GB2141644A - Apparatus for applying adhesive to the backs of pads - Google Patents

Abstract

Apparatus for applying adhesive to the backs 26 of pads 126 consisting of stacked paper sheets, while the pads are held at a standstill in the pockets of an indexible turret 226, has a reciprocable carriage 1 with a row of roller-shaped applicators 2-7 therein and with discrete chambers 8-13 receiving portions of the respective applicators. All of the chambers receive adhesive from a common channel 14 wherein the supply of adhesive is replenished in response to signals which are generated by a level monitoring device. Each of the applicators applies a film of adhesive to a portion of the back of a pad. The flow of adhesive to and from the chambers 8-13 is controlled by pairs of rollers 23, 24. The surplus of applied adhesive is gathered in troughs next to the applicators and is returned by the applicators into the respective chambers for reuse. All of the applicators are rotated in a single direction, either in response to movement of the carriage relative to a pad or in response to starting of a gear motor which drives the applicators by way of toothed belts and pulleys. <IMAGE>

Description

SPECIFICATION Apparatus for applying adhesive to the backs of pads and the like The present invention relates to machines and production lines for making stationery products, especially exercise books, steno pads and the like. More particularly, the invention relates to improvements in apparatus for applying films of adhesive to selected edge faces of successive stacks which are being converted into pads or analogous stationery products.

It is well shown to apply films of adhesive to selected edge faces of stacks of paper sheets in order to hold the sheets together and to allow for folding of sheets relative to one another as well as for separation of sheets from the remainder of the pad.

For example, German Offenlegungsschrift No. 33 01 032 discloses an apparatus which applies adhesive to selected edge faces of stacks of paper sheets while such stacks are confined in the radially extending pockets of a turret-shaped conveyor. The arrangement is such that the selected edge face of the stack which is about to receive adhesive extends outwardly beyond the periphery of the turret so that it is accessible to an adhesiveapplying roller which must be caused to roll along the the entire edge face while drawing adhesive from a chamber or the like. A drawback fo such adhesive applying apparatus is that the single roller must cover a considerable distance in order to coat the entire selected edge face of the stack of sheets at the adhesive applying station.This reduces the output of the production line in which the apparatus is put to use because the applcation of adhesive takes place while the conveyor is at a standstill. The situation is aggravated because, at the time of the application of adhesive, the stacks in the pockets of the conveyor are much larger than the ultimate products, i.e.

each such stack is subdivided into several smaller stacks or pads subsequent to the application of adhesive to one of its edge faces. In other words, the distance which the single roller of a conventional adhesive applying apparatus must cover during each interval of idleness of the conveyor is several times the length of the adh sive-coated back of a single pad.

The invention is embodied in an apparatus for applying a flowable adhesive to selected edge faces of stacks of paper sheets or the like. The apparatus comprises an indexible turret or other suitable means for advancing successive stacks to a predetermined position in which the selected edge face of the stack occupying such position is located at an adhesive applying station, a support (preferably a reciprocable carriage) which is adjacent to the adhesive applying station, a row of rotary adhesive applcators mounted in the support, a discrete source of adhesive adjacent each of the applicators, a single adhesive feeding device which serves to apply adhesive to all of the sources, and means for moving the support with reference to the adhesive applying station so that the applcators transfer adhesive from the respective sources to portions of the selected edge face of the stack occupying the predetermined position. In accordance with a presently preferred embodiment of the invention, the sources and the feeding device are provided in the support. Each source has an adhesive containing chamber which receives a portion of the respective applicator, and the feeding device has a channel which communicates with each of the chambers. The channel preferably includes enlarged portions between at least some of the chambers to reduce the likelihood of excessive agitation and splashing of flowable adhesive as a result of movement of the support relative to the stack which occupies the predetermined position.

