Adhesive applicator apparatus

Abstract: The invention relates to an adhesive applicator apparatus having an adhesive applicator roller (16) rotatable in an adhesive tank (12) and a doctor blade assembly (18) associated with the applicator roller. So that the adhesive in the tank does not become aerated, the applicator roller (16) is located wholly above the level of adhesive in the tank (12), and a rotatable pick-up disc (20) is provided to feed adhesive to a receiving reservoir (24) formed in the doctor blade assembly (18).

Description: The invention relates to adhesive applicator apparatus primarily but not exclusively for use in association with cigarette making machinery. Various kinds of adhesive applicator apparatus for spreading adhesive evenly across a paper web are in use at present in a variety of industries. However, most of these suffer from at least one of several common drawbacks. For example, in the kind of adhesive applicator apparatus having an adhesive pick-up roller partly immersed in a quantity of adhesive, and having a doctor blade spaced from an operative part of the pick-up roller to produce an even thickness of adhesive on said operative part, one particular drawback is that the constant entry of the roller surface into the adhesive carries with it a quantity of air which tends to aerate the adhesive so that this causes problems in connection with its even distribution across the paper web. A further drawback is that if a particle of material, be it of grit or of solidified adhesive for example, becomes lodged in the gap between the operative part of the pick-up roller and the doctor blade, this produces a dry line around the pick-up roller and a dry line along the subsequently coated paper web. Another drawback of most known types of adhesive applicator apparatus is that changes of viscosity of the adhesive being used can seriously affect the operation of the apparatus. US-A-3389684 (Talbot) discloses a hot melt glue applicator which includes a pick-up gear which rotates within a trough of glue to pick-up glue which is passed to an applicator roller and which comprises the features included in the preamble of Claim 1. The invention aims to provide an adhesive applicator apparatus which will not tend to aerate the adhesive to any significant extent during the operation of the apparatus and which will be tolerant to a range of viscosity of the adhesive. The main advantage of reducing any tendency to aerate the adhesive to a far lesser extent is that fewer problems arise in connection with the even distribution of adhesive across the paper web. The present invention provides adhesive applicator apparatus as set out in the accompanying Claim 1. One way of carrying out the invention is described in detail below with reference to drawings which illustrate one specific embodiment, in which:- Figure 1 is a schematic perspective view of adhesive applicator apparatus embodying the invention, Figure 2 is a diagrammatic side view of the apparatus, and Figure 3 is a detail of construction which will be referred to, Figure 4 is a view similar to Figure 2 and illustrating a different embodiment of the invention, Figure 5 is a view of a component part of the apparatus, looking in the direction of arrow 5 in Figure 4, Figure 6 is an exploded view of the apparatus, and Figure 7 is a perspective view looking into an adhesive tank forming part of this embodiment. Referring now to Figures 1 to 3 of the drawings, the apparatus there illustrated is an adhesive applicator apparatus for use in association with cigarette making machinery. It is provided for spreading adhesive evenly across a paper web 10 to be used for applying filters to cigarettes. The apparatus includes an adhesive tank 12, a level control assembly 14 communicating with said tank, an applicator roller 16, and a doctor blade assembly, generally indicated 18, mounted in the tank to act against the applicator roller. Referring in particular to Figure 2, it will be seen that although the applicator roller 16 is rotatably mounted in the tank it is located wholly above the level of the adhesive in said tank. However, at one end of the applicator roller there is located an adhesive pick-up disc 20 which is arranged to rotate with said roller, the pick-up disc being partly immersed in the adhesive. A portion of the pick-up disc is flanked by a U-shaped element 22 depending from the doctor blade assembly 18, said U-shaped element forming a channel up which the disc 20 propels a quantity of adhesive which is then able to flow into a slot 24 constituting a receiving reservoir forming part of the doctor blade assembly, the adhesive flowing in through a flow passage 23 communicating with the rear of said slot. Immediately above the slot comprising the receiving reservoir, there are located three closely spaced grooves 26 in the part-circular face of the doctor blade assembly. Immediately above said grooves there is a further slot 28 which forms an adhesive return reservoir. Above and below each groove 26 there are narrow lands comprising primary doctor blades 30 closely spaced from the operative part of the applicator roller 16. A part of the assembly immediately above the slot 28 forming the adhesive return reservoir comprises a final doctor blade 32. It will be understood that, as shown by the arrows in Figure 2, the adhesive picked up by the pick-up disc 20 is forced inwardly along the receiving reservoir and is dragged into the narrow gaps formed between the primary doctor blades and the operative surface of the roller. The adhesive is made to flow laterally, that is to say along the slot 24 to extend across the full width of the applicator roller, by the force of the adhesive flow up the U-shaped element 22. The adhesive which flows into the return reservoir 28 is able to flow directly back into the reservoir of adhesive in the tank from an end of said return reservoir remote from the pick-up disc 20. As indicated by chain-dotted lines in Figure 1, a top cover shrouds the upstanding portion of the pick-up disc 20. A particular advantage of adhesive applicator apparatus as described above is that the pick-up disc will tend to aerate the adhesive in the tank to a far lesser extent than a conventional pick-up roller. It will also be understood that the adhesive being used at any time is that at the pick-up disc end of the tank 12. The adhesive in the tank is replenished by the level control assembly 14 at the opposite end of the tank so that there will tend to be no build-up of aerated adhesive in the tank. Referring now to Figure 3, this illustrates a detail of the applicator roller 16. As shown, the roller has plain bands 34 at each end. The doctor blade bears against said plain bands so that adhesive is not distributed on these parts of the roller. In addition, the roller has a central circumferential line 36 of the same diameter as the plain bands 34 so that this also is wiped clean by the doctor blade. The areas of the roller between the central circumferential line 36 and the respective