.

7. A combination as defined in claim 6, wherein said device comprises an air pump.

8. A combination as defined in claim 6, wherein said monitoring means further comprises a housing adjacent to said second side and having an opening adjacent to said intermediate portion, said device being arranged to convey streams of air through said housing, through said opening, through that part of said one conveyor which overlaps said opening, and through gaps between articles which are transported along said first side.

9. A combination as defined in claim 8, wherein the width of said opening is a fraction of the width of said intermediate portion.

10. A combination as defined in claim 8, wherein said opening is an elongated slot extending lengthwise of said intermediate portion.

11. A combination as defined in claim 8, wherein said detector means comprises a deformable container provided in said housing to undergo deformation whose extent is a function of the pressure in said housing and signal generating means operative to produce signals in response to that predetermined deformation of said container which is indicative of a predetermined distance between articles travelling along the opening of said housing.

12. A combination as defined in claim 11, wherein said signal generating means comprises electric switch means whose position changes in response to said predetermined deformation of said container.

13. Apparatus for monitoring changes in relative positions of a series of articles, particularly for scanning rows of cigarette packs during transport to the wrapping conveyor of a packing machine, comprising a foraminous conveyor arranged to move along a predetermined path and having an article supporting first side and a second side; a chamber having at least one opening adjacent to said path at the second side of said foraminous conveyor; a device for conveying air streams between the atmosphere and the interior of said chamber whereby said air streams pass through said foraminous conveyor and between the articles of the series at said first side so that the characteristics of said air streams are influenced by the relative positions of articles in said series; and detector means for determining the characteristics of said air streams.

14. Apparatus as defined in claim 13, wherein said device comprises a pump.

15. Apparatus as defined in claim 13, wherein the width of said conveyor exceeds the width of said opening.

16. Apparatus as defined in claim 13, wherein said opening is a slot extending lengthwise of said conveyor.

17. Apparatus as defined in claim 13, wherein said detector means comprises a deformable container arranged to undergo deformation whose extent is a function of the pressure in said chamber and signal generating means operative to produce signals in response to that predetermined deformation of said container which is indicative of a predetermined spacing between articles travelling along the opening of said housing.

18. Apparatus as defined in claim 17, wherein said container is provided in said chamber and said signal generating means comprises electric switch means whose position changes in response to said predetermined deformation of the container.