The apparatus preferably further comprises a pair of rollers for each applcator. The rollers of each pair are installed in the support, they flank the respective applicator and they define therewith gaps of variable width for the flow of adhesive from and into the respective chambers. For example, each roller can have a flat in its peripheral surface so that the width of the gaps can be changed by changing the angular positions of the respective rollers. The same or a similar result can be achieved by using eccentrically mounted rollers. The apparatus preferably also comprises means for jointly changing the angular positions of the rollers of each pair, and such position changing means can comprise a discrete link train for each pair of rollers.

The support can be assembled of two preferably separable sections including an upper section and a lower section. The aforementioned channel is preferably machined into or otherwise formed in the upper section, and the lower section is preferably provided with a second channel which communicates with the channel of the upper section and with passages leading therefrom to the adhesive containing chambers.Still further, the apparatus can be provided with passages and/or other suitable means for returning adhesive to the channel in the upper section of the support, and with troughs or other suitable means for collecting the surplus of adhesive adjacent to the applicators so that the applicators can transfer the gathered surplus from the respective troughs into the respective chambers (by way of one of th aforementioned pairs of gaps) when they are caused to rotate relative to the support.

Means is preferably provided to monitor the supply of adhesive in the channel of the upper section of the support. Such monitoring means can serve to effect delivery of adhesive from a suitable main source of adhesive to the channel in the upper section whenever the supply of adhesive in such channel descends below a predetermined minimum permissible or acceptable level. The monitoring means can comprise a spark plug which can generate sparks only when it is not immersed in the supply of adhesive in the channel of the upper section of the support.

The support can be reciprocated by a suitable prime mover, such as the main motor of a production line wherein the improved apparatus is put to use, by way of a cam and follower arrangement.

The apparatus further comprises drive means for rotating all of the applicators in a predetermined direction. The drive means can comprise a gear motor and belt means receiving motion from the gear motor to rotate the applicators in the predetermined direction while the support is caused to move in a first direction, and the applicators can be rotated in the same direction in automatic response to movement of the support in a second direction counter to the first direction. The shafts for the applicators can be provided with pulleys for the belt means (preferably one or more toothed belts) and with freewheels between the pulleys and the respective shafts.

Deflecting means for the belt means can be provided on a housing which does not reciprocate with the support.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved 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.

FIG. 1 is a schematic longitudinal sectional view of a support for a row of roller-shaped adhesive applicators in the apparatus of the present invention, the means for transporting stacks of paper sheets to and from the adhesive applying station being shown by phantom lines; FIG. 2 is a schematic plan view of the support, of the drive means for the applicators and of the means for guiding and reciprocating the support; FIG. 3 is an enlarged sectional view as seen in the direction of arrows from the line A-A of FIG. 2; and FIG. 4 is a sectional view as seen in the direction of arrows from the line i3-B of FIG.

3.

Referring to FIGS. 1 and 2, there is shown an apparatus which serves to apply adhesive to selected edge faces 26 of successive stacks 1 26 of paper sheets which are advanced stepwise by an indexible turretshaped conveyor 226. To this end, the periphery of the conveyor 226 has radially extending pockets each of which can receive a stack 1 26 in such a way that the selected edge face 26 (i.e. the edge face which is to be coated with a film of adhesive) extends outwardly beyond the respective pocket. Reference may be had. for example, to U.S. Pat.No. 4 1 57 821 which shows such a conveyoras well as to commonly owned copending patent application Serial No. 418,211 which shows the turret-shaped stack advancing means as well as other means for manipulating stacks of paper sheets for the purpose of converting each stack into a stationery product.

The apparatus further comprises a support 1 in the form of an elongated carriage which is reciprocable in directions indicated by the double-headed arrow A. The carriage 1 is closely or immediately adjacent to the station for the selected edge face 26 of a stack 1 26 which is then located at the adhesive-applying station while the turret 226 is at a standstill.