plain bands 34 are of very slightly smaller diameter than said bands and central line, the arrangement being such that throughout the operation of the apparatus there is produced an even coating of adhesive on those areas of the roller, the thickness of the coating depending on the spacing of the doctor blade therefrom, that is to say on the depth of the areas between the line 36 and bands 34. However, in addition to the plain bands 34 and central circumferential line 36 at the doctor blade contacting diameter of the roller there are two ridges 38, these extending in chevron fashion from the central circumferential line 36 as shown. The purpose of these angled ridges is to act as sweeper elements which will act on any particles of material, be they of grit or of solidified adhesive, which might otherwise become lodged in the gap between the operative part of the roller and the doctor blade. Such particles of material acted on by said angled ridges are quickly swept towards the opposite ends of the roller from where they are returned to the bottom of tank 12. Referring now to Figures 4 to 7, in a modified form of the invention basically similar to that described above the doctor blade assembly 118 is located in the adhesive tank 112 by means of pivotal mounting means comprising a pair of laterally spaced ball and socket arrangements generally indicated 140. Each ball and socket arrangement 140 comprises a ball member 139 formed on a wall of the tank and a socket formation 141 formed on the doctor blade assembly 118. Each socket formation includes a ring 143 of an elastomeric material, the arrangement being such that when the socket formations have been pressed onto the respective ball members, they are retained thereon by the resilience of the rings 143. The doctor blade assembly is acted on in a lower region by resilient means comprising a slidably located abutment member 119 acted on by a coil compression spring 121. The doctor blade assembly in this case is provided with slipper elements 115 at each end which act against abutment surfaces 117 at the opposite ends of the operative part of the applicator roller 116. In this embodiment, the doctor blade assembly is formed with a slot 124 comprising a receiving reservoir and immediately above it a further slot 128 which forms an adhesive return reservoir. A part of the assembly immediately above the slot 128 forming the adhesive return reservoir constitutes a final doctor blade 132. There is but a single primary doctor blade 130 between the slots 124 and 128 which form the receiving and return reservoirs. The pick-up disc 120, which is associated with the applicator roller to rotate with it, is located in close proximity to one end of the doctor blade assembly. The arrangement is such that the adhesive which is picked up on the adjacent flank of said disc is dragged into the gap between disc and doctor blade and is able to flow into the open end of the slot 124 comprising the receiving reservoir. The adhesive is caused to flow along the slot by the pressure of the adhesive in the gap between the pick-up disc and doctor blade assembly. In this embodiment of the invention there is a pick-up limiting doctor blade 123 of bifurcated form associated with the pick-up disc 120, this being so closely spaced from both the periphery and from the flank of said pick-up disc adjacent the doctor blade assembly 118 that the rate of flow of adhesive into the slot 124 comprising the receiving reservoir is limited and only slightly in excess of that required to coat the paper web contacting the applicator roller. Consequently, the amount of adhesive being returned from the doctor blade assembly 118 to the supply of adhesive in the tank is relatively small. (The arrow beneath the pick-up limiting doctor blade in Figure 6 indicates the way in which the adhesive picked up by the pick-up disc is caused to be spread thinly and evenly on the flanks of said disc. This view also indicates the facility with which, when the pick-up disc top cover and the applicator roller and associated disc have been removed, the doctor blade assembly 118 can very easily be removed for cleaning of the apparatus). As indicated by arrows in Figure 4, adhesive return passages 142 extend through the ball and socket arrangements 140 and connect the adhesive return reservoir formed by the slot 128 to an adhesive return port 144 which opens below the level of the adhesive in the tank. Thus there is provided adhesive applicator apparatus which it has been found can operate for long periods of time without being prone to problems caused by aeration of the adhesive. The fact that aeration of the adhesive can only be caused by the relatively narrow pick-up disc entering the supply of adhesive in the tank reduces aeration significantly. The fact that in the Figure 4 to 7 construction the amount of adhesive being fed to the receiving reservoir of the doctor blade assembly is controlled by the pick-up limiting doctor blade associated with the pick-up disc results in a relatively small amount of adhesive being returned to the adhesive tank throughout the operation of the device and contributes to the overall reduction of aeration of the adhesive. It has also been found that apparatus embodying the invention is tolerant of wide ranging variations of viscosity of adhesive being used, that is to say works well with a number of different adhesives. Various modifications may be made. For example, whilst it will generally be most convenient for the pick-up disc to be associated with the applicator roller and to rotate with it, this is not essential. The pick-up disc could be separately mounted, and driven from the applicator roller for example, whilst still being arranged to feed adhesive to the receiving reservoir forming part of the doctor blade assembly. In this way the pick-up disc need not project above the applicator roller. A pick-up limiting doctor blade could be fitted to the apparatus illustrated in Figures 1 to 3. Likewise, the applicator roller of the Figure 4 to 7 embodiment could be provided with at least one angled ridge acting to sweep sideways any particles of material which might otherwise become lodged in the gap between the operative part of said roller and the doctor blade assembly, as illustrated in Figures 1 and 3. Although for the purpose of simple illustration the ridges 38 in Figures 1 and 3 are shown to be continuous ridges, this is not essential and it will be understood that the or each angled ridge could be a discontinuous ridge composed of a plurality of angled ridge elements at circumferentially spaced locations around the applicator roller, successive ridge elements overlapping each other across the operative part of said roller. It will be understood that whilst an adhesive applicator apparatus embodying the invention is especially useful in association with cigarette making machinery it is not exclusively for such use. An applicator apparatus embodying the invention could be used in the cardboard box making industry for example.