As can be best seen in FIG. 1, the carriage 1 supports a row of five equidistant rotary adhesive applicators 2, 3, 4, 6, 7 each of which is a relatively narrow roller rotatable about a horizontal axis which is normal to the plane of FIG. 1. Furthermore, the carriage 1 comprises five discrete sources of adhesive, one for each of the applicators 2, 3, 4, 6 and 7. Each such source is an integral part of the carriage 1 and has an adhesivecontaining chamber.The chambers are shown at 8, 9. 11, 12 and 13, and each of these chambers accommodates a portion of the respective applicator so that a relatively small part of the peripheral surface of each applicator extends dowowardly, as viewed in FIG. 1, beyond the underside of the carriage 1 in order to be movable into contact with the selected edge face 26 of the stack 1 26 at the aforementioned adhesive-applying station while the turret 226 is at a standstill.

Still further, the carriage 1 is integral with an adhesive feeding device having an elongated channel 14 which is machined directly into the material of the carriage and communicates with each of the five chambers 8, 9, 11, 1 2 and 1 3. Those portions of the channel 14 which extend between neighboring chambers are formed with enlargements 16, 17, 18 and 1 9 which are filled with adhesive and serve to reduce the likelihood of swilling or sloshing of adhesive in response to movements of the carriage 1 in directions which are indicated by the arrow A. The carriage 1 is arranged to move rapidly in each of the indicated directions in order to reduce the interval of idleness of the turret 226 for the purpose of applying a satisffactory adhesive film-to the edge face 26 at the adhesive applying station.

The carriage 1 is further formed with a bore 21 which can receive adh sive from a main source of supply 1 21 by way of a flexible conduit 221 (e.a., a rubber hose) in response to opening of a valve 321 which is controlled by a level detector 421 in the channel 14.

The arrangement is such that the level detector 421 causes the valve 321 to open for a certain interval of time when the supply of adhesive in the channel 14 drops below a preselected level. The level detector 421 can comprise any suitable level monitoring means, e.g. a spark plug which can generate a spark as soon as its electrodes are not immersed in the adhesive, i.e. as soon as the supply of adhesive in the channel 14 descends before the aforementioned preselected level. The generation of a spark entails an opening of the valve 321 and the admission of fresh adhesive into the channel 14 and thence into the chambers 8, 9, 11, 12 and 13.The bore 22 in the carriage 1 serves to permit for the passage of conductor means from the level detector 421 to the valve 321, i.e., for transmission of signals which initiate an open ing of the valve 321 and the admission of adhesive into the channel 14 when the need arises. The turret 226 is provided with or contains means for shifting the stack 1 26 at the adhesive applying station slightly outwardly so that the selected edge face 26 of such stack is readily accessible to the applicators 2, 3, 4, 6 and 7 when the carriage 1 is caused to perform a working stroke and to simultaneously maintain the roller-shaped applicators in contact with the edge face 26.

As shown in the upper portion of FIG. 2, the carriage 1 comprises upwardly extending bearing sleeves 27, 28, 29 which are slidable along two parallel guide rods 31, 32 longitudinally of the edge faces 26 of the stack 126 at the adhesive applying station. The guide rods 31, 32 are secured to brackets 33, 34 which, in turn, are secured to an elongated traverse 36 extending between and secured to two frame members or cheeks 37 and 38. As can be seen in FIG. 3 for the frame member 37, these frame members are clamped to circular cylindrical stubs 39 forming part of a shaft 40 having a square or other non-circular outline and mounted in a frame or housing 41.The shaft 40 can be rocked by nonillustrated means clockwise and counterclockwise, as viewed in FIG. 3, so as to move the carriage 1 toward or away from the selected edge face 26 of the stack 1 26 at the adhesive applying station. FIG. 3 shows the applicators (only the applicator 6 can be seen) in actual contact with the edge face 26.

The drive means for rotating the applicators 2, 3, 4, 6 and 7 in a predetermined direction comprises a gear motor 42 which is mounted in or on the housing 41 so that it can rock back and forth with the carriage 1 about the axis of the shaft 40. The output element 43 of the motor 42 is a pinion which drives a main toothed belt 44 (see FIG. 2) which is trained over and deflected by idler rollers or pulleys 46, 47 mounted in the housing 41.

The toothed belt 44 is further trained over toothed pulleys 48, 49 and 51 which respectively serve to transmit torque to the three centrally located applicators 3, 4 and 6. The toothless side of the belt 44 engages a first additional deflecting roller or pulley 52 which is mounted on the carriage 1 between the pulleys 48, 49 and a second additional deflecting roller or pulley 53 which is mounted on the carriage 1 between the pulleys 49 and 51.

The two outermost applicators 2 and 7 are respectively driven by discrete toothed belts 54 and 56 which are shown in FIG. 2. The belt 54 receives torque from a toothed pulley 57 which is coaxial with the pulley 48 for the applicator 3 and drives a toothed pulley 58 which is coaxial with and transmits torque to the applicator 2. The belt 56 is trained over a pulley 59 which is caoxial with and receives torque from the pulley 51 and this belt drives a pulley 61 which is coaxial with and transmits torque to the applicator 7. The pulleys 48, 49 and 51 surround freewheels 62 which enable the respective applicators 3, 4, 6 to rotate relative to the corresponding pulleys and vice versa.One of the freewheels 62 is shown in FIG. 3; this freewheel ensures that the shaft 63 for the corresponding applicator 6 and pulleys 51, 59 can rotate with the applicator 6 while the applicator rolls along the adjacent edge face 26 in response to movement of the carriage 1 in one of the directions which are indicated by the doubleheaded arrow A. The mounting of the other two freewheels 62 is analogous. The shaft 63 is rotatable in antiffriction ball or roller bearings 64, 66 which are installed in the carriage 1.The means for reciprocating the carriage 1 in the directions indicated by the arrow A comprises a link or lever 67 which receives motion from a cam and follower drive 1 67 which, in turn, receives motion from the main prime mover 267 of the machine which includes the improved adhesive applying apparatus, e.g. a production line which turns out steno pads, exercise books and analogous stationery products.

In FIG. 2, the bracketed reference character 2 indicates that the applicator 2 is coaxial with and is located behind the pulley 58. The same applies for the bracketed numerals 3, 48, 4, 6, 51 and 7. As can be seen in FIG. 3 for the applicator 6, each such applicator is mounted on a shaft (note the aforementioned shaft 63) which is mounted in the carriage 1 in antifriction bearings (64, 66) and is further fixedly connected with one of the pulleys 48, 49, 51 by way of the respective freewheel 62. The shaft 63 of FIG. 3 is further rigidly connected with the pulley 59 for the belt 56 which drives the applicator 7 via pulley 61.

The shaft for the applicator 4 merely carries the corresponding pulley 49 and the respective freewheel 62, and the shaft for the appli cator 3 carries the pulleys 48, 57 as well as the third freewheel 62.

The carriage 1 is preferably assembled of two separable portions or sections including an upper section 68 (see particularly FIG. 3) and a lower section 69. The channel 14 is machined into or otherwise formed in the upper section 68, and the lower section 69 has a second channel 71 which is coextensive with and communicates with the channel 14 along the entire length of each of these channels. The channel 71 has or communicates with downwardly extending passages 72 which connect it with the chambers 8, 9, 11, 1 2 and 1 3. In other words, the channel 14 communicates with such chambers by way of the channel 71 and passages 72.Each of the chambers 8, 9, 11, 12 and 1 3 is a relatively narrow arcuate compartment (see FIG. 4 which shows the chamber 12) receiving the major portion of the respective applicator (6 in FIG. 4) and having two outlets or inlets at the opposite sides of the respective applicator.

The flow of adhesive into and from the chambers 8, 9, 11, 12, 1 3 at the underside of the carriage 1 is controlled by pairs of rollers 23, 24 which are provided with peripheral flats (note the flats 82, 83 in FIG. 4) so that changes in angular positions of the rollers 23, 24 entail changes in the rate at which the adhesive can flow from or into the respective chambers. The rollers 23, 24 are mounted in the carriage 1 adjacent to its underside.