Claims: Adhesive applicator apparatus including a rotatable applicator roller (16, 116), an adhesive tank (12, 112) for the supply of adhesive to the roller and at least one doctor blade operatively associated with said applicator roller, the applicator roller (16, 116) being arranged so as to be located wholly above the level of adhesive in said tank and the apparatus also including an adhesive pick-up disc (20, 120) laterally offset from said roller and depending to a lower level than said roller for feeding adhesive in the tank to a receiving reservoir (24, 124) associated with the doctor blade (18, 118), the receiving reservoir communicating with an operative part of the applicator roller (16, 160), characterised in that a common rotary axis is provided for the rotation of the pick-up disc (20, 120) and applicator roller (16, 116). Adhesive applicator apparatus according to Claim 1, in which at least one doctor blade is disposed between a slot (24, 124) which forms the receiving reservoir and a further slot (28, 128) which forms an adhesive return reservoir for the return of excess adhesive to the supply of adhesive in the adhesive tank (12,112). Adhesive applicator apparatus according to claim 2, in which, between the slots (24 and 28) which form the receiving and return reservoirs, there is at least one groove (26) above and below which are lands which constitute primary doctor blades (30) spaced from the operative part of the applicator roller (16), and immediately above the slot 28 forming the adhesive return reservoir a part comprising a final doctor blade (32). Adhesive applicator apparatus according to any one of the preceding claims, in which a part of the pick-up disc (20) is flanked by a U-shaped element (22) forming a channel for the flow of adhesive into the slot (24) comprising the receiving reservoir. Adhesive applicator apparatus according to any one of the preceding claims, including an adhesive pick-up limiting doctor blade (123) associated with the pick-up disc (120). Adhesive applicator apparatus according to any one of the preceding claims, in which the at least one doctor blade is formed in a doctor blade assembly (18,118). Adhesive applicator apparatus according to claim 6, in which the doctor blade assembly (118) is located by means of pivotal mounting means within the adhesive tank (12) and abuts against resiliently mounted abutment means. Adhesive applicator apparatus according to claim 7, in which the pivotal mounting means comprise at least two laterally spaced ball and socket arrangements (140). Adhesive applicator apparatus according to either one of claims 7 and 8, in which adhesive return passages (142) extend through the pivotal mounting means to a lower region of the adhesive tank (112). Adhesive applicator apparatus according to any one of claims 7 to 9, in which the doctor blade assembly is acted on by resilient means (119,121) which urge it towards the applicator roller (116). Adhesive applicator apparatus according to any one of the preceding claims, in which the applicator roller (16) is provided with at least one angled ridge (38) extending across an operative part of the roller at the doctor blade contacting diameter of said roller, said angled ridge acting to sweep sideways any particles of material reaching said operative part. Adhesive applicator apparatus according to claim 11, in which there is at least one pair of angled ridges (38) extending in chevron fashion along the applicator roller (16). Adhesive applicator apparatus according to either one of claims 11 and 12, in which the at least one angled ridge (38) is a continuous ridge. Adhesive applicator apparatus according to either one of claims 11 and 12, in which the angled ridge (38) is a discontinuous ridge composed of a plurality of angled ridge elements at circumferentially spaced locations around the applicator roller (16), successive ridge elements overlapping each other across the operative part of said roller.

Inventors: LEVERICK PAUL DAVID, LEVERICK, PAUL DAVID
Applicants: KAYMICH C B & CO LTD, C.B. KAYMICH & COMPANY LIMITED
Application year: 1992
Main classification: A24C5
IPC codes: B05C1, A24C5