Referring again to FIG. 3, it will be noted that the internal surface 73 of the lower section 69 of the carriage 1 is inclined and slopes downwardly and away from the edge face 26 at the adhesive applying station before the housing 41 is tilted to the operative position in which the surface 73 below the channel 71 is horizontal. When the surface 73 is horizontal, the upper level of the supply of adhesive in the channel 14 is the same as in each of the chambers 8,9,11, 12 and 13.

When the carriage 1 is pivoted toward the edge face 26 of the stack 1 26 at the adhesive applying station and is caused to move in one of the directions which are indicated by the arrow A, the applicators 2, 3, 4, 6 and 7 draw films of adhesive from the respective chambers 8, 9, 11, 1 2 and 1 3 and transfer such films to the edge face 26 while rotating in a predetermined direction (arrow B in FIG.

4). At such time, the gear motor 42 is idle and the pulleys 48, 49, 51 rotate the applicators 3, 4, 6 because they roll along the belt 44. The pulleys 57, 59 rotate with the shafts for the applicators 3, 6 and drive the adjacent applicators 2, 7 in the same direction (arrow B). At such time, the applicators draw adhesive from the respective chambers through the gaps between the peripheral surfaces of such applicators and the peripheral surfaces of the respective rollers 23.In other words, the angular positions of the rollers 23 and their flats 82 determine the rate of outflow of adhesive from the respective chambers 8, 9, 11, 1 2 and 1 3. The surplus of withdrawn adhesive accumulates in collecting means in the form of suitably configurated gathering troughs 74 which are adjacent to the underside of the carriage 1 and from which the surplus is returned into the corresponding chambers 8, 9, 11, 1 2 and 1 3 by the respective applicators 2, 3, 4, 6 and 7 by way of gaps between such applicators and the respective rollers 24. As a rule, the selected angular positions of the rollers 23 and 24 are such that the gap between each roller 23 and the corresponding applicator is narrower than the gap between each roller 24 and the corresponding applicator.This ensures that the adhesive which is being delivered from a trough 74 back into the respective chamber encounters relatively little resistance.

Still further, the carriage 1 is provided with bores or passages 76 which allow for return flow of adhesive from the chambers 8, 9, 11, 12 and 13 into the channel 14 when the pressure of adhesive in the chambers exceeds a certain maximum permissible value. One such passage 76 is shown in each of FIGS. 3 and 4. The passages 76 are provided in the upper section 68 of the carriage 1. FIG. 3 further shows a shaft seal 77 for the shaft 63 which prevents uncontrolled escape of adhesive from the corresponding chamber 1 2 toward the antifriction bearings 64, 66. Similar shaft seals are also provided adjacent to the chambers 8, 9, 11 and 1 3. The opposite axial end of each of the applicators is adjacent to a disc 79 (see FIG. 3) which has a stub 78 extending into a blind bore in the lower section 69 of the carriage 1.The disc 79 actually extends into a depression in the adjacent end face of the applicator 6 of FIG. 3 to form therewith a labyrinth seal which prevents uncontrolled escape of adhesive from the chamber 1 2 at the respective axial end of the applicator. Similar labyrinth seals are preferably provided adjacent to one end face of each of the other four applicators.

In order to adjust the width of gaps between the applcators and the respective pairs of rollers 23, 24, the apparatus of the present invention preferably comprises means for simultaneously changing the angular positions of the two associated or paired rollers. Such adjusting or position changing means comprises a link train including two levers 84, 86 which are respectively connected to the shafts for the rollers 23, 24 and a connector 87 which is articulately connected to the levers 84, 86 (see FIG. 4). The right-hand end portion of the lever 84 shown in FIG. 4 can receive motion from a common adjustor for all of the five pairs of rollers 23, 24 to simultaneously change the orientation of the flats 82 and 83 and hence the width of the corresponding gaps between each applcator and the respective pair of rollers 23, 24.

It is advisable to ensure that the applicators 2, 3, 4, 6 and 7 always rotate in a single direction irrespective of whether they receive torque in response to movement of the carriage 1 relative to the station for the stack 1 26 which is to be coated with adhesive or from the prime mover 42 in the housing 41.

This is achieved as follows: When the carriage 1 is moved toward the edge face 26 of a stack 1 26 at the adhesive applying station, the exposed portions of the applicators 2, 3, 4, 6 and 7 engage the edge face and roll therealong in response to movement of the carriage 1 in a first direction (under the action of the lever 67). At such time, the three freewheels 62 are not effective to allow the applicators 3, 4, 6 to rotate relative to the corresponding pulleys 48, 49 and 51 because the main belt 44 is then at a standstill and the pulleys 48, 49 and 51 simply roll therealong.Such rolling of the pulleys 48, 49, 51 (which share the forward movement of the carriage 1 whereas the pinion 43 for the belt 44 is mounted on the stationary housing 41 for the motor 42) sets the corresponding applicators 3, 4, 6 into rotary motion through the medium of the respective freewheels 62.

The shafts for the applicators 3, 6 drive the belts 54, 56 which, in turn, rotate the outermost applicators 2 and 7 in the same direction (arrow B). The peripheral speed of all five applicators is the same.

(i.e., the motor 42 is idle) When the carriage 1 thereupon performs a return strokeandthe applicators are lifted off the edge face 26, the motor 42 is on and drives the pulleys 48, 43, 51 by way of the pinion 43 and belt 44 in the same direction in which the applicators were rotated during the forward stroke of the carriage. The motor 42 must drive the pulley 44 at a speed which exceeds the speed of return movement of the carriage 1. This is possible due to the provision of freewheels 62.

The aforementioned valve 321 in the conduit 221 can be replaced with a pump which is coupled to its motor in response to signals from the detector 421 so that the pump then delivers adhesive to the channel 1 4 via bore 21 in the carriage 1.

An important advantage of the improved apparatus is that the carriage 1 must perform relatively short strokes because each of the applicators 2, 3, 4, 6, 7 applies adhesive to a relatively short portion of the edge face 26.

Thus, the interval which is required to completely coat an edge face with an adequate film of adhesive is reduced to a fraction of the interval which is required in a conventional apparatus employing a single applicator which must roll along the full length of the edge face. By shortening the interval which is required for the application of adhesive, the apparatus enables the machine or production line to turn out a larger number of stationery products per unit of time.

Another advantage of the improved apparatus is that it applies the adhesive economically because the surplus is gathered by the troughs 74 and is automatically returned into the respective chambers for renewed use.

Automatic replenishing of the supply of adhesive in the channel 14 also constributes to more reliable operation of the improved adhesive applying apparatus, and the adjustabilty of the widths of gaps between the applicators and the respective pairs of rollers 23, 24 ensures that the apparatus can be adjusted to operate satisfactorily with more or less viscous adhesives as well as that the rate of application of adhesive can be selected within a desired range.

The novel drive means for the applicators enables the apparatus to hold the applicators to rotation in a single direction with all of the aforediscussed advantages of such mode of operation.

Claims (28)

1. Apparatus for applying adhesive to selected edge faces of stacks of paper sheets or the like, comprising means for advancing successive stacks to a predetermined position in which the selected edge face of the stack occupying such position is located at an adhesive applying station; a support adjacent to said station; a row of rotary adhesive applicators mounted on said support; a discrete source of adhesive adjacent to each of said applicators; a single adhesive feeding device arranged to supply adhesive to all of said sources; and means for moving said support with reference to said station so that said applicators transfer adhesive from the respective sources to the selected edge face of the stack occupying said position.

2. The apparatus of claim 1, wherein said sources and said feeding device are provided in said support.

3. The apparatus of claim 2, wherein each of said sources has a chamber receiving a portion of the respective applicator and said device has a channel which communicates with each of said chambers.

4. The apparatus of claim 1, wherein said support includes a reciprocable carriage.

5. The apparatus of claim 1, wherein each of said sources has an adhesive containing chamber for a portion of the respective applicator and said device has a channel communicating with said chambers and having enlarged portions disposed between at least some of said chambers to reduce the likelihood of agitation of adhesive as a result of movement of said support relative to the stack occupying said position.

6. The apparatus of claim 1, wherein each of said sources has an adhesive containing chamber rpovided in said support and receiv ing a portion of the respective applicator, and further comprising a pair of rollers for each of said applicators, said pairs of rollers being installed in said support, flanking the respective applicators and defining therewith gaps of variable width for the flow of adhesive into and from the respective chambers.

7. The apparatus of claim 6, wherein each of said rollers has a peripheral surface provided with a flat so that the width of said gaps changes in response to changes in angular positions of the respective rollers.

8. The apparatus of claim 7, further comprising means for jointly changing the angular positions of the rollers of each of said pairs.

9. The apparatus of claim 8, wherein each of said position changing means comprises a link train.

10. The apparatus of claim 1, wherein said sources are provided in said support and each thereof has an adhesive containing chamber receiving a portion of the respective applicator, said device being provided in said support and including a first channel communicating with each of said chambers, said support including a first section and a second section and said first channel being provided in said first section and said second section having a second channel which communicates with said first channel and passages connecting said second channel with said chambers so that such chambers receive adhesive from said first channel by way of said second channel.

11. The apparatus of claim 10, wherein said sections of said support are separable from one another.

1 2. The apparatus of claim 1, further comprising means for returning the adhesive from said sources to said device.

1 3. The apparatus of claim 1, further comprising means for collecting the surplus of adhesive which is applied by said applicators to the selected edge face of the stack occupying said position.

14. The apparatus of claim 13, wherein said collecting means comprises a trough adjacent to each of said applicators, each of said applicators being arranged to transfer adhesive from the respective trough back into the respective source in response to rotation of the applicator.

1 5. The apparatus of claim 1, further comprising means for monitoring the level of adhesive in said device.

1 6. The apparatus of claim 15, further comprising a main source of adhesive, said monitoring means being arranged to effect delivery of adhesive from said main source to said device when the adhesive in said device descends below a preselected level.

17. The apparatus of claim 15, wherein said monitoring means comprises a spark plug arranged to generate sparks when the adhesive in said device descends below a preselected level.

1 8. The apparatus of claim 1, further comprising prime mover means and cam and follower means for transmitting motion from said prime mover means to said support.

1 9. The apparatus of claim 1. further comprising drive means for rotating all of said applicators in a predetermined direction.

20. The apparatus of claim 19, wherein said support comprises a carriage which is reciprocable relative to the edge face of the stack occupying said position, said drive means comprising means for rotating said applicators while said carriage moves in a first direction and said applicators being rotatable in said predetermined direction in response to movement of said carriage in a second direction counter to said first direction.

21. The apparatus of claim 20, wherein said drive means further comprises shafts for said applicators. pulleys provided on at least some of said shafts, freewheels interposed between said pulleys and the respective shafts, and endless belt means trained over said pulleys.

22. The apparatus of claim 21, wherein said belt means includes at least one toothed belt.

23. The apparatus of claim 21, wherein said drive means further comprises a gear motor arranged to drive said belt means.

24. The apparatus of claim 21, further comprising deflecting means for said belt means and a housing supporting said deflecting means.

25. Apparatus for applying adhesive, particularly for applying adhesive to selected edge faces of stacks of paper sheets or the Ike, comprising a support, a plurality of rotary adhesive applicators in said support, means defining in said support an adhesivecontaining chamber for each of said applicators, each of said chambers receiving a portion of the respective applicator, and a pair of rollers for each of said applicators, said pairs of rollers being installed in said support, flanking the respective applicators and defining therewith gaps of variable width for the flow of adhesive into or from the respective chambers.

26. The apparatus of claim 25, wherein at least one roller of each of said pairs of rollers has a peripheral surface provided with a flat so that the width of the respective gap varies in response to a change in the angular position of the corresponding roller.

27. The apparatus of claim 26, further comprising means for jointly changing the angular positions of the rollers of each pair of rollers.

28. Apparatus for applying adhesive to selected edge faces of stacks of paper sheets or the like, substantially as herein described with reference to the accompanying drawings.